Solar Splash Technical Report
Boat #1
05 May 2014
Team Members
Joel Dewhurst
Jacob Dubie
Scott Gay
Joseph Girgis
John Howland
Joel Ingram
Advisors
Dr. Timothy Dewhurst
Dr. Gerry Brown
Trevor Leeds
Luke St Pierre
Nik Schroeder
Jay White
I. Executive Summary
EXECUTIVE SUMMARY
The overall goal of the Cedarville University 2013-14 Solar Boat Team is to win the Solar
Splash Competition in 2014 and to lay the groundwork for future entries in both the Solar Splash
and DONG Energy Solar Challenge (DSC). To accomplish this, we have focused on developing
ways to decrease the weight of the boat by switching to a Kevlar/Nomex honeycomb structure,
increasing the energy available for racing by developing new solar panels with the ability to
capture low angle light, and by increasing the efficiency of our drivetrains by developing new,
lighter weight, more efficient motors. By analyzing the winning performances of past teams, we
set target speeds for 2014 of 38 mph (61 km/hr, maximum speed) for the Sprint event and 9 mph
(14 km/hr) for the Endurance event.
We have developed a textured surface pattern for the solar array that will capture 15% more
energy from low-angle light. We have also reduced the weight of our solar panels by adopting a
manufacturing technique we developed in 2012 for the panels we used in the DONG Energy
Solar Challenge. Our new Sprint drivetrain has an increase power output of 7 kW, a 50% jump,
and our new Endurance drivetrain produces 20% more power (150 W). Our overall weight
reduction for the new boat is approximately 120 lb (54.4 kg, 20%). We developed new propellers
with target efficiencies of 70% and 80% for Sprint and Endurance events respectively.
There are two Major rule changes this year. Power output of student-built solar panels will now
be regulated based upon the manufacturer’s cell specifications, not on measured output as has
been done in the past. A 10% allowance for encapsulant results in a maximum nominal output of
528 W. Our existing 57% efficient (based on nominal power) solar array could only harness 301
W, at best, under these rules.
For the development of a new solar array, we completed an optics study which analyzed the use
of a Fresnel lens versus a prism design for capturing more light at low sun angles. From this
study we concluded that a prism design captures more light at lower angles. We have
successfully molded Teflon prisms, which we predict would increase the amount of low incident
light captured by up to 15%.
A second rule change reduces allowable battery packs from 4 to 2. Both battery packs, however,
may now weigh 100 lb (45.5 kg), whereas for the Endurance race only 66 lb (30 kg) was
permitted in the past. We will use one 9-battery Genesis 13EP set capable of providing 31 kW
under Sprint conditions, and one 3-battery Genesis 42 EP set, which can provide 648 W
(continuous) for the Endurance event. However, we will have to use the 13EP set in one heat of
the Endurance event and the 42EP set in one heat of the Sprint event. We have calculated how
many points we will sacrifice by using one set of batteries in the event for which it is not optimal
and have determined this set up allows the most potential
We have conducted high and low amperage battery testing to determine the most advantageous
battery configuration for the Sprint and Endurance Races, from which we concluded that a 12 V
system is best for Endurance and 36 V system for Sprint. This will allow us to use the two
different types of battery packs in either race. Furthermore, we have developed a technique to
switch to a 24 V system during the Endurance race to provide more speed for passing situations.
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I. Executive Summary
To enable us to transfer energy from one battery pack to another, even while charging with the
solar panels, we have developed a battery charging system that manipulates the thermal sensor
voltage input to the peak power tracking (PPT) system. The purpose of this system is to allow us
to use the ideal battery pack for the Sprint races when we have multiple heats in a single day.
We have developed brushless direct current (BLDC) motors and the necessary hardware to
replace our existing Sprint motors. The motor consists of four BLDC motors on one common
shaft, eliminating our heavy belt drive. Our predicted efficiency for the new motors is 90%,
compared to the previously used Agni motors’ 70% efficiency. The new motor is also 80 lb
lighter and more compact allowing for more convenient storage during the Endurance event.
The move to a 12 V Endurance battery pack (from the 24 V system used in the past) necessitated
Endurance motor testing, which revealed that our old Endurance motor far underperforms what
previous teams thought. Furthermore, at 12 V, the motor was even less efficient. Thus, we
pursued a simple rewind for a 12 V power supply. However, in the process we determined our
existing lamination design could be improved, and the construction technique of welding the
laminations was a cause for inefficiency. Thus, we decided to modify this motor design to
improve the flux density in the laminations and to wind it for a 12 V power supply.
To develop new propellers for the expected increase in power, we developed an understanding of
OpenProp, SolidWorks, and CAMWorks. Using this knowledge we have developed a 3 bladed
Sprint propeller which meets our 70% target efficiency analytically. Using 3 blades eliminates
blade overlap to accommodate the 3 axis mill available.
Using FEA and material testing, we have determined that Kevlar skins on a Nomex honeycomb
core provide the lightest construction schedule while meeting all of our strength requirements
and specifications. We have infused both skins and bonded the skins to the honeycomb core.
Out of the mold, our new hull weighs just under 55 lb, significantly below our target value. The
new solar array will be supported by a similar Kevlar/honeycomb structure that attaches directly
to the hull. This array substructure has an enlarged area in the back to house 6 cells across the
width. The weight of the new solar array and supporting structure is approximately 45 lb.
To further our development in years ahead, we determined to advance our modeling of the boats
using Computational Fluid Dynamics (CFD) using ANSYS/FLUENT. We carried out two-phase
flow, hull drag analysis using a grant from Ohio State University’s Supercomputing Center. We
have performed extensive hull drag modeling using our predicted boat weight of 500 lb,
operating at 9 mph. To validate our numerical results, we developed a technique for applying 6
strain gages on the inside of the Endurance downleg to measure propeller torque and thrust, and
from that to determine hull drag. We then tested the boat on the lake to get results that can be
compared to the CFD results. From this, we found the results to match within 10%. Also, our
CFD results back up previous test results that show that every 50 lb or weight removed from the
boat correlates to roughly a 2 lb drag reduction in the Endurance event.
By reducing the weight of the total boat by 120 lb, increasing the efficiencies of both the
Endurance and Sprint drivetrains, developing a unique solar array surface for low-angle light,
and developing an energy management system, we have positioned our team to meet our overall
goal of winning Solar Splash 2014.
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II. Table of Contents
TABLE OF CONTENTS
EXECUTIVE SUMMARY ...................................................................................................... i
TABLE OF CONTENTS ................................................................................................... iii
PROJECT GOALS AND OBJECTIVES ........................................................................... 1
CURRENT DESIGN AND PROBLEM DEFINITION ..................................................... 2
A. Solar System: ...................................................................................................................... 2
1) Current Design: ................................................................................................................ 2
B.
C.
2)
Analysis of Design Concepts: .......................................................................................... 2
3)
Design Testing and Evaluation: ....................................................................................... 4
Electrical System and Data Acqisition ............................................................................... 4
1) Current Design: ................................................................................................................ 4
2)
Analysis of Design Concepts: .......................................................................................... 4
3)
Design Testing and Evaluation: ....................................................................................... 5
Power Electronics ............................................................................................................... 5
1) Current Design: ................................................................................................................ 5
2)
Analysis of Design Concepts: .......................................................................................... 6
3)
Design Testing and Evaluation: ....................................................................................... 6
D. Hull Design ......................................................................................................................... 7
1) Current Design: ................................................................................................................ 7
2)
Analysis of Design Concepts: .......................................................................................... 7
Figure 47. Transom sample showing marks of failure after being loaded to 6100 in*lb ...... 11
E.
3)
Design Testing and Evaluation: ..................................................................................... 11
c)
CFD Hull Drag Analysis: ............................................................................................... 12
Drivetrain and Steering ..................................................................................................... 13
1) Current Design: .............................................................................................................. 13
2)
Analysis of Design Concepts: ........................................................................................ 13
2) Endurance Propeller: ..........................................................Error! Bookmark not defined.
3)
Design Testing and Evaluation: ..................................................................................... 17
BIBLIOGRAPHY ........................................................................................................................... 1
APPENDICES .................................................................................................................... 2
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III.
PROJECT GOALS AND OBJECTIVES
PROJECT GOALS AND OBJECTIVES
The primary goal of the 2014 Cedarville University Solar Splash team is to win the Solar Splash
competition in June of 2014. In order to accomplish our primary goal of winning, we have set
specific goals for each event based upon the past several year’s winning performances.
Our goal for the Sprint portion of the competition is to complete our run in under 22 seconds.
With our predicted 120 lb reduction in weight from last year’s Solar Splash boat (neglecting
weight of hydrofoils on the 2013 boat) and drastic increase in Sprint motor efficiency, from 70%
to 88% by switching to BLDC motors, we calculate that we can obtain a top speed of 38 mph
(61 km/hr) and achieve an average speed of 28 mph (45 km/hr). Our goal for the Slalom event is
to complete the course in 31 seconds or less. It is somewhat difficult to set our goals for the
Endurance event, as rule changes allow for 100 lb (45.5 kg) of lead acid batteries instead of the
64 lb (30 kg) previously allowed for the Endurance event. Using past year’s data we predicted
that, with our reduced weight and increased power input, our boat will achieve an average speed
of 9 mph (14.4 km/hr). This correlates to a distance traveled of 36.0 mi (57.8 km).
To attain these target times, speeds, and distances, we created a power budget to dictate what
each subsystem has to deliver. Figure 1 shows a visual representation the power budget. The
Direction of
power flow
976 W
Thrust
673 W
Prop
(85%)
789 W
Gear Box
(95%)
Motor
(85%)
Motor
Controller
(99%)
830 W
Control Panel
(Driver Input)
Drag
Driver
MPPT
(97%)
Subsystem name
(Efficiency)
Solar Cells
(19%)
338 W
Batteries
648 W
Amount of Power
360 W
Figure 1. Power flow diagram for the boat
hydrofoil analysis done last year indicated that the existing boat is too heavy. This year we are
cutting weight in the subsystems recommended by last year’s team. We are reducing the weight
of the hull from 105 lb to 55 lb, the Sprint drivetrain and controllers from 155 lb to 70 lb, and the
solar array from 55 lb to 45 lb. The full power and weight budgets are shown in Appendix Z:
Power and Weight Budgets.
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V. PROJECT MANAGEMENT
CURRENT DESIGN AND PROBLEM DEFINITION
To fulfill the Appendix requirements documenting boat batteries, flotation calculations, proof of
insurance, and team roster: we included them in Appendices A, B, C, D.
A. Solar System:
1)
Current Design: The existing solar array has a nominal power of 750 W. However its
output power for standard test conditions is only 425 W. Most of the solar cells are cracked, and
the tabbing wire connections are damaged. The array weighs 55 pounds. It is comprised of
carbon honeycomb backing, supported by an aluminum frame. This array is heavy, and
underpowered due to the new solar array rule.
The new 2014 solar array should achieve an output power of at least 480 W under standard
testing conditions. This is the array limit given in Solar Splash rule 4.2.4. To achieve this the
power output must be within 10% of the nominal power of the array. The array will serve as the
deck for the Endurance race, and not weigh more than 45 pounds
2)
Analysis of Design Concepts: The 2012 team constructed flexible panels for use in the
DONG Energy Solar Challenge. This array produces 81% of its nominal power, Based on these
results, along with the push to cut weight in order to allow the use of hydrofoils in future years,
we decided to pursue a solar array design similar to the DSC array. This design, in addition to
producing closer to nominal power, cuts weight replacing the aluminum frame with composite
panels, that are the same composition as that of the hull, except with a thinner core. The panels
and backing will serve as the deck for the Endurance event
When evaluating the 2012 panels we discovered that there were several encapsulant options that
had better optic properties (allow more incoming light to get to the solar cells) than the EVA that
was used. Particularly, we discovered the FEP Teflon has a much lower refractive index, and a
higher transmissibility than the encapsulants
used in both the 2010, and 2012 arrays. In order
Incoming Light
Reflected Light
to come within 90% of the array’s nominal
power we investigated the use of Fresnel lenses
for our solar array. However, in the morning
Lens
Reflected
races the vast majority of the light is coming in
Light
at a low angle from one direction. Thus we
decided a prism design better addressed our
needs. Figure 2 illustrates this. The triangular
Refracted Light
prisms uniformly bend the incoming light. The
race course is a narrow strip running north and
south; thus the majority of the time the light will
Figure 2. Prism Top Layer Concept
be striking the panels from the same orientation.
We created a spreadsheet to model a prism top layer. This spreadsheet is explained in Appendix
E: Optics Study in Excel. We could then create sample comparison plots to determine the ideal
prism angle. These calculations are based on Snell’s reflection/transmission equations.
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V. PROJECT MANAGEMENT
Amount of Light
Transmitted (%)
Starting with these equations
100%
we completed an optics
80%
study to determine the
S Polarized light
60%
P Polarized Light
benefits of a Fresnel lens top
Average Light
40%
layer. Figure 3 shows the
Brewster's Angle
20%
light refracted into EVA for
various angles incidence.
0%
0.0
20.0
40.0
60.0
80.0
The amount of light
Incedent Angle (Degrees)
transmitted through the
Figure 3: Amount of Light Captured Low Incoming Angles
encapsulant drops off very
quickly from 60° from the surface normal to 90°. This means that when light is coming in at low
angles, which we’ll see in the 9 am Endurance heats, most of the light is reflected.
Amount of Light Transmitted
(% )
This study indicated that prism
120%
angles between 40° and 50° were
100%
optimal, based on the amount of
Morning Races
light captured for the sun angles
80%
we’ll be racing at. We selected 45°
60%
Top Layer With
because it would be easiest to
Triangular Prisims
40%
manufacture. We then plotted a
comparison of a flat top layer and a
20%
Flat Top Layer
prism top layer, with 45° prisms.
0%
This is shown in Figure 4. From the
0
20
40
60
80
figure we can see that for an
Angle of Incoming light (° Measured from veritical)
incidence angle of less than 45° the
Figure 4: Comparison of a flat surface and a surfaced top layer
prism top layer absorbs less light,
with triangular prisms at 45°
but is very close to the flat layer.
However, when the angle of incidence is greater than
45°, all of the incoming light is hitting the prisms on
Series 1: 36 Cells
the side angled towards it, so the relative incidence
Six 2x3 Cells
angle is very low, thus allowing more light to be
refracted. This corresponds to roughly a 20% increase
Series 2: 36 Cells
Six 2x3 panels
in light captured at angles greater than 45°.
Solar cells were decided on based on their nominal
power, and the required deck area. Everbrite offered
cells that were a 1% increase in efficiency over the
2012 cells. The layout of the solar cells was then
finalized, this layout is shown in Figure 5. A system
with three series was selected. This allow one of the
three series to charge on of the three batteries, and
assures the each series has a high enough voltage to
charge the 12 V batteries. The series calculations are
shown in Appendix F: Solar Array Electrical
Calculations. The solar array nominal power is
527.85 W, this is within 0.15 W of the max allowed
nominal power. These panels were then manufactured
Solar Splash Technical Report
Series 3: 28 Cells
Six 2x3 panels
One 3x1 panel
One 2x2 panel
Figure 5: Solar array layout for three
series
3
V. PROJECT MANAGEMENT
according the procedure laid out in Appendix G: Creating the Solar Array Series. We created a
sample platen, and molded Teflon, this indicated that using Teflon for the surfaced top layer is
feasible. Figure 6 shows this molded Teflon.
We then created samples using a one-step
lamination process. This is laid out in
Appendix H: Molding Teflon. Both samples
Figure 6: Molded Teflon, with fully formed prism
indicated that a one-step method would likely
peaks
be infeasible. It was thus decided that a twostep method, in which the Teflon is formed first, at 290°C, then that lamination performed at
149°C (300°F), which is the melting point for EVA, would work best.
3)
Design Testing and Evaluation: We evaluated our surfaced top layer design
analytically. Our optics study predicts ~20% increase in light captured at low incoming angles.
Once a cell with a perfected top layer is completed, we will validate this experimentally. We will
measure its power output compared to a flat top layer cell, at the varying angles of incidence,
specifically when the light is overhead (0°) and when the light is coming in at 30°-40° (light
conditions for the morning races). If the increase in light captured is close to what is expected
based on the optics study, then the rest of the array will be manufactured with the surfaced top
layer. Once the entire array is manufactured, then each panel and series will be tested using our
transistor bank to vary the current being drawn from the panels, and measure the corresponding
voltage. Temperature and sun light conditions will be measured in order to normalize the data to
standard test conditions.
Overall loss of
We have been testing different methods of forming
transmissibility
the surfaced top layer. We first tested the use of
EVA, and conformal coat as encapsulants. Both of
these formed easily, but would not release cleanly.
Whiteness caused
We then evaluated the use of Teflon as a top layer,
by separation of the
this releases easily, but is hard to form, and loses its
EVA and Teflon
high transmissibility if it gets too hot. Figure 7
Figure 7. Sample using Teflon to form the
shows these problems. We are currently
surfaced top layer
manufacturing test samples with Tefzel as a top
layer. Tefzel is designed to release from molds, and is melt process able.
B. Electrical System and Data Acquisition
1) Current Design:
The existing Electrical system consisted of two separate integrated circuit boards for Sprint and
Endurance. Data we recorded using NI data acquisition via LABView Signal Express. The motor
was controlled directly by a servo tester on the dashboard. The current system is inefficient,
because of the separate boards and difficulty reading data.
2)
Analysis of Design Concepts: To fabricate an integrated circuit capable of performing
the follow tasks: collect and Store/Transmit data at appropriate speeds; interpret strain gauge
data for torque and thrust gauges; Send and receive logic between the complex programmable
logic device (CPLD) on the battery controller circuit (BCC), and send appropriate signals to the
motor controllers.
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V. PROJECT MANAGEMENT
We run the board on 12/24 V coming from the BCC, depending on which mode we are in. We
power the board with 3 voltage regulators of 3.3V, 5V, and ±12V. All of the signals going into
the Max32 will be between 0 and 3.3 V, because of input constraints.
a) Store/Transmit Data: We use a Bluetooth to phone system to transmit data to a server
as our main means of storing data, with an SD card as backup. We have a GPS on the board,
telling us position, speed and acceleration. The Bluetooth, GPS, and SD card communicate using
the RX and TX pins. All of our signals will be processed in the ChipKIT Max32 Microcontroller.
The language of the Max32 in a modified version on Arduino. The Max32 can operate at
frequencies up to 80MHz, where is more than sufficient for our needs.
We have the following analog signals going into the Max32; Peak Power tracker (PPT) current
for solar array 1, 2, 3, and the battery voltage for each of the three batteries, the total battery
amps, and the Tachometer signal. For all of the analog signals, except the battery voltages, we
used a voltage follower circuit. For the battery voltages we used a differential op-amp circuit.
We have the overall battery voltage and current running directly to panel displays in case the
Max32 fails during competition.
b) Strain Gauge Data: The strain gauge data will come from 4 strain gauges for torque
and 2 for torque. Our task was to create a robust circuit that can detect the differential voltages to
3.3𝑉
3.3𝑉
the strain gauges, while maintaining an offset of 2 . To do this we run 2 through a voltage
follower, to an inverting buffer. We also send the strain voltages through a differential amplifier
with gains of 11.9 or 6.0, depending on which jumpers are connected. Both of these signals are
3.3𝑉
sent to another diff amp with a gain of 1, giving signals with an offset of 2 .
c) CPLD Logic send and receive: We have 5 variables the driver can change; 12V, 24V,
36V, Motor, and Deadman. Each of these circuits run to switch on the driver dashboard and sent
to the BCC. We also will receive the four state variables from the BCC.
d) Control Motor Controller: The Max32 will read a pot voltage from the dashboard and
this will indicate what percentage of current we want going to the motors. This will be sent over
the communication line to the Current Controller Cards (CCC) s. We have a servo tester as a
back-up going directly to the CCCs with a voltage follower, allowing us to run four motor
controllers with the same signal.
A detailed discussion of the circuitry can be found in Appendix Y: Electronics
3)
Design Testing and Evaluation: The board successfully read all of the analog signals
and all of the Max32 inputs were between 0 and 3.3 volts. The strain gauges had sufficient gain
to successfully measure the maximum amount of strain without saturating. The voltage
regulators were sufficiently smooth as well. The Max32 can sufficiently control the current by
knowing the current state of the system.
C. Power Electronics
1)
Current Design: The Sprint system 36 V, with nine Genesis 13EP connected through
Sevcon controllers to two Agni motors. The Endurance system is 24 V, with two 42 EP
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V. PROJECT MANAGEMENT
connected through an ICE controller to a Podded Propulser unit. The battery rule change makes a
24 V system infeasible with the batteries we have.
2)
Analysis of Design Concepts: Our task is to create system that can operate in 12V,
24V for endurance and 36V for sprint. We need a circuit capable of switching the system from
12V to 24V for endurance, from the dashboard, and to successful control the system.
We achieve this by have a complex programmable logic device (CPLD) synthesize the inputs
from the master instrumentation card giving us the state of the system. The CPLD will also
output logical bits to MOSFET 110 A switches inside the battery controller box (BCB). These
switches will be responsible for switching between the different racing modes.
We also designed a circuit that can transfer power from one battery box to another, because of
the constraint to having two battery boxes in competition.
We also control the current controllers, by sending signals to the current controller cards from
the MIC. The CCC will consist of an Uno32. It will use a feedback loop that can detect how
much current is flowing in each system and adjusts the PWM signal accordingly.
a) CLPD Logic: The Main inputs going into the CPLD will be the 5 switch signals from
the MIC and four signals on the BCB; charge/being charged, End/Sprint, Aux charge, and
Instruments. With these 9 different signal the CPLD will determine the current state of the
system. We used a finite Moore state machine with all nine inputs for the basic structure for the
system.
The state machine has 15 states. The various states necessary are Idle states for each mode,
prechargeing states, and racing states. Each of these states has a different combination of outputs
for the switches in the BCB.
b) PCB switching circuit: The difficultly of the switching circuit lies in the fact that we
want to switch from 12V to 24V, while we are racing the boat. We do this by taking one of the
batteries out of the parallel combination of all the batteries, then putting that one battery in series
with the other two. This is done by a specific sequence of switches.
Most of the different modes consist of pre-charge circuits that limit the current using a shunt
resistor. The state switches back to a short circuit after a pre-determine time. This time is predetermined in the CPLD.
c) CCC: The current controller schematic can be seen in [] and the PCB layout in [].
The CCC mainly has one communication line coming from the MIC to the Uno32 on the CCC.
The Uno32 will then generate its own PWM signal, and it will adjust the PWM based on the
current sensor data.
The board will also take the temperature data from RTDs and detect the temperature of each
motor controller with a Wheatstone bridge configuration.
A detailed discussion of the circuitry can be found in Appendix Y: Electronics
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V. PROJECT MANAGEMENT
3)
Design Testing and Evaluation: When we first tested the CLPD logic, we realized that
when the batteries get connected in a parallel combination, there was a huge surge in current
between the batteries that exceeds the 110 Amp current limit for the FET switches, so we needed
to add another sequence of switching to the 12 V pre-charge state.
We also realized that we needed a pre-charge state from 24V race back down to 12V race. We
already had one for 12V race to 24V race, but we didn’t anticipate on needing a step down
D. Hull Design
1)
Current Design: The existing hull was designed in 2004. It was built in 2006 out of
cedar strip overlaid with fiber glass. It weighs in excess of 105 lb. A lighter hull can be made
using a nomex honeycomb core.
The existing design for the Solar Splash hull shape is very good and will not be modified. We
will, however, utilize a composite construction schedule to reduce the weight of the hull, which
will help us to achieve one of two primary goals outlined for this year, weight reduction. Our
overall goal for the new lightweight construction is to reduce the weight of the hull to 55 lb
(25 kg) or less, down from 105 lb plus (48 kg) for the existing hull (48% weight reduction).
Also, the hull must be watertight, weigh under 53 lb (24 kg), be able to withstand hitting bottom
at speeds under 10 mph (16 km/hr) without puncture or tear (sandy bottom), and be aesthetically
pleasing. Since our new hull will compete in the Sprint and Slalom events without the deck
attached the hull must meet certain strength and stiffness requirements as follows: the hull must
strong and stiff enough such that, for any of the four cases modeled using FEA (covered in the
Design Methodology portion of this report), the hull never deflects more than 1 in and maintains
a safety factor of at least 5 based on our numerical solution.
We will improve our computational fluid dynamic (CFD) capabilities to enable drag predictions
using a volume of fluid (VOF) 2 phase flow. Our results shall be within 10% of the actual drag
data. Also, to run these models we will need increased CPU computing power. These results will
be validated using strain gages mounted inside the Endurance downleg.
2)
Analysis of Design Concepts:
a) Hull Construction: In order to construct a new hull which meets the conditions laid
out in the Current Design portion of the report, many sub-tasks had to be completed. The key
tasks which we sought to complete were as follows: 1) predict required strength, 2) select
materials for testing, 3) perform material testing, 4) make final composite schedule selection, 5)
select and perfect manufacturing technique, 6) manufacture hull, and 7) perform testing and
evaluation.
Once we had completed our background research into lightweight hull construction, our first
course of action was to complete a finite element analysis (FEA) of the hull using SolidWorks
Simulation to determine the required material stiffness, core thickness, tensile strength, and
determine if interlaminar shear stress might cause delamination between the fabric skin and core.
First, we identified several loading cases for which we could expect the most extreme loading of
the hull to occur. Those loading cases of the hull which we identified as being the most extreme
were: 1) during Sprint event, 2) on trailer, 3) when lifted from bow and stern, and 4) with torque
applied at bow. For more information on how we applied loads and boundary conditions, defined
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V. PROJECT MANAGEMENT
and created our mesh, and analyzed and interpreted our results please see Appendix Q: FEA of
Hull without Deck Attached.
Based on our results, for the 4 cases we modeled the maximum principal stress never exceeded
1500 psi in compression (safety factor of approximately 10 for selected composite schedule). We
concluded that the stresses under standard operating conditions are not very high and impact
resistance, lightweight construction, and rigidity were more critical than tensile and compressive
strength.
Based on our FEA, we selected various composite materials (carbon fiber, carbon/Kevlar biweave, Kevlar, and fiberglass), as well as a Nomex honeycomb and infusion ready
polypropylene honeycomb core (foam and balsa wood cores were not considered because of
their higher density than honeycomb cores) for testing. We then proceeded to establish testing
methods (tension, short beam, 3 point bend, and impact) and perform material testing. See
Appendix R: Mechanical Testing of Hull Materials for more information on tests performed.
Kevlar and carbon fiber exhibited similar ultimate tensile strengths, while fiberglass had an
ultimate tensile strength of less than half that exhibited by Kevlar and carbon fiber. Thus, we
excluded fiberglass from serious consideration. Also, Kevlar had a slightly lower Young’s
modulus than carbon fiber. This reduction in stiffness, however, can be easily accounted for by
increasing core thickness, resulting in a Kevlar hull of equal stiffness to a carbon fiber hull with
very little increase in weight. Since the core material used in the new hull (except the transom)
weighs only 1.8 lb/ft3, doubling the core thickness from 0.5 inches to 1.0 inch results in a weight
increase of approximately 5 lb (2.3 kg) for the entire hull, and more than accounts for the
reduced stiffness of Kevlar.
We also confirmed that interlaminar shear causing delamination of fabric and core was not an
issue under standard high shear conditions. We did find, however, that delamination occurred
under impact. We also found that under high impact loading Kevlar greatly outperformed both
carbon fiber and fiberglass, exhibiting a much greater resistance to delamination and a much
greater impact toughness.
The carbon/Kevlar bi-weave, which we were hoping might provide both the stiffness and impact
toughness desired, while performing better than carbon fiber under impact, was still drastically
outperformed by a pure Kevlar fabric and was eliminated from consideration. Finally, of the two
resins being tested, MAS Low Viscosity Epoxy resin proved much less brittle than Adtech 820
resin. Also, the MAS resin systems had a lower viscosity, allowing for better resin flow during
infusion. Thus, we selected Kevlar and MAS Epoxy resin systems for constructing our hull.
The infusion ready polypropylene honeycomb core proved too heavy for any use except the
transom where it will replace the previously used, and heavier Coosa board for a weight savings
of 3 lb (1.4 kg). We will use a Nomex honeycomb for the rest of the hull.
Solar Splash Technical Report
8
V. PROJECT MANAGEMENT
We then ran a final FEA of the worst case scenarios for
deflection using our experimentally determined material
properties. This analysis indicated that a 1 inch core was
sufficient to meet our strength and stiffness requirements.
Also, using a 1 inch (or thicker) core met the Solar Splash
buoyancy requirements without using bulkheads, or other
means of buoyancy. Due to the materials available for
donation, we used 1 layer of 1.25 inch honeycomb from the
transom up to 165 inches from the transom and 2 layers of
0.472 inch honeycomb core for the bow (see Figure 7).
Additionally, we will utilize wooden gunnels for increased
stiffness, aesthetics, and providing a means of attaching the
steering system and deck.
1 layer 1.25”
honeycomb
Transom - 165”
2 layers 0.472”
honeycomb
165” - Bow
Figure 7: Honeycomb core material
With our composite schedule selected, we then established
cut
to patterns and laid on outer skin
our manufacturing method. The three options available were
hand layup, vacuum bagging, and infusion molding. Based on previous year’s experiences we
sought to avoid vacuum bagging using pre-preg (pre-impregnated) fabric for the following
reasons: porosity, lack of an oven large enough for curing, and expense. This left us with the
options of hand layup and infusion molding. We had an average mass ratio of fabric to resin for
hand layup of 33:67 and 55:45 for infusion molding. Thus, infusion molding proved the far
better option for manufacturing a lightweight hull. This causes issues, however, when using a
honeycomb core that is not infusion ready, as air pockets in the honeycomb would fill with resin
during infusion. Through further experimentation we determined that the best method for
producing a lightweight hull was to infuse each skin separately, sand the bonding surface of each
skin, apply a thin coat of resin using a paint roller, and use light vacuum pressure to provide a
constant force between skins and core for the best bonding. This was the method chosen for the
2014 Solar Splash hull. See Appendix S: Hull Manufacturing Techniques for a further
explanation of the manufacturing technique selected and images of hull manufacture.
b) Internal Strain Gage Application: In past years we mounted strain gages on the outer
surface of the Endurance downleg to measure drag. This year, however, we mounted the strain
gages on the inside of the downleg to protect them from damage.
We considered several concepts including: a small car-jack like mechanism, balloons, and a
mechanical device with a slider to apply the gages. We dismissed the car-jack mechanism for
complexity and size constraints and the balloon concept because we feared pressure might be
lost. Thus, the sliding mechanism concept was chosen for further investigation.
Solar Splash Technical Report
9
V. PROJECT MANAGEMENT
Through several iterations, we
Single Grooves
designed a sleeve to slide inside the
downleg with slots for the strain
Ramped Plunger
End
gages and strain gage wires to
protect them from the power cables
to the Endurance motor. Also, a
plunger was designed to fit exactly
inside the sleeve and force the
strain gages tight against the inner
Hole for Plunger
Rod
surface of the downleg when
Figure 8. Final Design for the Strain Gage Mounting Device. This
inserted. Figure 8 shows the final
assembly
shows 3 views for the device laid out for the 3D Printer to
strain gage mounting device. All
print everything at one time.
parts were of the strain gage mounting assembly were 3D printed for quick and simple
manufacture and lightweight. Calibration of the strain gages is shown in Appendix W: Initial
Strain Gage Test.
c) CFD Analysis: To predict the drag force on our boat we utilized Fluent and ICEM to
model dual phase, viscous flow (determined by speed, boat length, and dynamic viscosity of
water). We first imported our model into
ICEM from SolidWorks and meshed the
part. Due to the complex geometry of
Meshed Boat Geometry
the hull, we utilized a volume mesh with
Structured Mesh
in ICEM
tetrahedral elements for the region
immediately surrounding the hull in
place of the structured mesh used for the
Flow
remaining meshed region. Due to
Outlet
limitations, we were limited to 512k
cells for any solutions run at Cedarville.
Flow
Volume Mesh
For larger meshes and obtaining more
Inlets
Surrounding Hull
accurate results, we utilized the Ohio
State Supercomputer (OSC). See Figure
Figure 9. Mesh generated using ICEM showing structured and
9 for an image of the mesh used. The
unstructured volume mesh regions
meshed part was then imported to
Fluent where we defined the flow speed at 9 mph, determined by the power budget for the
Endurance event, and specified solver type and other inputs (see Appendix S: Fluent Input
Conditions). For results, see the Design Testing and Evaluation portion of the report.
Solar Splash Technical Report
10
V. PROJECT MANAGEMENT
3)
Design Testing and Evaluation:
a) Hull Construction: As previously mentioned, we
used infusion ready polypropylene honeycomb for the
transom in place of Coosa board for a 3 lb weight
Failure
reduction. A test sample with a 0.5 inch infusion ready core
withstood 6100 in*lb (691 N*m) before a split appeared in
the inner skin and deflections of 1-2 inches were observed
(see Figure 10). The loading withstood by the infusion
Figure 10. Transom sample showing marks of
grade
failure after being loaded to 6100 in*lb
Table 1: Predicted and actual weight to date. Both fall
core
underneath the target weight of 53 lb
was greater than the moment produced by the
motor (4500 in*lb predicted). By using a
Weight [lb]
Type
Item
1 inch thick core with gunnels, we increased
Predicted
Actual
our safety factor and reduced deflections
Gel coat
5.0
(0.25 inches or less predicted).
Outer Skin
5.6
14.6
Outer
Inner
Other
Transom
Sub Total
Inner Skin
Sub Total
Nomex Honeycomb
Bonding Fabric
Gunnels
Sub Total
Total
3.5
14.1
5.6
5.6
14.7
5.0
10.0
26.7
49.4
14.6
6.2
6.2
13.6
6.6
N/A
20.2 (30.2)
41.0 (51.0)
As outlined previously, we infused the inner
and outer skins and bonded them to the
honeycomb core by applying resin to the
skins and using vacuum pressure to provide a
bonding force between the skins and core. In
regards to predicted, target, and actual weight
please refer to Table 1, which indicates that
our predicted and actual weights are almost
the same.
Testing indicates that our hull is as stiff as we predicted and meets our stiffness requirements.
Once we have completed construction, we will test the new hull on the water to ensure that it
does not have any issues with leakage. We will also weigh our new hull to ensure that we
reduced the weight of our hull either to under 55 lb, our target weight, or at least under 105 lb,
the weight of the existing hull.
b) Internal Strain Gage Application: We first confirmed that our strain gages had
adhered to the downleg and gave linear results when a load was applied. For more on the results
of the initial strain gage test see Appendix W.
Once the gages were successfully mounted inside the downleg they were characterized such that
we could calculate applied load from the strain values measured by the gages in order to
determine drag. For details see Appendix X: Final Strain Gage Test and Characterization.
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V. PROJECT MANAGEMENT
c) CFD Hull Drag Analysis: Using the mesh defined in Analysis of Design Concepts,
inputs defined in Appendix S: Fluent Input Conditions, and water levels determined using
Appendix AA: Center of Gravity Software we obtained converged solutions using Fluent. Figure
11 shows the waveform pattern obtained when the bow is initial submerged 9.5 inches and the
transom is initially submerged 3 inches (hull
weighs 500 lb). Figure 12 shows the actual
wave pattern created during the Endurance
event for a 600 lb boat.
Figure 11. Waveform pattern for 500 lb boat. Red
With our ability to obtain converged and
reliable solutions, we then varied the water
level while maintaining a constant weight as
prescribed by the weight budget in order to
determine the optimal center of gravity
(COG) location. Based on these results,
running with the transom submerged
3 inches at rest is the optimal point.
designates air, blue designates water, and green designates
the transition region between phases. The thin black line
dictates the starting water line in Fluent.
Figure 12. 600 lb Hull during 2013 Solar Splash
competition showing the water level and wave pattern
during the Endurance event. There is a good correlation
between the Fluent’s predictions and actual results
We then analyzed the effect of weight on
hull drag using the optimal, transom submerged 3 inches at rest parameter. Figure 13 shows the
results six different weights at that parameter. We see a linear relationship between drag force
and boat weight. The offset between a weight of 500 and 530 lb appears to be influenced by the
wave pattern at the chine line. From this test we concluded that 50 lb correlates approximately to
2.5 pounds of drag. See Figure 14 for several waveforms obtained from these results.
30
29
27
Drag Force [lb]
7.0 inch Bow Depth – 608 lb
Boat Weight
y = 0.0496x - 2.0185
R² = 0.9989
28
26
25
5.5 inch Bow Depth – 499 lb
Boat Weight
y = 0.0495x - 0.0962
R² = 0.9946
24
23
22
21
20
400
450
500
550
600
650
4.5 inch Bow Depth – 429 lb
Boat Weight
Weight of Boat [lb]
Figure 13. Drag force vs. Weight of boat when
transom is submerged 3 in. This is the plotted data
extrapolated from Fluent.
Figure 14. Waveforms obtained during weight vs. hull
drag testing.
After performing an experimental test, we realized our CFD model did not include enough detail
to accurately predict the drag force as the actual drag of 50 lb obtained using the strain gages did
not match the 30 lb. The driver, downleg and propeller, solar panels, and the empty cavities in
the boat were not modeled.
Due to issues with the Endurance drivetrain, we could not perform more testing at the time.
Therefore, we used boat drag data from the 2008-2009 Solar Boat team to verify our model in
Fluent since the 39 lb they measured seemed more trustworthy the 50 lb we measured.
Solar Splash Technical Report
12
V. PROJECT MANAGEMENT
To determine the effect of various parameters,
we remeshed our hull as open, with no deck
attached. With the deck removed, our predicted
drag force is 36-38 lb, very close to the
observed 39 lb of drag. Figure 15 shows
streamlines of the boat without the deck.
Figure 15. Velocity streamlines on the Solar Boat
E. Drivetrain and Steering
without the deck on. Flow over the transom creates
1)
Current Design: Our steering is a
much drag. Additionally, the flow behind the boat is
very slow and turbulent.
cable and pulley system. It is light weight and
provides good handling. We are not making any
changes to it. The Sprint drivetrain, Endurance drivetrain, and propellers are all being updated.
a) Endurance Drivetrain: The Endurance motor is rated to run at 87% efficiency at 4000
RPM. However, based on testing done this year, the motor’s efficiency was only 75% while
operating at 3000 RPM. The 2011-12 power budget for the motor is 7.6N-m (5.6 lb-ft), with a
motor drive voltage of 21V. We are hoping to increase efficiency of our motor by at least one of
three options. Since this is the motor operating speed at which the propellers are most efficient,
we must increase the efficiency of the motor at this operating point.
b) Sprint Drivetrain: The existing Sprint Motor design is comprised of two 25 lb Agni
brushed DC motors. These motors are mounted top and bottom, and drive a common shaft to a
15 lb 2.8:1 Gates belt drive transmission. The Agni motors operate at roughly 1200 rpm full load
giving an overall prop speed of roughly 3600 rpm. The overall system weighs 154 lb and is
approximately 70% efficient. The incentive behind a redesign of the Sprint motor is threefold:
increasing efficiency, reducing weight, and enhancing storage ability during the Endurance
Event.
The design specifications pertaining to the Sprint drivetrain this year are to increase system
efficiency to 90% or greater, to reduce the system weight to 70 lb or less, and reduce the motor
size to a maximum of 12” x 10” top-view footprint to facilitate storage of the motor during the
Endurance Event.
c) Propellers: The For this competition, two different propellers will be designed, one
for the Sprint and one for the Endurance event.
2)
Analysis of Design Concepts:
a) Endurance Drivetrain: For the first semester our main objective was to test the
efficiencies of the existing 24 V Endurance motor at lower voltages to find out how the
efficiency of the motor is affected. Since the Endurance Motor is actually wound to operate at 21
V, but the team actually operated the motor at 24 V it was believed by Professor Dr. Brown that
the extra 3 volts used led to unnecessary power being used to spin the rotor. In order to conduct
our tests, we were required to understand the testing equipment that we would be using such as
the National Instruments (DAQ), the Lab View program it interfaced with, and the Magtrol
Dynamometer. The majority of our testing was executed to determine efficiency. This was done
by recording input power (Pin) to the Endurance motor, by recording current and voltage. Output
power (Pout) from the Dynamometer was calculated by recording torque and speed.
Solar Splash Technical Report
13
V. PROJECT MANAGEMENT
The Efficiency of the motor was tested by measuring the torque output. We set the Dynamometer
(Eddy Current Brake) to spin at a specified speed. Using the Speed Reference connected to the
motor we increased the speed, however since the Dyno is set for one speed, a brake is applied,
not allowing the motor to spin faster than the specified speed. Therefore as speed of the motor
increased the Dyno would apply more torque to keep it at a constant speed. By utilizing the
output power (Pout) recorded by the dynamometer, and comparing it with the power input
recorded by the DAQ, we calculated efficiencies for varying torques on the 24 V system at
constant speeds of 500, 600, and 700
RPM. We then utilized a variable power
85
supply which allowed us to test across a
80
range of voltages from 13.5 to 24 V.
75
Efficiency [%]
We continued torque efficiency testing
without the gearbox at voltages less than
21.Results of tests run at 21, 18.5, and 15
volts showed that efficiency increases as
we operated at lower voltages as shown
in Figure 16. This gave us confidence
moving on with a 12 V system because
due to the rule change of only being
allowed to have two battery packs, we
decided it would be more convenient to
work with a 36 V (sprint motor) and 12 V
(Endurance) instead of a 21 V or 18 V
system.
70
15 V
Corrected
65
18.5 V
Corrected
60
55
21 V
Corrected
50
45
0.0
0.5
1.0
1.5
2.0
Torque [Nm]
2.5
3.0
Figure 16. Efficiency torque curve for voltages of 15, 18.5, and
21 V, at 3000 rpm
Amperage [A]
Having made the decision to rewind for 12 V, we were able to find an outside source who was
willing to rewind and test the motor for us. However, problems arose when we discovered that
the no load current was higher than expected (7 amp no load current for 12 V system). By further
analyzing our data, we realized that this was
70
consistent with our own data which indicates
60
that decreasing operating voltage increases no
50
15 V
load current as shown in Figure 17 At this
40
increased no load current the motor quickly
30
18.5 V
overheated due to inefficiencies in the motor
20
21 V
design.
10
0
We then made a new motor which addressed
0
1
2
3
4
Torque [Nm]
these inefficiencies. This included removing the
Figure 17. Current Torque curves for 15, 18.5,
welds that connect the stator, removing two
and 21 V, at 3000 rpm
thicker laminations at the end of the stator
which were causing eddy current losses (loss of
10% efficiency), and redefining the dimensions of our yoke and pole width to create an even flux
density.
Solar Splash Technical Report
3.5
14
V. PROJECT MANAGEMENT
b) Sprint Drivetrain: The motor design was heavily dictated by three restricting factors.
These factors were the battery voltage and current ranges, motor and controller peak power
ratings (and time constants), and price/weight budgets. The current range was determined by
dividing the full load battery voltage from the available power estimated in the power budget,
and confirmed when found by battery run-down
Stator Assembly
tests that the batteries can deliver 1000-1200 A
continuously for the 25 second race.
Centering Ring
The simplest controller configuration is to
operate four separate motors each with their
End Bell
own controller (~300 A per controller). This
meant that our four motors needed to be
coupled in some manner. We found that there
were a number of viable motors that would
operate at our operating conditions from our
brushless motor designer/supplier. A few motor
and parts configurations were iterated through
Figure 18. Final design of four coupled motors and
to converge on a final design. These motor
water chilling jackets. (motor wires and water jacket
iterations were an integral process in the design
fittings/tubing are not shown for simplicity).
stage, and can be seen and described in better
detail in Appendix M: Motor Layout Design Iterations. After a significant amount of research
and design work we chose to develop a single motor, which is comprised of four attached stators
along with four rotors which are mounted on a common shaft. Each of the motor’s stator
housings will be water-cooled and mounted in a larger housing. The motor assembly model can
be seen in Figure 18. An exploded view showing the individual parts in further detail can be seen
in Appendix N: Final Sprint Motor Design & Parts.
We found a controller that operated at 300 A however did not have over-current protection.
Therefore we will be generating the PWM signal for the controller and automatically changing
the pulse width delivered to limit the current. This is further explained in the Electrical Systems
section in the report.
Magnet
The rotor shaft was
Rotor Assembly
s
Back Iron
designed to be a long
tubular shaft, which
can be seen in
Shaft
Figure 19. This is
Bearing
because the inner
Aluminum
diameter of the stock
Sleeve
back iron for the
magnets of the motor
series we decided on,
supplied by our
Figure 19. Assembly of coupled rotors on motor shaft, also showing a cross section
brushless motor
of a single rotor assembly.
manufacturer, is large. To reduce weight of the shaft we decided to use a tubular shaft. To
increase the rigidity of the shaft and the critical frequency of the shaft, we had to iterate the
design of the shaft thickness. We required a shaft that would not whirl at high rates of speed.
Solar Splash Technical Report
15
V. PROJECT MANAGEMENT
With the diameter of the shaft allowed to be fairly large it permits the wall thickness of the shaft
tube to increase. This in turn increases the rigidity of the shaft. With the increased polar moment
of inertia the critical frequency increases linearly.
The motor housing was the second largest design hurdle to get over, after settling on the proper
motor controller. The stators are going to be mounted in place axially, and each rotor must be
centered (axially) within each stator. Otherwise the net force permanent magnets would exert an
axial load (pushing or pulling the rotor out of place) due to the stators not being directly above
the rotor magnets. The stator housings, when stacked and bolted together, must be concentric,
within a few thousandths of an inch, throughout the length of the entire motor housing assembly.
This must be true because an untrue assembly of stators (non-concentric) would not only exert an
unbalanced radial force exerted by the magnets, it would also (most likely) cause vibration when
operated at our motor target speed. The air gap between the rotor and the stator is 0.03 inches, so
any vibration could be catastrophic if the rotors collide with the stator poles. This means that
machining four separate motor housings could be problematic because any dimensions within
tolerance, but close to perfect, could add together as these motor housings are bolted together.
On the contrary, a second option is also problematic in that boring a single motor housing at this
size would be extremely difficult and expensive. The other issue with one motor housing, is that
if a repair needed to be made to any one stator the only way to access it would be to debond
(melt the cement) of all the stators from motor housing. This heat to remove the stators runs the
risk of demagnetizing the permanent magnets. For these reasons we went with four separate
motor housings coupled together.
Example Windings
Water
This stator housing, which is seen in
Cavity
Figure 20, will have a water jacket
around the outer circumference to act
as a heat sink since almost all the heat
loss of these motors is through the
mass of the stator housings. The
original design of the heat sink
involved winding a copper tube around
Water Jacket
the circumference of each separate
Figure 20. Motor housing, showing wound stator bonded
motor housing and using a pick up tube
inside and external water jacket design.
under the boat to force water up into
the heat sink. This design was decided against because of the
greater heat transfer in the water jacket design.
c)
Propellers: To design the propellers for
the new hull and drivetrains we used designs from
the past, and altered those them to fit the current
power requirements.
The 2012 Sprint propeller has a predicted efficiency
close to 78%. Using this design we modified the
chord over diameter (c/D) ratios and the propeller
diameter (D) to change the area of each propeller
blade, we created the prop shown in Figure 21
which illustrates the final design to date. This
Solar Splash Technical Report
Figure 21. 4th 3-Blade design consideration
intended to increase efficiency and reduce
area between blades
16
V. PROJECT MANAGEMENT
design ideally will operate at 72% efficiency, and has reduced blade area to be machined easily
on our 3-Axis CNC.
We designed a new Endurance propeller that will
better suit this year’s power budget, seen in Figure 22.
This new design is smaller in diameter and blade area
and is designed to operate for this year’s power budget
requirements
Using an output from OpenProp, we created a 3D
model which was then imported into CAMWorks to
create the g-code required to machine the propeller.
This g-code can be tested before manufacturing has
occurred in CAMWorks using the “simulate toolpath”
function. An
example of
CAMWorks
Figure 22. Endurance propeller
simulating
the tool path designed with a diameter of 14.3 inches
can be seen in and smaller blade area than the Dong
Solar Challenge propeller
Figure 23.
Using our
CNC mill we attempted to create a propeller out of
wood. Due to repeated problems in the manufacturing
process, we began to use stacked MDF instead of pine
Figure 23. CamWorks simulating tool
paths to assist with tooling parameters
wood assembled from 2x12 building materials.
3)
Design Testing and Evaluation:
a) Endurance Drivetrain: To date, there is no new Endurance motor to test. The new
motor is being fabricated in California. In Figure 24 shows the results of the efficiency testing
done first
semester. We
can see that
there is an
increase in
motor efficiency
as we decrease
the voltage.
However when
voltage gets very
low, as in the
13.5 V test, we
can see that the
motor is not able
to produce
Figure 24. Torque Efficiency Test of 24 V Motor with Gear Box @ 600 RPM
enough torque.
Solar Splash Technical Report
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17
V. PROJECT MANAGEMENT
b)
Sprint Drivetrain: To During the design stage of the motor, a TK Solver program was
used to analyze the critical speeds of the shaft. Tables that compiled all of the parts required,
system parameters, costs, and a solid model were used to evaluate each design. Each setup was
critiqued to determine any downfall or deficiency, and any benefits until the final configuration
was converged upon. The company we consulted had numerous recommendations throughout
the design phase which guided the development to the final design. This design can be seen in
Appendix N: Final Sprint Motor Design and Parts. When the Sprint motor manufacture and
assembly is complete, the motor will be mounted on the boat and run at no load to test all
electrical systems, observe motor and controller temperatures, efficiencies, and data acquisition.
After these tests are conclusive full load tests will be conducted on water.
c)
Propellers: The most recent design of the sprint propeller, shown in Figure 28, exceeds
design parameters in efficiency and speed. Originally constrained to be a minimum of 70%
efficient while propelling the boat at 36 mph (57.9 kph), the propeller will ideally be 72%
efficient and propel the boat at 37.4 mph (61.2 kph) when operated at the conditions outlined in
the power budget.
The proposed endurance propeller design, shown in Figure 30, also exceeds the design
parameters in efficiency and speed. The original constrains for the endurance propeller was 81%
efficient and propelling the boat at 8.5 mph (13.7 kph). The proposed design will be 84%
efficient and propel the boat at 9 mph (14.5 kph) when operated at the conditions outlined in the
power budget.
PROJECT MANAGEMENT
F. Team Organization
Cedarville University’s Solar Splash teams have primarily been composed of senior mechanical
engineering students as part of their capstone courses, Mechanical Engineering Senior Design I
and II. This year, the team consisted of eight seniors ME’s and two junior EE’s. We were able to
update all of the boat’s major systems. The team was split up into three sub teams.



Hull and Solar Array
Power Electronics
o Energy Management
o Endurance Drivetrain
o Sprint Drivetrain
o Propellers
Electrical System/Data Acquisition
The whole team met for two hours each week to discuss progress. Each sub team met for one
hour each week, to discuss design strategy.
Our team is advised by two faculty members: one mechanical engineer and one electrical
engineer. In a paper written by our faculty advisors, Dewhurst and Brown (2013), they explain
their approach to advising in light of three different educational models: the teacher-student
model, the manager-engineer model, and the master-apprentice model. They attribute much of
the solar boat team’s past success to the mentoring—which balances different aspects of each of
these three types of relationships—that they have provided as faculty to students on the solar
boat team.
Solar Splash Technical Report
18
V. PROJECT MANAGEMENT
G. Project Planning and Schedule
We organized this year’s team in August 2012 and developed a Gantt chart as an estimate of
project and task completion dates to facilitate the completion of team objectives. This Gantt chart
is included in Appendix AB: Project Management. Each team member decided on measureable
individual milestones to track their progress. However, we underestimated the amount of time
each individual task would take. As a result, we did not make enough progress in design and
manufacturing early on to test our systems until after graduation.
H. Financial and Fund-raising
The Cedarville University engineering department provides our team with a budget to complete
some design work and fabricate and/or purchase components and parts. We focused on getting
materials donated. Our budget is included in Appendix AA: Monetary Budget.
I. Continuity and Sustainability
Team continuity remains a challenge for Cedarville’s Solar Splash teams. Because the project is
part of a capstone course, there are few underclassmen who remain involved in the project
throughout the year. The most important means of project continuity has been the shared
network drive that enables each team to access work completed by previous teams. It helps
maintain research, contacts, part specifications, reports, and test data, passing all of the
information from team to team. The end-of-the-year reports are especially useful as a summary
of work completed as well as the extensive appendices detailing specific work. This year the
team focused on creating tutorials, maintaining the networks drives to decrease clutter, and
organize our work in a concise and straight forward manner.
CONCLUSIONS AND RECOMMENDATIONS
J. Conclusions
The following discussion addresses our overall project strengths and weaknesses from this year:









1) Strengths
We reduced the overall weight of the boat by over 150 lb.
We are creating a new Solar array that will capture 20% more light at lower incoming
angles
We developed a lighter Sprint drivetrain that delivers 47% more power to the propeller
than last year’s drivetrain
We cut power losses in the Endurance motor, and battery
We developed a new data acquisition system that integrates the two control boxes for the
different events.
2) Weaknesses
Our current hydrofoil design is not predicted to lift the boat while remaining below the
allowable drag for the Endurance Event.
The manufacturing process for multiple hydrofoils takes a longer timeframe than desired.
Because we did not maintain our rigorous schedule demands, we were unable to fully test
and iterate the hydrofoils themselves and the foil articulation mechanism.
We have not quantitatively tested the Endurance drivetrain to determine if the forwardfacing pod is more efficient than the old backward-facing pod.
Solar Splash Technical Report
19
VI.CONCLUSIONS AND RECOMMENDATIONS
K. Summary of Goal Completion
Our goal is to develop a working hydrofoil system and to win the 2013 Solar Splash Challenge.
These objectives were used to set individual system goals.


A new solar array has been designed, and will be completed by competition
A hull that is lighter than what was predicted has been built, and the final attachments
will be finished this week.


We completed CFD analysis of our hull in dual phase flow. These results were validated
experimentally.
 We developed a lighter Sprint drivetrain that delivers 47% more power to the propeller
than last year’s drivetrain, and will be completed by competition
L. Where do we go from here?
Our team has made significant progress in building what is mostly a brand new boat. The solar
array and Sprint drivetrain are the two major subsystems that need to be completed.
M. Recommendations
 Future teams must continue to document and annotate their work: part design files,
analysis work, test procedures, test data, and user guides for each process. Good
documentation greatly helps future students understand the work already completed.
 At the beginning of the year, set goals that advisors think are realistic: teams may have to
underestimate what they think they can complete. Once those deadlines are in place,
resolve to follow them as closely as possible so that deadlines following will not be
delayed as well.
 Future teams should investigate new motors for the Endurance amount. This year’s team
found potential options that are smaller with equal or greater efficiency.
Solar Splash Technical Report
20
BIBLIOGRAPHY
BIBLIOGRAPHY
Bakker, A. (n.d.). Lecture 16 - Free Surface Flows. Applied Computational Fluid Dynamics. Retrieved
from http://www.bakker.org/dartmouth06/engs150/16-fsurf.pdf
Brandon, J. (2006). Reinforcing Fibers and Composites.
DeBergalis, M. (2004). Fluoropolymer films in the photovoltaic industry. Science Direct.
McCrum, N., Buckley, C. P., & Bucknall, C. B. (2006). Principles of Polymer Engineering. Oxford
University Press, USA.
(n.d.). Selecting The Right Fiber: The Lightweight, High Strength and Stiffness Solution.
(n.d.). Selecting The Right Matrix or Resin:.
Srinivasan, V., & Elyyan, M. (2013, February 12). ansys.com. Retrieved from ANSYS Fluid Dynamics
Release 14.5 Update:
http://www.ansys.com/staticassets/ANSYS/Conference/Confidence/Houston/Downloads/fluidsupdate-145.pdf
Team, 2.-2. S. (2013). End of Semester Report. Cedarville: Cedarville University.
Technology, P. (2014). powerstream.com. Retrieved from Engineering Guidelines for Designing Battery
Packs: http://www.powerstream.com/BPD.htm
Understanding R/C Brushless Motor Ratings. (n.d.). Retrieved from hotslots.com:
http://www.hotslots132.com/understanding-rc-brushless-motor-ratings-a-263.html
Solar Splash Technical Report
1
VIII. APPENDICES
APPENDICES
Solar Splash Technical Report
2
Table of Contents
APPENDICES
APPENDIX A: BATTERY DOCUMENTATION ........................................................................ 2
APPENDIX B: FLOTATION CALCULATIONS (SEE RULE 7.14.2) ........................................ 6
APPENDIX C: PROOF OF INSURANCE (SEE RULE 2.8) ........................................................ 8
APPENDIX D: TEAM ROSTER ................................................................................................... 9
APPENDIX E: OPTICS STUDY IN EXCEL .............................................................................. 10
APPENDIX F: SOLAR ARRAY ELECTRICAL CALCULATIONS ........................................ 13
APPENDIX G: MANUFACTURING THE SOLAR ARRAY .................................................... 15
APPENDIX H: MOLDING TEFLON.......................................................................................... 18
APPENDIX I: BATTERY DRAW DOWN TESTING................................................................ 19
APPENDIX J: BATTERY CHARGE TESTING......................................................................... 26
APPENDIX K: NEW MOTOR DESIGN..................................................................................... 31
APPENDIX L: ENDURANCE MOTOR TESTNG ISSUES ...................................................... 33
APPENDIX M: MOTOR LAYOUT DESIGN ITERATIONS .................................................... 34
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS .................................................. 36
APPENDIX O: SPRINT PROPELLER DESIGN ITERATIONS ............................................... 48
APPENDIX P: FEA OF HULL WITHOUT DECK ATTACHED .............................................. 53
APPENDIX Q: MECHANICAL TESTING OF HULL MATERIALS ....................................... 57
APPENDIX R: HULL MANUFACTURING TECHNIQUES .................................................... 63
APPENDIX S: FLUENT INPUT CONDITIONS ........................................................................ 75
APPENDIX T: INITIAL STRAIN GAGE TEST ........................................................................ 77
APPENDIX U: FINAL STRAIN GAGE TEST AND CHARACTERIZATION ........................ 80
APPENDIX V: OHIO SUPERCOMPUTER CENTER INSTRUCTIONS ................................. 82
APPENDIX W: OHIO SUPERCOMPUTER CENTER WEBSITE INSTRUCTIONS .............. 85
APPENDIX X: CENTER OF GRAVITY SOFTWARE.............................................................. 87
APPENDIX Y: ELECTRICAL SYSTEMS ................................................................................. 99
APPENDIX Z: POWER AND WEIGHT BUDGETS ............................................................... 107
APPENDIX AA: MONETARY BUDGET ................................................................................ 110
APPENDIX AB: PROJECT MANAGEMENT ......................................................................... 112
Solar Boat Final Report 2013-14
Appendix 1
APPENDIX A: BATTERY DOCUMENTATION
APPENDIX A: BATTERY DOCUMENTATION
This year we will be utilizing one of each battery pack that has been used in the past. A set of
three Genesis 42EP batteries weighting 32.9 lb (14.9 kg) each giving us a total weight of 98.34
lb (44.7 kg) for the first set. The second set we will use the Genesis 13EP batteries, each
weighing 10.8 lb (4.9 kg); we will use 9 of these for the second set of batteries for a total weight
of 97.2 lb (44.1 kg). This is in compliance with the new Solar Splash rule 7.4.1 having both of
the battery sets under the 100 lb (45.5kg) limit.
The specification and MSDS sheets for these two types of batteries, which were selected from
the available batteries provided by Genesis as shown in Figure Al.1, are on the following pages
in Figure A.2.
Figure A.1. Genesis 13EP and Genesis 42EP Battery Specifications
Solar Boat Final Report 2013-14
Appendix 2
APPENDIX A: BATTERY DOCUMENTATION
Figure A.2. Enersys and Odyssey MSDS Sheets (1 of 3).
Solar Boat Final Report 2013-14
Appendix 3
APPENDIX A: BATTERY DOCUMENTATION
Figure A.2 (cont.). Enersys and Odyssey MSDS Sheets (2 of 3).
Solar Boat Final Report 2013-14
Appendix 4
APPENDIX A: BATTERY DOCUMENTATION
Figure A.2 (cont.). Enersys and Odyssey MSDS Sheets (3 of 3).
Solar Boat Final Report 2013-14
Appendix 5
APPENDIX B: FLOTATION CALCULATIONS
APPENDIX B: FLOTATION CALCULATIONS (SEE RULE 7.14.2)
The surface area of the new hull which utilizes 1 layer of 1.25 inch of Nomex honeycomb is
65.0 ft2 and the surface area which utilizes 2 layers of 0.472 inches of Nomex honeycomb is
7.1 ft2 . Thus, the buoyant force provided by the hull alone, neglecting the Kevlar skins is given
by the following.
𝐵𝐻
𝑛
= (∑ 𝐴𝑖 𝑡𝑖 ) 𝜌𝑤𝑎𝑡𝑒𝑟
𝑖 =1
= (65.0 𝑓𝑡 2 ∗ 1.25 𝑖𝑛 ∗
𝑓𝑡
12 𝑖𝑛
+ 7.1 𝑓𝑡 2 ∗ 2 ∗ 0.472 𝑖𝑛 ∗
𝑓𝑡
62.4 𝑙𝑏
)
12 𝑖𝑛 𝑓𝑡 3
= 468 𝑙𝑏
Where 𝐵𝐻 is the buoyant force on the hull when submerged, 𝐴𝑖 is the surface area covered by a
given core thickness, 𝑡𝑖 is thickness of the core in a given region, and 𝜌𝑤𝑎𝑡𝑒𝑟 is the density of
water. Because the batteries are secured to the hull, their buoyant force also contributes the
overall buoyant force on the boat. The volume of 3, 42 EP batteries is less than that of 12, 13 EP
batteries, and will therefore be used for our calculations.
𝐵𝐵 = 3𝑉42𝐸𝑃 𝜌𝑤𝑎𝑡𝑒𝑟
= 3 ∗ 0.175 𝑓𝑡 3 ∗ 62.4
𝑙𝑏
𝑓𝑡 3
= 33 𝑙𝑏
Where 𝐵𝐵 is the buoyant force of the batteries and 𝑉42𝐸𝑃 is the volume of the Genesis 42EP
batteries. Therefore, the maximum possible buoyant force exerted on the hull is given by the
following.
Solar Boat Final Report 2013-14
Appendix 6
APPENDIX B: FLOTATION CALCULATIONS
𝐵𝑡𝑜𝑡
= 𝐵𝐻 + 𝐵𝐵
= 468 𝑙𝑏 + 33 𝑙𝑏
= 501 𝑙𝑏
Also, the weight of the hull, as given by the power budget is shown in Table B.1. Based on our
calculations, our new hull can easily support its own weight plus a 20% safety factor as the
buoyant force of 501 lb is much greater than the required buoyant force of 370 lb.
Table B.1. Weight Budget for 2014 Solar Splash Boat
Components
Solar Array
Batteries
Sprint Drivetrain &
Controllers
Endurance Drivetrain
Hull
MPPT
Control Panel
Miscellaneous
Weight [lb]
2014
2014 Sprint
Endurance
N/A
42
100
100
70
70
24
53
N/A
5
10
24
53
4
5
10
Total
262
308
120% Total (Rule 7.14.2)
314
370
Solar Boat Final Report 2013-14
Appendix 7
APPENDIX C: PROOF OF INSURANCE
APPENDIX C: PROOF OF INSURANCE (SEE RULE 2.8)
Solar Boat Final Report 2013-14
Appendix 8
APPENDIX E: OPTICS STUDY IN EXCEL
APPENDIX D: TEAM ROSTER
Name
Joel Dewhurst
Scott Gay
Joe Girgis
Trevor Leeds
Nik Shroeder
Degree Program
BSME
BSME
BSME
BSME
BSME
Year
Senior
Senior
Senior
Senior
Senior
Joel Ingram
Luke St.
Pierre
BSME
Senior
BSME
Senior
John Howland
BSME
BSEE and BS
Mathematics
BSEE and BS
Mathematics
Senior
Role
Solar Array Design and Manufacture
Energy Management
Endurance Motor Redesign
Sprint Drivetrain and Motor Design
Propeller Design and Manufacture
Lightweight Hull Design and
Fabrication
Lightweight Deck Design and
Manufacture
CFD analysis and Strain Gauge
Verification
Junior
Circuit and Control Systems Design
Junior
Circuit and Control Systems Design
Jacob Dubie
Jay White
Solar Boat Final Report 2013-14
Appendix 9
APPENDIX E: OPTICS STUDY IN EXCEL
APPENDIX E: OPTICS STUDY IN EXCEL
In order to determine if a surfaced top layer would increase the amount of sunlight captured by
the array we conducted an optics study. A major portion of the optics study was conducted in
Excel. The first thing we did was create a worksheet that calculated the amount of light refracted
by a surface as a function of incoming angle. We created a top layer material reference table that
allows the user to select different materials, and prism shapes for the top layer, and observe the
differences. Figure E.1 plots
refracted light for varying
incoming angles, and shows that
for the low angle conditions the
morning races will be in, a
significant amount of light is
reflected. In order to determine the
margin of improvement needed in
Amount of Light Transmitted (%)
100%
P Polarized Light
60%
Average
i
Ray
40%
20%
Brewster’s
Angle
Surface
0%
0
power produced by the new solar
array.
S Polarized Light
80%
20
40
60
Incident Angle (Degrees)
80
Figure E.1. Transmitted light as a function of incoming
angle
We analyzed the
performances of the existing Solar Splash array, and the Netherland’s array. The results are
shown in Table E.1
Table E.1. Analysis of the existing arrays performance’s
Solar Splash Array
Nominal Power
Pactual (W)
Dong SC Array
Nominal Power
Pactual (W)
# Cells
270
425
# Cells
502
1698
Pcell (W)
2.77
% Of Nominal Power
Pcell (W)
4.2
% Of Nominal Power
Ptotal (W) 747.9
56.8%
Ptotal (W) 2108.4
80.5%
These results show, that our existing arrays are drastically under-powered under the new rule
change.
We then created a worksheet to compare a surfaced top layer with a flat top layer. The user
inputs the number of prisms, the top layer material, and the angle of the prisms. The worksheet
Solar Boat Final Report 2013-14
Appendix 10
APPENDIX E: OPTICS STUDY IN EXCEL
then calculates the amount of light refracted for each top layer, as a function of incoming angle
and plots the two curves for comparison.
The Excel workbook contains five worksheets.
Comparison of Toplayers
This worksheet is a figure of plotted data for a flat top layer verses a surfaced top layer. It pulls
data from the Top Surface Comparison and the Transmission worksheets. The textbox with the
prism angle updates automatically each time that value is changed in the Top Surface
Comparison worksheet. It also displays the two mediums through which the light is traveling.
These values are also automatically updated.
Top Surface Comparison
This worksheet calculates the data points for light captured by the surfaced top layer. The top left
of the worksheet contains parameters that can be changed. The two media inputs are drop down
menus that reference the
Index of Refraction (IOR)
Table worksheet. These
Table E.2. Top surface comparison worksheet parameters
These values are parameters to be changed
These values are drop down menus
Don't change these values
parameters are shown in
Table E.2. The colors
1st Medium
Air
indicate which parameters
2nd Medium
Teflon (FEP)
1
1.34
Angle of Number of Height of
Prism (°)
Prisms
Prisims
45
50
0.060
are inputs, and which ones are outputs. The orange cells are drop down menus, based on these
the values from the IOR table appear in the
greyed out cells below. The green cells indicate
user inputs, and these values are automatically
updated in the Comparison of Top Layers
chart. Figure E.2 shows a diagram of the angles
referenced in the grey cells. These angles are
all used in determining the angle of incidence
Figure E.2. Angle Diagram
Solar Boat Final Report 2013-14
for both sides of the prisms.
Appendix 11
APPENDIX E: OPTICS STUDY IN EXCEL
Transmission
This worksheet contains the refraction calculations for a flat top layer. This worksheet has
parameters similar to the Top Surface Comparison worksheet. These parameters are the only
thing that are changed in the worksheet. The grey table calculates the numbers for plotting the
figure. This plotted data is shown in Figure E.1.
IOR Table
This worksheet contains the Index of Refraction (Refractive Index) for certain materials. These
are the materials that show up in the drop down menus on the Top Surface Comparison and
Transmission worksheets. The lists are set up so materials can simply be added onto the end of
the table.
Current Array
This worksheet shows the nominal power calculations for the 2010 built Solar Splash array, and
the 2012 built DONG Energy Solar Challenge array. These calculations are shown in Table E.1.
Solar Boat Final Report 2013-14
Appendix 12
APPENDIX G: MANUFACTURING THE SOLAR ARRAY
APPENDIX F: SOLAR ARRAY ELECTRICAL CALCULATIONS
Our solar array uses monocrystalline cells from Everbrite Solar. The solar cell specifications
provided by Everbright Solar are shown in Figure F.1.
Figure F.1. Cell Specifications for 19% efficient solar cells from Everbright Solar
Note that Vmp and Voc are mislabled. Voc should be 0.639 V, and Vmp should be 0.541 V. Using
the maximum nominal power (4.59 W) we calculated the nominal power of the solar array.
𝑃𝑎𝑟𝑟𝑎𝑦 = 𝑛𝑐𝑒𝑙𝑙𝑠 ∗ 𝑃𝑚𝑝
(F.1)
Where Pmp is the nominal peak power of a cell, ncells is the number of cells in our array, and P array
is the nominal power of the entire array. We created a spreadsheet to calculate the nominal
power of the array as well as the open circuit voltage of each series. The series open circuit
𝑉𝑝𝑎𝑛𝑒𝑙𝑜𝑐 = 𝑛𝑐𝑒𝑙𝑙𝑠 ∗ 𝑉_𝑜𝑐
(F.2)
voltage is calculated by multiplying the individual open circuit voltage by the number of cells in
a series. To be conseritive we used the high end nominal power of 4.59 W.
Solar Boat Final Report 2013-14
Appendix 13
APPENDIX G: MANUFACTURING THE SOLAR ARRAY
These power and voltage values are shown in Table F.1
Table F.1. Solar Array Voc and Pmp calculations
Solar Cells
Cell Specifications for 1000 W/m2
Everbright Solar Monocrystalline
Type
19.0
% Eff.
Impp [A]
8.45
Vmpp [V]
0.543
*Pmpp [W]
4.59
Isc [A]
8.89
Voc [V]
0.639
Panel 1
Number of Cells Per Panel
Vmpp of Panels [V]
Voc of Panels [V]
Power of Panels [W]
Total Array Power [W]
Panel 2
Panel 3
36
36
43
19.5
19.5
23.3
23.0
165.2
23.0
165.2
27.5
197.4
115
Total # of Cells
115
From the table our solar array’s nominal power is 527.9 W, and our maximum source open
voltage is 27.5 V both values are under the max allowed, 528 W mp , and 52 Voc respectively.
Solar Boat Final Report 2013-14
Appendix 14
APPENDIX G: MANUFACTURING THE SOLAR ARRAY
APPENDIX G: MANUFACTURING THE SOLAR ARRAY
For our solar array we need 115 solar cells. There are 20 individual panels, which make up three
series. Each cell requires three tabbing wires to be soldered on, so that the cells can be built up in
series to build a panel. Each of these wires are cut from a spool and crimped using a cutting and
crimping jig created by Tom Poore in 2012. Figure G.1 Illustrates this process.
1. The wire is pulled
through the cutter,a nd
3. Strike downward to cut wire.
clamped in place,
2. It is then crimmped by
2. Press wire into
corner to crimp
pressing a fingernail, or a
sharp corner against the
crimping platform.The
crimping the cells can be
1. Clamp end of wire
soldered in series.
3. The wire is then cut
4. Flux is then used on the
Figure G.1. Cutting and Crimping the Tabbing wire.
wires and the solar cell.
Figure G.2 illustrates applying flux to the soldering pads on the solar cell. The flux cleans
the surfaces allowing the solder to
flow freely. Without the flux it us
much hard to achive a good solder
joint between the tabbing wire and
the soldering pads on the solar cells.
The tabbing wire we use is pretinned
meaning no additional solder is
needed. Care must be taken to avoid
straying with the flux. Flux pens
make this task easier. A narrow band
Figure G.2. Applying flux to the solar cells
Solar Boat Final Report 2013-14
with very little flux on the cells. The
flux is hard to clean off the cells.
Appendix 15
APPENDIX G: MANUFACTURING THE SOLAR ARRAY
5.
Once the solder is applied to both the cells and the tabbing wires, the wires can then be
soldered to the cells. Figure G.3
illustrates the soldering of the
Unsoldered Tabbing Wire
tabbing wires to the cells. Solder
the wires to the light asorbing side
of the cells (the dark blue side).
Care should be made that the
direction of the crimp is in the right
orrientation, so the that the wire
once it leaves the end of the cell, is
flush with the base of the cell. This
Soldered Tabbing Wire
year the cells were soldered at
Figure G.3. Soldering the tabbing wires to the solar cells
400°C. When soldering the cells, it
should be done quickly, and without stopping. There should be a small pool of solder
around the tip of the soldering iron as it move along the tabbing wire. The tip should be
cleaned after every run, to ensure a clean and good conection. One cell in each series
need extra long tabbing wires.
6. These cells go at the end of a series of three
cells, as shown in Figure G.4, they are
Soldering tabbing wires to
the back of the next cell
folded 45° to make a 90° corner. The panels
this year are mostly 3 x 2, meaning six cells
per panel. The tabbing wire that is soldered
to the top of one cell is soldered to the
bottom of the next. Again flux is used on
Figure G.4. Soldering the cells in series
of threes
both surfaces prior to the soldering to ensure a good soldered joint.
7. Two strings of three cells, one ending with a long wired cell, and one ending with a
regular length wired cell are then soldered together to for a series of six cells. The long
wire is folded over. For the middle section the three wires are running over each other.
Solar Boat Final Report 2013-14
Appendix 16
APPENDIX G: MANUFACTURING THE SOLAR ARRAY
These are soldered together. Then as the bus reaches the other cells each wirer is folded
off in turn to be soldered to the next cell.
8. Once a series of six cells are
soldered together busbars are
added, as shown in Figure G.5.
The tabbing wire
cutting/crimping jig was
modified to crimp the busbar
Tabbing wire connection
wires. The busbar connected to
Busbars
the positive side of the series, is
crimped to go the negative
Figure G.5. Soldering the busbars to the series.
busbar on the next series.
9. The panels are then laminated. The layup from top to bottom is:

Teflon

EVA

Solar Cells

EVA

Tedlar (Polyvinyl fluoride)
The lamination is performed at 300 °f.
10. Diodes, which are shown in Figure
G.6, are added bridging the negative
and positive busbar terminals of each
panel. If the panel voltage is too low,
Anode: Connect to
the negative side
of the solar panel
Cathode: Connect
to the positive side
of the solar panel
than the diodes bypass that panel so
that it doesn’t limit the others.
Figure G.6. Smart Bypass Diode connections
Solar Boat Final Report 2013-14
Appendix 17
APPENDIX H: MOLDING TEFLON
APPENDIX H: MOLDING TEFLON
We selected Teflon as the initial choice for the surfaced top layer, due to its superior optics
properties to EVA. Teflon has a lower refractive index, and a higher transmissibility. Therefore
more light is refracted into the top layer, and more of that
light gets through. We designed a sample platen to mold
this Teflon under vacuum pressure. This platen was made
using a 45° engraving bit on the CNC. Figure H.1 shows
the platen being cut on the CNC. The prism heights are 30
thousandths. There are 51 ridges per cell. The sample
platen was cut with a low axis feed rate and a very high
Figure H.1. Sample platen being
cut on the CNC
spindle speed, to achieve a polished finish, with very little post CNC work. The melting point for
FEP Teflon is ~290°C (554°F). This temperature cannot be achieved in the oven Tom created in
2012.
We were able to successfully for Teflon. This
is a major achievement by itself. Figure H.2
shows the molded Teflon, with the prisms for
Figure H.2. Sample surfaced top layer, with
prisms fully formed.
the surfaced top layer.
We have been manufacturing samples in the small properties lab ovens. These are big enough for
a single cell. Once the process is perfected we will
begin manufacturing the entire array. We have been in
contact with the University of Dayton Research
Teflon failed to
form
Institute concerning the use of an autoclave. We
Burned EVA
investigated a one-step lamination process, but had
several issues. Figure H.3 shows the fronts and backs of
two, one step lamination attempts. The one the left side
was brought up to 300°C and kept there for 10 min. The
Figure H.3. Single step lamination
attempts, one failed to form the Teflon,
and the other burned the EVA.
Teflon didn’t reach formable temperature. The second
one, on the right, was brought up to temperature, and
held there for 20 min. This allowed the EVA to get to hot, and it burned, it is responsible for the
bubbles that can be seen on top, and the blacked bottom of the lamination.
Solar Boat Final Report 2013-14
Appendix 18
APPENDIX I: BATTERY DRAW DOWN TESTING
APPENDIX I: BATTERY DRAW DOWN TESTING
Low Current Testing
A low current draw down test was performed in order to simulate the draw down that the
batteries will be undergoing during the Endurance race. The low current battery testing was done
using a variable load bank, Figure I.1 that can vary from 1-100 Amps. The load was dissipated in
a series of 13 transistors that
burn up the current as it flows
into the transistor bank. A very
helpful feature of the test bank
is a low voltage cutoff that
stops the circuit from pulling
amps when the battery drops
below a load voltage of 8V,
Figure I.1. Low Amperage Battery Testing Circuit
this prevents damaging the
lead-acid batteries. The test data (battery voltage and current) was collected using National
Instruments Data Acquisition System (DAQ) that communicates with the LabView software of
the computer via USB.
The 42EP batteries were tested at around 18 Amps per 12V battery and the 13EP batteries were
tested at an equivalent (meaning each 3 batteries in parallel equal a 12V 42EP) that ended up
being only 15.5 Amps – 16 Amps because the batteries would not last the full 2 hours at 18
Amps. The system equivalent for the 42EP is 54 – 56 Amps in a 12V system. We will be running
the system with three 12V batteries in parallel meaning that the current draw for one battery
would be tripled to calculate the system current. The reason for this is because it is the most
convenient and advantageous to use the extra battery weight allocated to the Endurance Race this
year per Solar Splash rule 7.4.1. Since the 13EP batteries weigh less, we can use up to 9 of them
in our 12V endurance configuration that we will be using this year. Taking a system amperage of
about 54 Amps and dividing by the 9 batteries gives an amperage of 6 Amps per 13EP.
However, testing at the amperage as low as 6 Amps gave some questionable current readings on
the DAQ. Part of this reason was due to the size of the shunt being used. The shunt was large
enough and was only sending very small voltages to the National Instruments, leaving room for
Solar Boat Final Report 2013-14
Appendix 19
APPENDIX I: BATTERY DRAW DOWN TESTING
the tiniest offset to throw off the readings. This problems prompted us to test the 13EP batteries
in sets of 3 which raised the test amperage to about 18Amps. Raising the amperage by three
times provided a better signal for the DAQ to interpret.
High Current Testing
The High Current testing is done on a much more robust set
of resistors that can handle upwards of 1500 Amps. In order to
dissipate the current that is being drawn from the batteries
large resistors (0.157 Ohm and 0.069 Ohms are used in
series or parallel) are used. The configuration of these
resistors is the way that the load bank becomes
variable. For a different desired load, the system
resistance is changed, by rearranging the resistors, to
draw current from the batteries. The load bank is
pictured here in Figure I.2. To calculate the
Figure I.2. High Current Load Bank
configuration for a desired load we used an optimization function in Excel that output the
resistors in series and/or parallel to use in order to give a desired current. We set up an equation
that takes into account the number of 0.157 and/or 0.069 Ohm resistors in series, as well as the
number in parallel. Equations I.1 below calculates the load that we will need for the desired
current. It is shown in the column titled “Necessary Load” in Table I.1.
𝑉
𝑁𝑒𝑐𝑒𝑠𝑠𝑎𝑟𝑦 𝐿𝑜𝑎𝑑 (Ω) = ( 𝑏𝑎𝑡𝑡 ) − 𝑅𝑏𝑎𝑡𝑡
𝐼𝐿𝑜𝑎𝑑
(I.1)
12 𝑉
𝑁𝑒𝑐𝑒𝑠𝑠𝑎𝑟𝑦 𝐿𝑜𝑎𝑑 (Ω) = (
) − 0.0045 𝐴
100 𝐴
(I.2)
𝑁𝑒𝑐𝑒𝑠𝑠𝑎𝑟𝑦 𝐿𝑜𝑎𝑑 (Ω) = 0.116 Ω
(I.3)
The above equations show what load is necessary to pull 100 Amps from a 12 V source. The
next Equation is what Excel uses to optimize the calculated load to match the desired load of
0.116 Ω.
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Appendix 20
APPENDIX I: BATTERY DRAW DOWN TESTING
𝐴𝑐𝑡𝑢𝑎𝑙 𝐿𝑜𝑎𝑑 = (𝑁𝑆_0.069 ∗ 0.069 Ω) + (𝑁𝑆_0.157 ∗ 0.157 Ω)
(I.4)
+ (1/((𝑁𝑃_0.069/0.069Ω) + (𝑁𝑃_0.157/0.157 Ω)))
The variables NS and NP represent the amount of resistors that will used in the configuration.
NS representing the number of resistors in series and NP representing the number of resistors in
parallel. Since we only have 6 of each resistor, neither of those numbers can be larger than 6. As
soon as all the parameters were set Excel optimized the equation trying to get close to the
Necessary Load for each desired current. As seen in Table I.1, for a load that uses one 0.069 Ω
Resistor in parallel with one 0.157 Ω resistor in series with one 0.069 Ω resistor gives a total
load of 0.117 Ω. For the example of 100 Amps of current this is very close and using I.1 – I.3 the
actual current draw will be 98.8 Amps. This is very close to the 100 Amps and will accurately
represent the data that is desired to learn. This same process was carried out for each desired load
and the results can be seen in Table I.1 for the 42EP test and in Table I.2 for the 13EP test. Each
battery type needed its own calculation because of the difference in internal resistance.
Table I.1. Examples of High Current Resistor Configuration for a Desired Load
Resistor Configurations for High Amperage Testing (42EP)
Desired Current
900 A
# of 0.069 in parallel
3
# of 0.157 in parallel
0
1000 A
# of 0.069 in parallel
3
# of 0.157 in parallel
1
1400 A
# of 0.069 in parallel
5
# of 0.157 in parallel
1
1500 A
# of 0.069 in parallel
6
# of 0.157 in parallel
0
Necessary Load
0.022 W
# of 0.069 in series
# of 0.157 in series
0.020 W
# of 0.069 in series
# of 0.157 in series
0.013 W
# of 0.069 in series
# of 0.157 in series
0.012 W
# of 0.069 in series
# of 0.157 in series
Solar Boat Final Report 2013-14
Actual
Load (W)
0.023
Actual
Current
Current (A) Difference (A)
872.7
27.3
1/22/2014
Voltage
(V)
24
0
0
0.020
977.2
22.8
24
0.013
1396.6
3.4
24
0.012
1500.0
0.0
24
0
0
0
0
0
0
Appendix 21
APPENDIX I: BATTERY DRAW DOWN TESTING
Table I.2. Resistor Configuration for High Amperage Testing (13EP)
Resistor Configurations for High Amperage Testing (13EP)
Desired Current
800 A
# of 0.069 in parallel
3
# of 0.157 in parallel
0
900 A
# of 0.069 in parallel
3
# of 0.157 in parallel
2
1300 A
# of 0.069 in parallel
5
# of 0.157 in parallel
4
1400 A
# of 0.069 in parallel
6
# of 0.157 in parallel
4
Necessary Load
0.007 W
# of 0.069 in series
# of 0.157 in series
0.005 W
# of 0.069 in series
# of 0.157 in series
0.010 W
# of 0.069 in series
# of 0.157 in series
0.009 W
# of 0.069 in series
# of 0.157 in series
Actual
Load (W)
0.023
Actual
Current
Current (A) Difference (A)
774.2
25.8
11/6/2013
Voltage
(V)
12
0
0
0.018
930.7
30.7
12
0.010
1317.9
17.9
24
0.009
1420.6
20.6
24
0
0
0
0
0
0
After all the resistors were calculated the test set up could be completed with the DAQ and other
signal recording components. The final circuit diagram for the test setup can be seen below in
Figure I.3.
Figure I.3. High Current Test Circuit Diagram
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Appendix 22
APPENDIX I: BATTERY DRAW DOWN TESTING
Testing Results
A typical curve for a battery draw down test was shown earlier to briefly describe what happens
to each measured value over the course of the test. Figure I.4 is a more detailed look at a 2 hour
draw down test done at an average of 18.4 Amps. Table I.3 shows a brief summary of the test.
Figure I.4. Battery 2014-4 Low Current Discharge Test (18.4A Avg)
The pattern that these curves follow is typical
for each parameter that they are tracking. The
current stays almost constant due to the nature
of the constant load bank that is used to draw
current. The voltage and power follow the
same trend of course, because power is simply
Table I.3: Draw Down Test Summary
Avg Current
Voltage @ 2hr
Amp-Hr
Power @ 2hr
Energy (kJ)
Energy (W-Hr) @2hr
18.40 Amps
10.80 Volts
35.83 Amp-Hr
591.46 Watts
4650.24 Kilo Joules
1396 W-Hr
the product of voltage and current. The energy of the system, whether denoted by W-Hr or
Joules, increases over time as it represents the integral of the power. During the discharge
testing, the voltage is of particular interest. It is obvious to see that right around 10V the voltage
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Appendix 23
APPENDIX I: BATTERY DRAW DOWN TESTING
starts to drop off drastically. It is critical for us to understand the voltage at the end of a 2 hour
draw down test for each battery to ensure that they do not get to far past the 10V mark at 2 hours.
If it does we do not want to use that battery for a race. The problem with running the batteries
that close to the drop off point is not only the fact that there will not be any power to run the
propeller but also the fact that when lead-acid batteries are run down that low it may cause
permanent damage to them.
The most important part of the testing results is the practical things that they are able to tell us. In
this case we were exploring the advantages and disadvantages of using the 42EP for Sprint and
the 13EP for Endurance (the opposite of what they are normally used for). For the Endurance
testing we used the averages of a few similar test runs in order to compare the 13Ep and the
42EP. Tables I.4 and I.5 show the summarized data for the 42EP and the 13EP batteries
respectively. After we calculated the averages for the testing data. It was possible to begin to
Table I.4. 42 EP Test Averages
42
Avg Current (A) System Current (A) Voltage @ 2hr (V) Power @ 2hr (W) Energy Output (J) Amp/Hr @ 2 hr
2014-2
18.57
55.72
10.13
569.69
4651.52
35.89
2014-4
18.40
55.19
10.80
591.46
4650.24
35.83
2014-24
18.26
54.78
10.88
600.83
4574.87
35.30
2014-25
18.23
54.68
10.90
610.50
4594.67
35.45
Average
18.36
55.09
10.68
593.12
4617.83
35.62
Table I.5. 13EP Test Averages
13
Avg Current (A) System Current (A) Voltage @ 2hr (V) Power @ 2hr (W) Energy Output (J) Amp/Hr @ 2 hr
2014-6,7,8
16.09
48.26
10.25
492.40
4100.39
31.60
2014-12,13,14
15.48
46.43
10.30
482.89
3882.21
29.96
Average
15.78
47.34
10.27
487.64
3991.30
30.78
analyze how the difference in power would actually effect our performance at competition. By
taking the percent difference in Energy, for our data it was 13.57%, it is possible to relate this to
the velocity of the boat during the race. Velocity is proportional to the square root of the energy.
Therefore by following the equation shown we can know about how many points we will lose
operating with lower energy. The calculations are done using the premise that the 42EP tested
this year will win the Endurance portion of the competition and earn us the full 400 points. Last
year the team completed just over 40 laps, an average of about 10 points per lap.
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Appendix 24
APPENDIX I: BATTERY DRAW DOWN TESTING
𝐿𝑎𝑝𝑠 𝑤𝑖𝑡ℎ 13𝐸𝑃 = (√(1 − .1357)) ∗ 40
(I.5)
Laps with 13EP = 37.188
(I.6)
Points with 13EP =37.188*10
(I.7)
From I.7 we can see that the total amount of points that we would get from the 13EP is about 372
points. This is a 28 point (7%) reduction from 400 points. These same principals can be carried
over to the Sprint race to figure out how well the 13EP outperform the 42EP. Table I.6 shows the
test results for each of the 13EP and the 42EP. Once again we will be using the 13EP data as if it
was the data
Table I.6. High Current Test Results after 25 Seconds
13EP
42EP
Current (A)
1075.20
1044.12
Voltage (V)
24.92
18.14
Percent Difference
Power (W)
26796
18935
29.34
Energy (J)
743329
558679
24.84
when the 13EP
won the 300
meter Sprint
race in 26.06
seconds. The 42EP battery energy would only allow the boat to travel 260 meters in 26.06
seconds. The speed of the boat for this to happen would be 9.98 m/s. If the boat is traveling at
9.98 m/s it would take 30.06 seconds to go the necessary 300 meters. According to the Solar
Splash point calculations:
𝑆𝑐𝑜𝑟𝑒 =
𝑊𝑖𝑛𝑛𝑖𝑛𝑔 𝑇𝑖𝑚𝑒 (26.06)
∗ 250
𝑌𝑜𝑢𝑟 𝑡𝑖𝑚𝑒 (30.06)
(I.8)
From this the score that the 42EP batteries would get is about 216 points as opposed to the 13EP
which would provide the win, earning the maximum 250 points. The Sprint race point
differential is 34 points (13.6%). Based on these results it seems as if having one pack of each at
competition will be beneficial so that in the most crucial times we can perform at the boat’s best
ability depending on the race we are competing in. Some might think that it would be worth
throwing away the 7% loss in endurance and be able to run the endurance race at full capacity
each time. It seems like that could be a choice but the thought is that with effective batter-tobattery charging we will have enough total energy that we can charge the pack efficiently to
perform well in each race no matter what sequence of races we need to run in a given day.
Solar Boat Final Report 2013-14
Appendix 25
APPENDIX J: BATTERY CHARGE TESTING
APPENDIX J: BATTERY CHARGE TESTING
Wall Charger Test
In addition to understanding the life of the batteries under the load that we expect them to be
experiencing, it is also important to understand the charging of the batteries. In an attempt to
learn how much energy it took to fully charge the batteries we recorded the battery voltage and
current that the wall charger put into a dead battery. We are defining a dead battery as one that
has undergone a simulated endurance
Wall Charger
Laptop
draw down test. The test setup
that was used can be seen in
Current Shunt
Figure J.1. A current shunt is used to
measure the current that is being put
into the batteries. The national
National Instruments
instruments is the device that talks to
the Labview Recording Software on
Figure J.1. Wall Charger, Charging Test Setup
the laptop via USB. The circuit
diagram for the setup is shown below in Figure J.2. The circuit diagrams are helpful in order to
double check the wiring to ensure that nothing is being shorted out. This becomes particularly
important during the solar panel charging test because shorting things out could damage
components or cause damage to the batteries.
The battery wall charging did not yield favorable results. The charger is designed in order to
pulse on and off and to check the battery voltage and then determine the amount of current that it
should be putting into the battery.
It seems that this would be
relatively simple to interpret the
data but the current in not constant
that is being put into the battery
and therefore the amount of
energy being put in cannot be
Figure J.2. Wall Charging Test Circuit Diagram
accurately calculated using the
pulsing current data. A full charge of a battery is seen below in Figure J.3 and shows how the
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Appendix 26
APPENDIX J: BATTERY CHARGE TESTING
Float Charge
Full Charge
Full Charge
Figure J.3. Wall Charger Test, Full Charge Cycle
Voltage increases over time and it also shows an obvious point at the end of the charge where the
charger determines the battery is full and goes into “float” charge mode. Float charge mode is
when the charger maintains a certain voltage (about 13.4 V for a 12 V battery) in order to not
overcharge and damage the batteries.
It is very hard to see what is going on with the current when only looking at the whole test, so
Figure J.4 just below the full test shows minutes 1-10 of the charge. In this figure it is easy to see
that the charger is putting current in and then waiting to read the battery voltage and then pulsing
again to fill the battery. This process is continued over the whole charging cycle. Since the data
gathered from this test was not very helpful in determining the energy put into the batteries
during charging it was necessary to move onto a different solution.
Solar Charging
The next step was to use the existing solar array and outback PPT to charge the batteries with the
solar power and hopefuly get a more constant current output out of the PPT than from the wall
charger. The current was measured using the same current shunt that was used during the wall
charger testing, however the currents were not very high and the test would not yield quanifiable
results. We tried to fix the problem by adding an opAmp to the signal before it went into the
DAQ but the OpAmp had an offset and did not help to clean up the signal. After struggling to
decifer the issue with the current signal from the shunt, it was decided that we should move onto
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Appendix 27
APPENDIX J: BATTERY CHARGE TESTING
Figure J.4. Wall Charger Test, Minutes 1-10
exploring the system that we will using for competition. This included extensive knowledge of
the Morningstar SunSaver MPPT. The SunSaver is much more user friendly and programmable
when it comes to making the system do exactly what we want it to. The morningstar devices
seem to be what we need to do controlled battery-to-battery charging. We are currently in contact
with a technical expert at Morningstar and are hoping to hear back from him on how we should
preceed to allow the
devices to maximize our
performance.
One of the clever ways
that we are going to
control the SunSaver is to
use the Remote
Temperature Sensor
(RTS) on the MPPT. By
giving a voltage signal to
the RTS we can tell the
PPT that the temperature
Figure J.5. RTS Calibration Trendlines
of the batteries is anywhere from -30 to 80 degrees celsius. The PPT will then respond by giving
Solar Boat Final Report 2013-14
Appendix 28
APPENDIX J: BATTERY CHARGE TESTING
more current or less current. It does this because the properties of the lead-acid batteries. If the
batteries are cold (RTS voltage around 3.5 V) the PPT will know that to get any charge into the
batteries it must increase the current. The same goes for telling the RTS that it is hot (RTS
voltage above 0.5 V). The voltage range of the RTS was found by using a thermo couple and
measuring the voltage across the RTS at varying temperatures. The data gathered from the RTS
calibration and the corresponding trendline that fits the data is seen in Figure J.5 along with the
slope of the line.
Based on the linear fit between the temperature and voltage we know what voltage across the
RTS corresponds to a very wide range of temperatures. This allows us to have a wide range of
control over the current output of the MPPT. If we find that at the slope of -40mV/C is not
enough to hit the temperature control range that we need it is possible to go into the MS view
software and change the slope of the line to get more control over the output for the same voltage
input range. After learning how to program the MPPT and knowing the relationship between the
PPT output and the RTS voltage it was possible to complete the test setup for Solar Panel
charging using
the SunSaver
MPPT instead of
the Outback. The
circuit diagram
that we used is
shown below in
Figure J.6.
The potentiometer
in the Circuit
above is what we
are using to vary
the voltage to the
Figure J.6. SunSaver MPPT Solar Charging Circuit
RTS changing the
output current of
the SunSaver. The resistor values were chosen based on the voltage range gathered from the RTS
Solar Boat Final Report 2013-14
Appendix 29
APPENDIX J: BATTERY CHARGE TESTING
calibration testing that was mentioned above. The value of this test is to become familiar with the
SunSaver MPPT and to find out how much energy is actually going into the batteries. The next
stage will be to use the SunSaver to do battery-to-battery charging. This is on hold right now as
we await some answers from Morningstar technical support.
Solar Boat Final Report 2013-14
Appendix 30
APPENDIX K: NEW MOTOR DESIGN
APPENDIX K: NEW MOTOR DESIGN
Figure K.4. New Sleeve Design
This is the aluminum sleeve that will hold the stator instead of the welds. This reduces the hysteresis
losses in the stator, and gets rid of the thicker end laminations completely which reduces eddy current
losses.
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Appendix 31
APPENDIX K: NEW MOTOR DESIGN
Drive End
Non-Drive End
Figure K.5. Revised End Bell designs
We took our existing end bells and shaved them down since they didn’t need to be as long. The old end
bells had to be longer because they provide a space for the end turns of the motor. Now the end turns are
in the sleeve.
Solar Boat Final Report 2013-14
Appendix 32
APPENDIX L: ENDURANCE MOTOR TESTING
APPENDIX L: ENDURANCE MOTOR TESTNG ISSUES
In order to get useful results from our testing of the endurance motor we needed to gather data from two
different sources. As referenced in the main report the power into the motor was recorded from our
National Instruments DAQ, and the power out of the motor was recorded by the Magtrol Dynamometer.
An issue that arises with this matching the data points with the two sets. A clever way was discovered
when attempting to collected data from the National Instruments DAQ it was noticed that the data file
contained the exact time when we began to record data. The idea came about to synchronize the clocks on
both computers, therefore we record the time when we began collecting data from the National
Instruments and the time at which the computer began to record the dyno. Since we know what time each
computer began to record data we were then able to find a time that matches between the two of them.
Another problem that was confronted was testing without the gear box on the motor. Without the gear box
there is less friction and windage in the motor causing the rotor to continue rotating even after power is no
longer supplied to the motor. This results in a back EMF which sends electricity back to the circuitry.
Normally when the gear box is on there was enough friction to slow the rotor down fast enough that the
back EMF was negligible. However, without it the motor sent a back EMF with enough voltage to cause
the controller to overload and shut off, requiring to restart the whole system every time we tried to slow
down the motor. To solve this problem Dr. Brown provided us with a resistor bank that was connected
between the positive and negative terminals of the battery to absorb the EMF from the motor.
A third problem that stemmed from testing is the transferring of torque from the motor to the dyno. The
previous years had done a good job of creating a test apparatus for the motor to be mounted onto the dyno
and they also developed a couplers that are responsible for transferring torque from the motor to the dyno.
However a major flaw with the couplers is a lack of having multiple ways to transfer torque. The two
shafts as of now have been held by one set screw on each shaft. Which means that all the responsibility of
grabbing onto the shaft and transferring the torque falls on two set screws. Unfortunately this lead to a
damaged key way on the existing endurance motor. The set screw dug into the side wall of the key way.
To eliminate this problem a new coupler has been developed that integrates the set screw design of
previous years, as well as a clamp which should help transfer the torque.
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Appendix 33
APPENDIX M: MOTOR LAYOUT DESIGN ITERATIONS
APPENDIX M: MOTOR LAYOUT DESIGN ITERATIONS
Figure M.1. Preliminary design of a single motor
system using a TP100 motor from Fine Design RC.
The design was discarded due to the high speeds
(18,000 rpm) of the motor. There were no viable
transmission options for these speeds.
Figure M.2. Secondary design uses four 2220-12
motors and four P62 gear boxes by Neu Motors.
The design mimics the four motor design from
years previous. The design was discarded due to
the high speeds (30,000 rpm) of the motor,
maintenance required for the gear boxes, bulky
design, inability to use belt drive at the speeds of
these motors, and expense (many parts).
Figure M.3. The third design uses four 2220-12
motors, however eliminates two gear boxes. The
design was discarded due to the high speeds
(30,000 rpm) of the motor, maintenance required for
the gear boxes, difficulty in disassembly, bulky
design, inability to use belt drive at the speeds of
these motors, and expense.
Solar Boat Final Report 2013-14
Appendix 34
APPENDIX M: MOTOR LAYOUT DESIGN ITERATIONS
Figure M.4. The fourth design uses
four 4430 motors made by Neu
Motors. The design was attempted to
avoid high speed motors, and high
radial loads. The design was
discarded due to the size of the
assembly, maintenance required for
the planetary gear box, bulky
Figure M.5. The fifth design uses four 4430 motors on a
common shaft. The design was attempted to remove the
need for a transmission and to be run direct drive. The
design was modified to reduce required parts (bearings,
intermediary mounting plates), and to simplify the design
down to a concept of a four-in-one motor. This was the
final step in the process of motor layout design as far as
deciding on the concept of four motors on a common
shaft. It would have required 5 bearings (between each
motor, and a permanent enclosure to hold each motor
rigid.
Solar Boat Final Report 2013-14
Appendix 35
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
Complete Design Assembly: The completed assembly was designed after the motor had
been completely designed. Below in Figure N.1, shows the entire model and labels. The entire
motor model can be seen in an exploded view in Figure N.2.
Exa mple Bus Bar Linkage
Steering Atta chment
Control ler Box
Steering Shaft
Jeti Spin Pro 300 Controller
Motor Pod
Tra ns ition Pi ece
Figure N.1. Complete 2014 motor assembly showing existing lower gear unit (LGU), boat hull, and
transom mount.
Top End Bell
Centeri ng Ring
Wa ter Ja cket
Rotor As sembly
Sta tor Housing
Centeri ng Ring
Bottom End Bell
Figure N.2. Complete motor exploded view
Solar Boat Final Report 2013-14
Appendix 36
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
Motor End Bell: The end bell of the motor houses the bearings and holds that shaft
centered in the stators. The end bell will also serve as a mounting surface for the motor. The part
was designed in Solid Works and assembled along with all the other motor parts to verify the fit
and location of all holes. CAMWorks was then used to post process the g-code for the CNC to
manufacture the part. We then manufactured a test end bell from MDF particle board to verify
the g-code produced a good part, and to correct any potential program/machining errors. The
MDF test piece and the completed end bell can be seen below in Figure N.3.
Figure N.3. CNC milled motor end bell test model (left) and completed aluminum part (right).
CAMWorks: To learn to run CAMWorks, read through the instruction/tutorial page
offered online. This was mainly helpful in learning how to set up specific roughing, contour, or
face cuts to create the geometry of the part. From help found from other teammates that had prior
experience with the program, and the brute force method of learning (although only
recommended if familiar with machining, CNCing, and G-code), one can relatively easily guide
themselves through the process.
1. The “Stock Manager” is used to define the geometry of the material stock that the part
will be machined from.
2. A “Mill Part Setup” must be created, and an origin defined. Be careful to wisely choose
the origin for this may affect you if you must flip the part mid cycle to machine the other
side.
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Appendix 37
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
3. Once the origin is defined and the stock was defined. Right click on Mill Part Set-up in
the tree of options on the left. Select “Insert a 2.5 Axis Mill Operations,” and choose
what type of cut you would like to create.
4. In the CAMWorks operation tree that appears on the left, select the “Insert 2.5 Axis
Feature” icon and then select the curves or geometry on the part that you wish to follow
or remove within.
5. Select what finish you desire and again check to insure the first drop down arrow
confirms it is going to make the type of milling operation you desire.
6. Then click “Next” verify overall depth of cut type of finish, and then click “Finish.”
7. These steps can be repeated until all geometry is imitated by milling operations. However
it may prove wise to click the red “X” at the top left of the CAMWorks Operation Tree
on the left. There should be a hot pink milling operation under the mill part set-up you
are currently working under. If it is not there click on the “CW” tab at the top of the
Operation Tree on the left to bring you to the features tree. The feature you created
should be there. This is also an area to create 2.5 milling operations on geometry it
already recognizes.
8. Right click this operation and choose “Edit Definition.” At this point you will choose a
tool from the tool crib and define the dimensions of the cutter. Be sure to limit number of
tools you use because CAMWorks will default to some tool it believes will work from its
default tool lists.
9. In the tab labeled F/S be sure to check proper speeds and feeds for the type of material
you are cutting and the size cutter you are using.
10. For changing the speeds and feeds manually for the tool selected click the “Defined by”
drop down and select “Operation”. We typically chose 1500 rpm (for carbide tools)
which can be increased by 150% manually while the CNC is operating. We would
typically choose 0.004” cut per tooth for aluminum WITH NO COOLANT (and 0.02”
per tooth for MDF test pieces although these speeds and feeds can change greatly and
machine just fine). If coolant is desired the speed and feed can be increased, be sure to
read literature on what would be appropriate for the size cutter you are using and the
material you are cutting.
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Appendix 38
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
11. Also be sure to set the Z direction feed rate to something appropriate for what type of cut
you are doing. If you are drilling or have the end mill set to plunge, CAMWorks defaults
to 950 in/min (this is extremely fast!) change this to something around 2.5 in/min to be
safe.
12. If you are creating a roughing operation you can go to the “Roughing” tab and click the
drop down arrow for what type of pattern of cut you want it to make when pocketing out
your feature. Be careful if you choose plunge a roughing cutter might be required
depending on the step size you choose.
13. To set the step size be sure to unselect the blue percent sign boxes and for a nice finish
you want to select small step sizes with a small final cut depth if the face you are milling
to is important to have a smooth finish. For aluminum we chose a “First cut amt.” and
“Max cut amt.” of 0.02” (again with no coolant  this changes with the use of coolant)
and a “Final cut amount” of 0.005-0.01.”
14. One of the issues that we ran into of the sprint end bell and the propeller is not changing
the “X-Y Allowance” under the “Roughing” tab. If this is left default, it will leave 0.01”
of material on all sides of the cut (This is because it is a roughing cut and that is what this
operation is for). This value can manually be changed to 0.0” so that the cutter will go to
the exact dimension you specify.
15. Next select the “Feature Options” tab and choose a “Method” of entry to use stepping
down to make the next cut. We typically chose “spiral” so that the flat bottom end mill
would make the cut more easily.
16. The final step is to go to the “NC” tab. Set each of the drop down options on the left to
“Top of Stock” and change the heights to some dimension that will clearly be above the
part and any clamping that may be used. The “rapid plane” is the height the spindle must
come to before the machine is allowed to do any rapid maneuvering. The “clearance
plane” is the plane the spindle will move up to before moving to a similar operation under
the same command (such as another hole location when multiple holes are selected to be
drilled with the same tool in the same step).
17. After this you can close out of the “Edit Definition” Options and right click the milling
operation you created again and click “Generate Toolpath.”
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Appendix 39
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
18. You can preview your program at any time by clicking “Simulate Toolpath” at the top
under the “CAMWorks 2013 or CAMWorks 2013-WorkFlow tabs”. There are many
options to vary and depending on your experience with CAMWorks you can limit how
long your program will run to create your part.
19. If you are using clamps to hold your stock to the table and will have features close to
those clamps it is wise to insert a “Avoid/contain area” by right clicking the milling
operation you created under the appropriate “Mill Part Setup.”
20. To post process your program you need to upload the “HURCO files.” To do this you
must right click and “Edit Definition” of the “Mill” and go under the “Post Processor”
tab.
21. Browse for the HURCO file under the 2013-2014 Solar Boat Competition Teams (T:)
drive. Once this is uploaded you can click okay and the “Post Process” button at the top
of the toolbar should now be illuminated.
22. Click this. Choose where you want the file to be saved and then press the play button.
Once it is done open up the .txt file. Change all of the tool changes from just T?? to M06
T??. This will stop the program at a tool change and ask you to switch tools on the
machine.
23. Also at the end of any tool operation the default of CAMWorks is to rapid to z=0. This is
a major problem if your z=0 is the table of the CNC! If your part is in the way, it will
plunge through it like it wasn’t even there. Change the G28 Z0. to some value much
higher than your part, such as G28 Z6
Rotor Shaft: Due to the required accuracy and larger machine turn out requirements for
the rotor shaft of the motor, the rotor shaft was outsourced to be machined. The shaft tube was
machined with shoulders in each end and the shaft hubs were machined to be oversized. This is
because when the shaft end hubs were to be welded in place there was to be expected distortion
of the shaft tube and hubs from the heat. This would cause the shaft to be out of “trueness.” Once
the shaft end hubs were welded the entire shaft was placed back on the CNC lathe and trued up
to the required specifications. The Solid Works assembly model can be seen below in Figure
N.4, as well as the received shaft with the aluminum rotor magnet spacers in Figure N.5.
Solar Boat Final Report 2013-14
Appendix 40
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
Bearing
Washer
Non-Drive End Hub
Shaft
Drive End Hub
Magnetics Assembly
Magnets
Back Iron
Magnetics Spacer
Washer
Bearing
Figure N.4. Modeled rotor shaft assembly
Figure N.5. Manufactured rotor shaft by Alexander’s Welding and Machine, Inc.
Stator Chilling Water Jackets: The stator motor housings were manufactured from an
aluminum sheet that was sheared to size and then milled to create the tabs for peening the water
jacket in place. The first water jacket was made as a tempelate seen in Figure N.6, and then the
four jackets were machined behind it. They were then rolled to the appropriate diameter which is
seen in Figure N.7, and then the flanges were formed on a vice. The water jackets can be seen
below in Figure N.8.
Solar Boat Final Report 2013-14
Appendix 41
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
Tabs
Water Jacket
Figure N.6. Tabs for water jacket template being milled.
Figure N.7. Water jackets being roll formed to 6” diameter
Solar Boat Final Report 2013-14
Appendix 42
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
Figure N.8. Completed water jackets
Centering Rings: The centering rings are necessary to center the rotor shaft in the center
of the stators, these minimize any possible radial magnetic force misaligning the shaft so that the
motor end bells can be bolted to the motor assembly on either side. The centering rings were
modeled on Solid Works, which is seen below in Figure N.9, and CAMWorks was used to
generate the g-code for the holes to be drilled and counter bored on the face of the ring. The
diameters were all turned on the lathe from 6” stock, and then placed on the fixture, seen below
in Figure N.10, for CNCing the holes. The fixture has a 4.4” lip (Inside diameter of the centering
rings) around the center axis for holding the rings concentric to the X and Y zero of the part. The
1” bore in the center of the fixture is for a 1” round bar, that will be inserted into the CNC
spindle, that will locate the X and Y zero of the fixture.
Solar Boat Final Report 2013-14
Appendix 43
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
Figure N.9. Centering ring for drive end side of motor
Figure N.10. Centering ring fixture
Solar Boat Final Report 2013-14
Appendix 44
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
Various Parts: The shaft washers, seen in Figure N.11, are to space the distance between
the step down of the shaft and the bearings. These were turned from UHMW polyethelene on the
lathe.
Figure N.11. UHMW PE rotor shaft bearing spacers
The shaft coupler was turned on the lathe and then further machined on the mill. The tapped
holes as well as the square shaft hole were machined using a v-block for support of the work
piece, alignment, and accuracy for hole centers. The shaft coupler, seen in Figure N.12, has a
welded rod in the center to restrict one shaft pushing out the other shaft from the coupler (which
has been an issue in years past.
Figure N.12. Square shaft rigid coupler
Solar Boat Final Report 2013-14
Appendix 45
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
Water Jacket fittings were needed for (1) screwing the two flanges together, and (2) adding
material for threading the NPT for the brass fittings for the water lines. These fittings can be seen
below in Figure N.13. Both of these parts were machined from aluminum on the mill.
Figure N.13. Water jacket fittings
A water distributor, seen below in Figure N.14, was machined for distributing the water from
either a pump or a pick up line under water to four inlet lines to the water jackets. This piece was
machined from aluminum on 20˚ blocks, seen below in Figure N.15. A stop was used on the vice
to hold the angled blocks in position, and the block was rotated 90˚ each time to split the inlet
into the four separate lines. The block was then machined down on the lathe, seen below in
Figure N.16.
Figure N.14. Aluminum water distributor to split inlet water lines to the four water jackets
Solar Boat Final Report 2013-14
Appendix 46
APPENDIX N: FINAL SPRINT MOTOR DESIGN & PARTS
Figure N.15. Drilling the water distributor holes at 20˚ on mill
Figure N.16. Turning the water distributor down from the block stock.
Solar Boat Final Report 2013-14
Appendix 47
APPENDIX O: SPRINT PROPELLER DESIGN ITERATIONS
APPENDIX O: SPRINT PROPELLER DESIGN ITERATIONS
Figure O.1, illustrates the first alternate design considered.
Figure O.1. Converged design consideration for 4-blade propeller, and performance curves
This propeller’s performance characteristics can be seen in Table O.1
Table O.1. Design Characteristics of 4-blade propeller consideration in Figure O.1
# of Blades
4
Efficiency
69%
Diameter
7.92 inches (0.2 m)
Thrust Produced
265 lb (1179 N)
Torque
38.6 ft-lb (52.3 N-m)
Operating RPM
5000 RPM (523.6 rad/sec)
Boat Speed
36 mph (57.9 kph)
Power Required
36.7 hp (27.3 kW)
I stopped trying to make this design work due to the following reasons.

The propeller is cavitating.
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Appendix 48
APPENDIX O: SPRINT PROPELLER DESIGN ITERATIONS

The performance curves show that the propeller is far less efficient than what the power
budget is designed around.

The propeller profile would not be able to be machined on our CNC mill
As can be seen from Figure O.1, the blade areas of each of the individual blades are starting to
overlap. Normally this would not be a problem, except the CNC that we have access to does not
have the ability to machine 5 axes. Thus we began to consider an alternate design.
My second design consideration is intended to eliminate the need for overlapping blade area.
Thus we started designing 3-blade propellers using the most recent power budget’s inputs. This
iteration led me to design the propeller in Figure O.2.
Figure O.2. 1st 3-Blade design consideration showing blade profile and performance curves
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Appendix 49
APPENDIX O: SPRINT PROPELLER DESIGN ITERATIONS
Table O.2. 1st 3-Blade propeller design operating characteristics
# of Blades
3
Efficiency
70%
Diameter
7.36 inches (0.187 m)
Thrust Produced
265 lb (1179 N)
Torque
38.6 ft-lb (50.7 N-m)
Operating RPM
5000 RPM (523.6 rad/sec)
Boat Speed
36 mph (57.9 kph)
Power Required
35.6 hp (26.5 kW)
Figure O.2 shows us that the propeller does not have any overlapping blade area, and Table O.2
shows the performance of the propeller will be about 70% efficient. These parameters may not
satisfy the machinability requirements of the CNC. The propeller is not drawing the right amount
of power. Since there is additional power available, another design that will utilize this power
will be required. The next design illustrated in Figure O.3 is intended to increase the ease of the
machinability, utilize the power available and increase the efficiency of the propeller.
Figure O.3. 2nd 3-Blade design consideration intended to increase efficiency and ease
machinability.
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Appendix 50
APPENDIX O: SPRINT PROPELLER DESIGN ITERATIONS
Table O.3. 2nd 3-Blade design operating characteristics
# of Blades
3
Efficiency
72%
Diameter
7.32 inches (0.186 m)
Thrust Produced
258.5 lb (1150 N)
Torque
38 ft-lb (51.5 N-m)
Operating RPM
5000 RPM (523.6 rad/sec)
Boat Speed
38 mph (61.2 kph)
Power Required
36.2 hp (27.0 kW)
The propeller in Figure O.3 does have increased efficiency as seen in Table O.3, and is
theoretically machinable, however, the blades are very close to each other. This solution works
as far as the power is concerned. In order to increase the power used by the propeller, we
increased the speed parameter to 38 mph from 36 mph in the power budget. With the higher
speed parameter, the drag force may also increase, however using drag data that had been
gathered by previous years the drag force for the new speed is extremely close to the drag that
was already on the power budget. The next design iteration is intended to reduce the blade area
while increasing the efficiency of the propeller. Figure O.4 illustrates the first proposed design to
be manufactured.
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Appendix 51
APPENDIX O: SPRINT PROPELLER DESIGN ITERATIONS
Figure O.4. 3rd 3-Blade design consideration intended to increase efficiency and reduce area
between blades
Table O.4. 3rd 3-Blade design operating characteristics
# of Blades
3
Efficiency
72%
Diameter
7.32 inches (0.186 m)
Thrust Produced
258.5 lb (1150 N)
Torque
38 ft-lb (51.5 N-m)
Operating RPM
5000 RPM (523.6 rad/sec)
Boat Speed
38 mph (61.2 kph)
Power Required
36.2 hp (27.0 kW)
The propeller in Figure O.4 is designed to operate at 72% efficiency, and has reduced blade area
at the base of the blades to be machined more easily. This design satisfies the power
requirements, the thrust and speed requirement as seen in Table O.4, and has higher efficiency
than was originally set in the original power budget
Solar Boat Final Report 2013-14
Appendix 52
APPENDIX P: FEA OF HULL WITHOUT DECK ATTACHED
APPENDIX P: FEA OF HULL WITHOUT DECK ATTACHED
Appendix P provides an
example of how we set up our
mesh, applied loads, and
boundary conditions for our
FEA in SolidWorks
Simulation. Our example here
is for case 1 – hull during the
Sprint event as shown in
Figure P.1 First, we split the
Figure P.1: Image of hull during Sprint event
Figure P.2. Hull before and after surfaces have been split in order to apply loading
conditions in proper regions
Table P.1. Loads applied in Figure
P.3 (in direction of arrows on FBD)
Component
Figure P.3. Case 1, Sprint configuration, Sprint event
with loads applied and boundary conditions set
Solar Boat Final Report 2013-14
Endurance Drivetrain
R1z
Sprint
R1y
Drivetrain R2z
R2y
Motor Controllers
Batteries
Hull
Driver
Buoyancy
Drag
Weight
[lb]
24
-268
30
492
30
51
100
100
155
512
225
Appendix 53
APPENDIX P: FEA OF HULL WITHOUT DECK ATTACHED
surface of the hull into the various loading regions in order
to apply our loads. A screen capture of this can be seen
below in Figure P.2. Next, we applied our loads as can be
seen below in Figure P.3. The loads applied are specified
in Table P.1.
Once we had applied our loads and set our boundary
conditions, we then defined the material as a composite
layup and defined the material properties and orientation of
our skin and core as using Surface Mapping as shown in
Figures P.4 and P.5. For our analysis we modeled the
woven fabric as two layers of uni-directional fibers layered
on top of one another.
Next, we created our mesh. We utilized tetrahedral shell
elements with a maximum length of 1.0 in. The mesh we
used for the specific example is shown in Figure P.6.
When our mesh was defined with 1.0 in as the maximum
side length, our solution varied very little with our solution
when using a more refined element size. Thus, we chose to
use 1.0 in as our standard for the maximum length of our
Figure P.5. Hull with faces selected for defining
material properties and orientation (transom
defined separately)
Solar Boat Final Report 2013-14
Figure P.4. Display for selecting
composite type and orientation.
Figure P.6. Tetrahedral shell elements with
maximum side length of 1.0” and no refinement
Appendix 54
APPENDIX P: FEA OF HULL WITHOUT DECK ATTACHED
shell sides in order to save run time and make the SolidWorks files easier to work with as using a
more refined mesh quickly slowed the computer when trying to view any results.
Finally, with our loads applied,
boundary conditions set, material
properties (published values used for
High stress regions
of most concern
results shown) and fiber orientation
set, and our mesh created, we ran our
solution and analyzed the results.
Figure P.7 is just 1 example of the
results we obtained from our analysis.
This specific example shows the 1 st
principal stress on the outer skin.
On the following page you can see the
free body diagrams (FBD’s) for the
other 3 cases run displayed in Figures
Q.8-10. The results from case 2 (hull
in Sprint configuration on trailer)
Figure P.7. 1st principal stress on outer skin of hull
with 1.25” core in planning portion and 0.472” core
above chine line (2nd to last composite schedule
iteration) (deflections magnified 20x). Transom is not
an area of serious concern since stiffer core is used in
that region
indicated that stresses and deflections
for this loading case are significantly less than those of either case 1 or case 3. Results from case
3 (hull in Sprint configuration lifted from bow and stern) showed similar deflections to those in
case 1 (hull during Sprint event) and the maximum compressive stresses. Case 4 (100 ft*lb
torque applied at bow with transom fixed) yielded lower stress and deflection values than either
case 1 or case 3. Thus, cases 1 and 3 were analyzed the most when making design decisions.
Solar Boat Final Report 2013-14
Appendix 55
APPENDIX P: FEA OF HULL WITHOUT DECK ATTACHED
Figure P.8. Case 2, Sprint
configuration, on trailer with loads
applied and boundary conditions set
Figure P.9. Case 3, Sprint
configuration, lifted from bow and stern
with loads applied and boundary
conditions set
Figure P.10. Case 4, artificial case,
100 ft*lb torque applied at bow with
transom fixed
Solar Boat Final Report 2013-14
Appendix 56
APPENDIX R: HULL MANUFACTURING TECHNIQUES
APPENDIX Q: MECHANICAL TESTING OF HULL MATERIALS
Appendix Q covers the test setups used and documented results considered when making the
final materials selection for the 2014 hull and deck. As identified earlier, there were several tests
which we identified as critical for selecting the new composite schedule for the 2014 Solar
Splash hull, which will hopefully serve as the staple composite schedule for Cedarville
University in the years to come, and help us to claim many more Solar Splash titles, and even
future DSC titles. We will cover the test setups and results in the following order: tension, short
beam (interlaminar shear), long beam (bending stress and skins buckling), and impact.
Tension Test First, the tension test.
Shown in Figures R.1 (below) and 6B.2
(right) is the final iteration of tension test
specimens used. Please refer to Figure Q.3
Figure Q.1. Standard test coupon for all
tension tests
(bottom right) for an image of our
Figure Q.2. Carbon fiber test specimens for
tension testing before and after failure in tension
test
test setup. The testing standards
established for this test were
partially the result of research,
experimentation, and iteration.
Based on this testing, we were
Internal Tracking
Number
able to determine the ultimate
2 plies in
tensile strength, load carried per
clamping
unit width of specimen (critical
region
for our results since we are only
looking for a skin which is 1 layer
of fabric thick), and Young’s
Solar Boat Final Report 2013-14
Figure Q.3. Kevlar sample shown in tension test machine
before and after failure
Appendix 57
APPENDIX R: HULL MANUFACTURING TECHNIQUES
modulus for several different materials. Some of the key results which helped us to determine
the optimal material from which to construct our skins are displayed below in Figure Q.4. These
results are averaged from samples of 4 or more specimens. The standard displacement rate for
all tests was 0.5 mm/min.
Figure Q.4. Plot showing the amount of load carried by one ply of fabric divided by the width of
the specimen (25 mm average, see Figure Q.1) for various fabric types.
Short Beam Test Also, we performed a short beam bend test in order to determine if
interlaminar shear might cause delamination between the skin and the core. By reducing the
specimen’s span length to height ratio we can cause shear stress to surpass bending stress as the
critical stress. This means that the beam should fail do to shear stress, and not buckle due to
bending stress as in a typical 3 point bend test. Shown below in Figure Q.5 is a dimensioned test
specimen for our short beam bend test. Next, we loaded the test specimens on the Instron and a
point load using a 1 in radius load cell, as shown in Figure Q.6, and loaded until failure, which
for these specimens was compressive and shear failure in the core which caused the loading to
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Appendix 58
APPENDIX R: HULL MANUFACTURING TECHNIQUES
drop. Figure Q.7 shown below contains the results for maximum loading applied for each
specimens constructed of 6 oz., 2x2 twill weave carbon fiber skins, with a 0.5 in aramid fiber
honeycomb core. For these specimens MAS Low Viscosity Epoxy Resin with Fast Hardener
was used. Based on our results we discovered that, for this material layup, because shear stress
is minimal between the skin and core since shear stress is maximum at the neutral axis and
decreases as we move away from the neutral axis, interlaminar shear stress is not an issue. For
all 6 specimens tested, shear and compressive failure in the core served as the critical parameters.
Figure Q.5. Dimensioned test
specimen used for short beam bend test
Core failure region
Figure Q.6. Short beam bend test at
failure. Notice compressive and shear
failure in core.
Figure Q.7. Load at failure for carbon fiber
specimens. No specimens failed due to interlaminar
shear which adds confidence to our hypothesis that
the skin and core will not delaminate.
Thus, we did not perform this test for future specimens of similar layups, but concluded that
delamination due to standard shear stresses was not a major concern. As specimens loaded at a
rate ranging from 0.5 mm/min to 2.0 mm/min exhibited the same results, this test was run at 2.0
mm/min to reduce testing time per sample from 20-30 minutes down to 5-7 minutes.
Long Beam Test Next, we will cover the long beam test used to discover the flexural
stiffness of various composite layups, specifically comparing the stiffness of Kevlar and carbon
fiber. The standard test coupon used in this test is shown dimensioned on the following page in
Figure Q.8. As in the short beam bend test, we applied a compressive load using a 1 in radius
loading cell and applied a load at a constant displacement rate (0.5 mm/min for the 3 point bend
test) until the specimens failed. The modes of failure for all specimens tested was either
buckling of the upper skin due to the compressive stresses, allowed by compressive failure of the
core material (See Figure Q.9) or buckling failure of the upper skin due to compressive stresses,
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Appendix 59
APPENDIX R: HULL MANUFACTURING TECHNIQUES
Figure Q.8. Dimensioned test specimen used for 3 point bend test
Figure Q.9. Close up of buckling failure
in upper skin due to the compressive
stresses initiated by preliminary core
failure
Figure Q.10. Close up of buckling failure
in upper skin due to the compressive
stresses initiated by delamination
allowed by delamination
between the skin and core (See
Figure Q.10). The averaged
results (minimum sample size
of 3 specimens) for load as a
function of –y displacement of
the loading cell is shown in
Figure Q.11 to the right. Based
on our results we were able to
calculate the compressive stress
in the upper skin to be
approximately 15000-25000 psi
for both Kevlar and carbon
fiber specimens (assuming all
bending stress is carried by
Solar Boat Final Report 2013-14
Figure Q.11. Kevlar fabric exhibits much more deflection while
still retaining good load carrying capabilities when compared to the
6.0 oz woven carbon fiber fabric
Appendix 60
APPENDIX R: HULL MANUFACTURING TECHNIQUES
skins). As expected based on our values for Young’s modulus determined in the tension test,
samples using Kevlar skins exhibited lesser, but still somewhat similar max loading (33% lower
max loading), and deflected approximately 75% more than carbon fiber specimens for the same
core thickness.
Impact Test Finally, we performed impact tests to help determine the optimal material
from which to construct our new lightweight hull and deck. An image of the drop test tower
which we constructed in order to complete our testing
can be seen in Figure Q.12 to the left. This homemade
testing machine thus predict the amount of energy
Impacter
absorbed by a specimen at failure. As a means of
comparing various specimens, the standard which we
used was a drop weight of 2.45 lb from 17 in. This
correlates to an energy absorption of 3.45 ft*lb with
times a specimen absorbed this 3.45 ft*lb of energy
without failing (see images R.13, 14 for more insight).
Figures R.13, 14 (left) show one specimen during and
after testing. Finally, in Figure Q.15 on the following
page are the results obtained through our impact
Test
Specimen
testing. It is here that we see the benefits of using
Kevlar, specifically Kevlar with MAS resin.
Figure Q.12. Impact testing drop tower with
sample ready for testing
4 in
Clear
puncture
Indent but
no puncture
4 in
Figure Q.13. Impact testing sample after 1 hit
of 3.45 ft*lb of energy
Solar Boat Final Report 2013-14
Figure Q.14. Impact testing specimen
showing clear indication of failure
(punctured skin)
Appendix 61
APPENDIX R: HULL MANUFACTURING TECHNIQUES
Figure Q.15. Kevlar fabric exhibits the greatest impact toughness compared to carbon fiber,
fiberglass, and Kevlar/carbon fiber bi-weave fabric. Also, MAS Epoxy resin exhibits much
greater impact toughness than Adtech 820 resin.
Solar Boat Final Report 2013-14
Appendix 62
APPENDIX R: HULL MANUFACTURING TECHNIQUES
APPENDIX R: HULL MANUFACTURING TECHNIQUES
After significant testing and experimentation, the 2014 Solar Boat team has determined a
lightweight composite schedule and the necessary manufacturing techniques to be used for
successful lightweight hull construction. This appendix outlines the composite schedule and the
techniques selected and used to manufacture the new lightweight hull and deck for the 2014
Solar Splash hull. This appendix will hopefully serve as an invaluable resource for future year’s
teams.
Composite Schedule First, we will discuss the
composite schedule, as previously mentioned in the
Design Methodology portion of this report. For both the
inner and outer skin we used 1 layer of 5.0 oz 2x2 twill
5.0 oz Kevlar
0.472 in Nomex
honeycomb
0.472 in Nomex
honeycomb
0.58 oz
Fiberglass
weave Kevlar fabric. We utilized 1 layer of 1.8 lb/ft3,
1.25 in thick Nomex honeycomb from the transom to
5.0 oz Kevlar
165 inches in the direction of the bow, and 2 layers of 1.8
lb/ft3, 0.472 in thick Nomex honeycomb with a layer of
0.58 oz/yd2 to bond the two layers together for the
1.25 in Nomex
honeycomb
remainder of the hull (165 inches to transom
[210 inches]). The two core arrangements are shown in
Figure R.1. Cross section of
composite schedule used for
chines/sidewalls
(top) and planing
3
For the transom, we used a 1 in infusion ready 5 lb/ft
portion (bottom)
polypropylene core. While the core itself weighs 5 lb/ft3 , the skin bonded to the honeycomb
Figure R.1.
which prevents resin from filling the part adds another 2 lb/ft3 . However, this still weighs less
than half of the lightest Coosa board (15
lb/ft3 ),
5.0 oz Kevlar
correlating to a weight reduction of
approximately 2.5 lb. For the bow and
the transom corners, we also used a 2 part
expansion foam to increase the structural
1.0 in infusion
ready honeycomb
0.50 oz Kevlar
veil
integrity of those regions and to meet the
buoyancy requirement, rule 7.14.2.
Finally, to increase the stiffness of the
Solar Boat Final Report 2013-14
Figure R.2. Cross section of composite schedule
used for the transom. The 0.5 oz Kevlar veil falls
between the mold wall and the core.
Appendix 63
APPENDIX R: HULL MANUFACTURING TECHNIQUES
boat as a whole, provide a mounting point for the steering system, and provide an aesthetically
pleasing edge, we utilized wooden gunnels. For an illustration of the composite schedule used,
please refer to Figures S.1 and S.2 shown on the
previous page.
The 0.50 kevlar veil shown in Figure O.1 is
utilized to better allow for good resin distribution
through the outer layer of 5.0 oz Kevlar
sandwiched between the mold surface and the
core. See Figures S.3 and S.4 for a better
understanding of this. Also, to better encourage
Figure R.3. Resin flow when not using 0.5
oz Kevlar veil with 5.0 oz Kevlar fabric is
very limited (through hole added).
resin flow throughout the Kevlar sandwiched
between the mold surface and the core, we drilled
through holes 4 in on center (OC) throughout the
core. See Figure R.5 below.
Figure R.4. Using 0.5 oz Kevlar veil
promotes much better resin distribution
within skin sandwiched between mold wall
and infusion ready core (no through holes
added).
Solar Boat Final Report 2013-14
Figure R.5. Drilling through holes 4 in OC in 1 in
thick infusion ready core to allow for better resin
flow.
Appendix 64
APPENDIX R: HULL MANUFACTURING TECHNIQUES
Composite Manufacture Next, we will cover the manufacturing techniques used to
construct the new 2014 Solar Splash hull, beginning with the initial cleaning of the mold and
finishing with the final product.
Prepare Mold
1. Clean mold
It is absolutely critical that the mold be thoroughly cleaned before sealing and waxing in
order to create a smooth surface on the finished part and allow for an easy release of the
part from the mold. For this step first blow the mold out using compressed air. Then,
take a damp (acetone, not water) rag and wipe it
over the surface of the mold to remove any wax,
spray tac, and dust from the mold (see Figure
R.6). Gloves are recommended while using
acetone, or else your hands will be thoroughly
dry when you are done since acetone evaporates
so quickly. If any resin remains on the part,
remove it with a putty knife while taking care not
Figure R.6. Clean mold with
acetone
to scrape the mold before cleaning with acetone.
2. Seal mold (unnecessary if mold has been sealed within last 2-3 months and not been cleaned
with acetone since last sealing)
Once the mold has been thoroughly cleaned, it is
now time to seal and wax the mold. Apply 2
coats of liquid sealant (Finish Kare “Total”,
#135-80 polymer mold cleaner, wax remover,
and sealant used in 2014) by wetting out a clean
rag with the sealant, wiping it onto the mold,
waiting 10 – 15 seconds, and gently wiping dry
with another clean rag (see Figure R.7). Do not
attempt to wet out and seal areas larger than 15
Figure R.7. Seal mold with liquid
sealant
ft2 at once, but wet the mold out in regions.
3. Apply liquid wax
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Appendix 65
APPENDIX R: HULL MANUFACTURING TECHNIQUES
If the mold has recently undergone a full wax
cycle and a part has been removed in the recent
past (1-2 weeks), apply 1 coat of liquid wax
(Airtech, Safelease #30, water-based P.T.F.E.
mold release agent used in 2014). Otherwise, if
this is part of the full wax cycle necessary if the
mold has not undergone a full wax cycle in the
recent past, apply 2-3 coats of liquid wax using the same process as outlined above for
liquid sealant (see Figure R.8).
4. Apply paste wax
If the mold has undergone a full wax cycle and a
Figure R.8. Wax mold with liquid
wax
part has been removed in the recent paste (1-2 weeks), apply 1 coat of paste wax (Rexco,
hi-temp mold release wax used in 2014).
Otherwise, if this is part of the full wax cycle
necessary if the mold has not undergone a full
wax cycle in the recent past, apply 2-3 coats of
paste wax. Apply wax with rag, Figure R.9, or
wax applicator, and wipe gently with clean rag
until rag glides smoothly over the mold. Do not
attempt to apply wax to areas larger than 10 ft2 at
one time, but wax the mold in regions.
Solar Boat Final Report 2013-14
Figure R.9. Wax mold with paste
wax
Appendix 66
APPENDIX R: HULL MANUFACTURING TECHNIQUES
Gel Coat (if necessary)
We, the 2014 Solar Boat team, gel coated only the outer skin of the hull. This provides UV
protection, a smooth finish we can be buffed to further smooth it, and an aesthetically pleasing
surface.
1. Run masking tape around mold flange
Once the mold has been fully prepared as outlined above,
we can go ahead and prepare for gel coating by first lining
the mold flange with masking tape (see Figure R.10),
allowing for a bondable surface for the sealant tape once
the part has been gel coated and the masking tape
removed.
2. Mix gel coat with catalyst
Using 1-3% MEKP-9 (1.5% used for the 2014 Solar
Figure R.10. Run masking
tape around mold flange
Splash hull), or similar catalyst, depending on temperature and humidity, mix catalyst
with gel coat. Once the catalyst has been mixed you have 15-60 minutes of working time
depending on temperature, humidity, and amount of catalyst used. Higher temperatures
will accelerate the gel time considerably (increase of 12 °F will approximately cut gel
time and half and decrease of 12 °F will approximately double gel time). Also,
increasing amount of catalyst has a significant effect on gel time until 4% catalyst or
more is used.
3. Spray mold to 10 mils thick
Once the gel coat has been thoroughly mixed, apply to mold
with a cup gun (see Figure R.11). Cup guns allow for slow
buildup of gel coat and a nice even coat. Check depth using
a depth gauge periodically to ensure that your desired
thickness is met (10 mils used in 2014 which projects to 5 lb
of gel coat).
Figure R.11. Spray
mold with gel coat to 10
mils thick using cup gun
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Appendix 67
APPENDIX R: HULL MANUFACTURING TECHNIQUES
Infusing Skins
1. Prepare patterns
This step does not have to occur now, but can occur any time up until this point. For this
step, patterns are marked, cut, and checked (see Figure R.12 below) to serve as guides for
cutting the fabric, release fabric, and flow medium in the future.
Figure R.12. Mark, cut, and check pattern.
2. Cut fabric to pattern and place in mold
Once the mold has been properly prepared, with the appropriate amount of wax applied
and gel coat sprayed (if necessary), we can begin to cut the fabric. Since this step is selfexplanatory, and we will not cover it further except to refer you to Figure R.13.
3. Cut release fabric to pattern
When cutting the release fabric, it is critical
that you cut it several inches (2 in is
recommended) larger than the pattern so
that it may fully cover the Kevlar, or other
fabric used as mentioned is step 2
immediately above.
4. Cut flow medium to pattern
When cutting the flow medium, it is
generally a good idea to cut it slightly larger
than the fabric used, but slightly smaller
than the release fabric used. As a general
guideline, cutting the flow medium 1 in
larger than the pattern is recommended.
Solar Boat Final Report 2013-14
Figure R.13. Mark and cut fabric to pattern.
Use same method with slight modifications as
outlined in steps 3 and 4 for the release fabric
and flow medium
Appendix 68
APPENDIX R: HULL MANUFACTURING TECHNIQUES
5. Lay fabric, release fabric, and flow medium in mold.
This step is self-explanatory, and we will not cover it further except to refer to the image
below, Figure R.14).
Figure R.14. Left to right: lay fabric, release fabric, and flow medium into
mold.
6. Trim away excess
Trim away excess fabric, release fabric, and flow medium leaving roughly a 1 in strip
around the mold flange for the sealant tape. Ensure that the release fabric spreads past
fabric to ensure that flow medium does not infuse to fabric.
7. Lay spiral tubing, bag part, and run resin lines
Cut spiral tubing and begin to bag part. We recommend that spiral tubing be placed
along the keel line as the resin feed line, and spiral tubing be run along the entire gunnel
region as the resin outlet. It is important that the spiral tubing used as the resin outlet,
running to the reserve tank, that small breaks be made so that the spiral tubing has small
breaks midway between any tees preventing resin from flowing through the spiral tubing
Figure R.15. Left to Right: prepare spiral tubing for resin inlet and outlet, bag part, and
run resin lines from resin outlet to reserve tank, reserve tank to vacuum pump, and resin
inlets to one common point.
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Appendix 69
APPENDIX R: HULL MANUFACTURING TECHNIQUES
around the mold flange from the bow to the transom region before the transom region has
had resin fill the sidewalls of the mold. For further understanding, see Figure R.15.
Then, with the spiral tubing in place and the part bagged, finish running the resin tubing
connecting the resin outlets to the reserve tank and the reserve tank to the vacuum pump.
8. Infuse part.
Mix resin according to specified ratio, place resin inlet tubes into mixed resin pot, and
unclamp resin inlet lines allowing resin to flow into part. Clamp off resin outlet lines
when resin begins leaving through each individual resin outlet until entire part is filled
with resin. Once part has fully infused, clamp of resin inlet lines also.
9. Remove bagging material, release fabric and flow medium, and demold part as shown in
Figure R.16 below, taking care not to bend the skin.
Figure R.16. Remove bagging material and then gently peel back
release fabric taking care not to wrinkle the skin.
10. Repeat process for 2nd skin with the following adjustments made for the second skin
involving the transom.
Prepare transom core piece as shown above in Figure R.5. Also, round of corners so that
it fits tightly into the mold adding 1 layer of 0.5 oz Kevlar veil between the mold surface
and core material as shown above in Figure R.2.
Inserting Core and Bonding Skins
1. Sand surface of inner skin which will come in contact with core material.
2. Prepare patterns
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Appendix 70
APPENDIX R: HULL MANUFACTURING TECHNIQUES
This step does not have to occur now, but can
occur any time up until this point. For this step,
patterns are marked, cut, and checked (see
Figure R.17 below) to serve as guides for
cutting the core material.
3. Mark and cut core material using patterns
Carefully outline the patterns onto the core
Figure R.17. 2 of 5 pattern pieces cut
created for cutting core
material and cut to size. Remember to cut proper angles on core material for fitting into
corners and meeting other pieces. A sharp knife works well for this purpose. See Figure
R.18 below.
Figure R.18. Trace pattern onto core material and cut core
material to pattern taking great care to cut the proper
angles.
4. Lay core on outer skin and check for proper fit
Self explanatory. See Figure R.19 below.
Figure R.19. Lay core material on outer skin and check for proper fit
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Appendix 71
APPENDIX R: HULL MANUFACTURING TECHNIQUES
5. Mark and cut inner skin
Mark and cut the inner skin such that it will be
able to adhere to the core material. See Figure
R.20 for mor information.
6. Lay inner skin on core and check for proper fit
Self explanatory. See Figure R.21 below.
Figure R.20. Inner skin with cut
lines marked in orange.
Figure R.21. Lay inner skin on core material and
check for proper fit.
7. Clean skins and core
Remove any dirt or debris from bonding surface of skins and from core material to ensure
a good bond.
8. Wet out outer skin
Using a paint roller and paint brush, apply a thin coat of
resin to the bonding surface of the inner skin. Make sure
that any surface that will come in contact with core material
has been wetted out with resin. See Figure R.22.
9. Lay core material and place fabric strips
Lay the core material back into the mold one piece at a time
and wrap edges of core material at seams with fabric tape
Figure R.22. Wet outer
skin in preparation for
bonding with core
wetted out with resin. Also, run fabric along outer rim to
bond the skins along the gunnel region (this may be done after the skins and core are
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Appendix 72
APPENDIX R: HULL MANUFACTURING TECHNIQUES
bonded). This tape will help the skins to adhere to one another. The 2014 Solar boat
team used a 4 oz/yd2 fiberglass. See Figure R.23.
Figure R.23. Lay core material in one piece at a time and wrap seams with wetted out
fabric.
10. Wet out inner skin, place on core, and lay fabric over seams
Wet out the bonding surface of the inner skin using the same paint roller, or like tool,
from before. Then carefully place these strips on the core material. Wet out fabric (2014
used a 4 oz/yd2 fiberglass fabric and a 5 oz/yd2 Kevlar for the varoius seems) and lay
along seems to bond the inner sking back together. Seem Figure R.24 below.
Figure R.24. Lay wetted out pieces of inner skin back in mold and lay wetted out fabric
strips along seams (this last step may be done after the skins and core are bonded.
11. Bag part and pull vacuum to 5 inches of Hg
Bag part, but do not use release fabric and flow medium, or spiral tubing. One vacuum
outlet will be sufficient. Let hull sit for several days until resin is completely dry (thin
films take longer to set than published times) while maintaining constant vacuum
pressure.
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Appendix 73
APPENDIX R: HULL MANUFACTURING TECHNIQUES
12. Remove bagging and release hull from mold
Remove bagging material and release part from mold. The hull should be able to stand
alone now.
13. Add gunnels and mount stearing system.
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Appendix 74
APPENDIX S: FLUENT INPUT CONDITIONS
APPENDIX S: FLUENT INPUT CONDITIONS
In order to simulate the water and air flowing around the Solar Boat in Fluent we were required
to first setup the simulation in Fluent before running it. Tables U.1-U.2 below lay out all of the
conditions set in Fluent on how this was done.
Table S.1. This is the conditions selected in the Solution Setup tab inside Fluent. The various other options in
Fluent not listed in the Solution Setup tab were left as defaults, this table only lists those that we were required to
adjust to simulate the flow around the boat.
Solution Setup:
General:
Solver:
Gravity:
Pressure-Based
Absolute
Transient
Enabled
Y: (m/s2)
-9.81
Models:
Multiphase:
VOF:
2 Eulerian Phases
Explicit Scheme
Body Force Formulation - Enabled
k-epsilon:
RNG
Non-Equilibrium Wall Functions
Viscous:
Materials:
Fluid:
air
water-liquid
Phases:
air - Primary
water - Secondary
Cell Zone Conditions:
Operating Conditions:
Boundary Conditions:
Symmetry:
Outflow:
Interior:
Velocity-Inlet:
Wall:
Reference Values:
Area (in2)
Density (kg/m3)
Length (in)
Velocity (mph)
Viscosity (kg/m-s)
Solar Boat Final Report 2013-14
Specified Operating Density - Enabled
Operating Density (kg/m3):
1.225 (always lowest of two fluids)
sides
top
outlet
int_inner_box
int_live
int_fluid
Multiphase for Inlets:
inlet_air
0 VF
No Water
inlet_water
1 VF
All Water
All 6 boat pieces
bottom =
Moving Wall at 9mph in -Z direction (Important)
721
998
210
9
1.003E-03
Appendix 75
APPENDIX S: FLUENT INPUT CONDITIONS
Table S.2. This is the second section of the conditions input into Fluent to calculate the drag on the Solar Boat hull.
This specific table shows the conditions used in the Solution and Reports tabs in Fluent. The mos t important thing
to note here is the solution needs to be patched as shown in the Solution Initialization section.
Solution:
Solution Methods:
Scheme:
Coupled
Spatial Discretization:
Gradient: Green-Gauss Cell Based
Pressure: Body Force Weighted (Important)
Solution Controls:
Under-Relaxation Factors:
All set to 0.5 (Important)
Monitors:
Setup Drag and Lift to monitor boat
Drag in -Z
Lift in +Y
Solution Initialization:
Compute from Inlet_Water first
Adapt -> Cell Above Wate r-> Patch -> Phase - Water - Volume Fraction - 0
Run Calculation:
Time Step Size (s):
0.001 (any higher and it will fail)
Number of Time Steps:
Usually need 2000 to converge
Reports:
Forces:
Select Boat wall zones
1 in Y = Lift
(-1) in Z = Drag
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Appendix 76
APPENDIX T: INITIAL STRAIN GAGE TEST
APPENDIX T: INITIAL STRAIN GAGE TEST
For the first calibration test of the strain gage mounting device we used a test downleg section as
shown in Figure T.1. Each gage was connected to a strain indicator box as a quarter bridge and
weights were applied with the downleg placed vertically and horizontally in the vice.
Additionally the 6 gages were connected as a hull-bridge (to measure thrust) and half bridge (to
measure-torque) and the same load test was done as with the quarter-bridges. Figures W.2-5
show the strain vs. weight applied curves for each of the tests just described.
Figure T.1. This figure shows both the vertical (top) and horizontal (bottom two) load tests done
of the test strain gage tube. The data from this test is shown in Figure T.2-5 below. Additionally,
the gage numbering legend is located on the far right of this image and the bright red strip on the
downleg section marks the location of the strain gages.
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Appendix 77
APPENDIX T: INITIAL STRAIN GAGE TEST
Vertical Loading
100
80
Micro Strain
60
Gage 1
40
Gage 2
20
Gage 3
0
-20 0
5
10
15
20
25
Gage 4
Gage 5
-40
Gage 6
-60
-80
Load (lb)
Figure T.2. This figure shows the data from the vertical load test. Gages 1 and 4 overlay
each other because they mirror each other as shown in the far right image in Figure T.1.
Gage pairs 2, 5 and 3, 6 also overlay each other. Something to note as well, Gage s 2 and 5
should read 0 strain for this entire test as they are on the neutral axis.
Horizontal Loading
100
Gage 1
Micro Strain
50
Gage 2
Gage 3
0
0
5
10
15
-50
20
25
Gage 4
Gage 5
Gage 6
-100
Load (lb)
Figure T.3. This figure shows the data from the horizontal load test, when the downleg was
clamped at its side. For this test, we expected gages 1-3 to be positive and gages 4-6 to be
exactly the opposite as 1-3. You can clearly see from this graph that our test was successful as
the gages behaved as expected.
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Appendix 78
APPENDIX T: INITIAL STRAIN GAGE TEST
Half-Bridge
0
-20
0
5
10
15
20
25
Micro Strain
-40
-60
-80
-100
-120
-140
y = -7.3814x - 2.3557
R² = 0.9997
-160
Load (lb)
Figure T.5. This figure shows the data from the half-bridge calibration test. The
horizontal test setup was used for this test as shown in Figure J.1. As seen in the graph
the data was nice and linear which we expect from this test. The trend line calculated
with excel can we used to convert all of the strain readings from the Solar Boat into
torque.
Full-Bridge
0
0
5
10
15
20
25
Micro Strain
-50
-100
-150
-200
-250
-300
y = -12.785x - 4.711
R² = 0.9992
Load (lb)
Figure T.4. This figure shows the data from the full-bridge calibration test. The vertical
test setup was used for this test as shown in Figure T.1. As seen in the graph the data
was nice and linear which we expect from this test. The trend line calculated with excel
can we used to convert all of the strain readings from the Solar Boat into thrust in
pounds.
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Appendix 79
APPENDIX U: FINAL STRAIN GAGE TEST AND CHARACTERIZATION
APPENDIX U: FINAL STRAIN GAGE TEST AND CHARACTERIZATION
With the strain gages applied inside the forward facing propeller downleg, we next
needed to calibrate the strain gages to make sure we could understand what our measurements
meant in terms of thrust and torque. To date only the thrust characterization test has been
completed using the support location if the endurance propeller is made to be 14 inches in
diameter. An additional test is planned at another support location, this will confirm that we can
simply adjust the moment to modify the data.
To calibrate the strain gages for torque a mounting bracket that will wrap about the pod
attached to the downleg has been sketched and is in the process of being manufactured. Once
completed, a test will be done to calibrate the torque by applying a moment perpendicular to the
downleg to simulate pure torque.
As for the thrust calibration test, Table U.1 and Figures U.1-2 show the setup and data recorded.
The trend line through the plotted data will be used to translate the strain data into thrust which
will be compared to the CFD drag analysis.
Total Weight [lb] Full-Bridge Half-Bridge
Weight [lb] (weights + hanger)
Micro Strain
0
0.575
0.0
0.0
2
2.575
8.0
0.0
4
4.575
17.0
-1.0
6
6.575
25.5
-1.0
8
8.575
34.0
-1.5
10
10.575
43.0
-2.0
12
12.575
51.0
-2.5
14
14.575
59.5
-3.0
16
16.575
68.0
-3.0
18
18.575
77.5
-4.0
19
19.575
82.0
-4.0
18
18.575
77.0
-4.0
16
16.575
68.5
-3.5
14
14.575
60.0
-3.0
12
12.575
51.0
-2.5
10
10.575
42.0
-2.0
8
8.575
34.0
-1.5
6
6.575
25.5
-1.0
4
4.575
16.5
-1.0
2
2.575
8.0
0.0
0
0.575
-1.0
0.0
Table U.1. This is the data collected during the
thrust calibration test. The total weight represent
the weights applied to the hanger as well as the
hanger itself.
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Appendix 80
APPENDIX U: FINAL STRAIN GAGE TEST AND CHARACTERIZATION
Thrust Calibration Test
90
y = 4.3057x - 2.8234
R² = 0.9998
80
70
Micro Strain
60
50
40
30
20
10
y = -0.2186x + 0.2916
R² = 0.9809
0
-10
0
5
10
15
20
25
Load [lb]
Figure U.1. Graph plotting the strain data vs. the loading. The orange and blue lines are
overlapping because they show the hysteresis as well as the yellow line. The yellow line shows
the two gages located on the neutral axis. All of the readings for the gages on the neutral axis
should be zero, however we were not able to mount the gages perfectly.
Figure U.2. This is the test setup for the strain gage thrust calibration test. We used a wooden rod with
string to attach the hanger shown toward the left to apply the load. The vice is clamped at the position
we expect the downleg to be attached to the boat.
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Appendix 81
APPENDIX V: OHIO SUPERCOMPUTER CENTER INSTRUCTIONS
APPENDIX V: OHIO SUPERCOMPUTER CENTER INSTRUCTIONS
In an attempt to gain more computing power to running multiple large CFD simulations at once
we pursued several different options. We ended up taking advantage of a grant from the Ohio
State Supercomputer, available to all Ohio college research projects. We contacted Barbara
Woodall, a support engineer at OSC. She helped us setup an account, where we had 50,000 cpu
hours to use for all CFD projects across all senior design projects. A cpu hour is calculated as 1
hour of 1 cpu, so a quad-core cpu for one hour would use 4 cpu hours from our allowed time. A
video explaining how to connect to and use the OSC was created in the CFD video tutorial series
located on the T:Drive1 . To access the OSC, there are two different methods. One can either use
3rd party open-source software like PuTTY and WinSCP or use the OSC OnDemand website.
We would recommend using the 3rd party software as it allows the user more control over their
files and submitted jobs. However, if this is not an option see Appendix J.5 for information on
how to access the OSC website and also information on how to setup an account with OSC.
To install the 3rd party software we used to connect to the supercomputer, you will need to
simply google search PuTTY and WinSCP. Once you have both of those installed you will be
able to use WinSCP to drag and drop files from your computer over to the supercomputer and
create job files and journal files. These files are needed to run simulations on the supercomputer.
Sample journal and job files can be found on the T:Drive2 and also explained further in video
series. Figure Y.1 below, shows a screenshot of the commander WinSCP window that is used to
connect to the supercomputer files.
The next big part of the supercomputer that is needed is the interact window that will allow you
to open Fluent files that are larger than 512k cells. This is critical because you will need to setup
the case and data files for the larger meshes before running them on the supercomputer. Figures
Y.2-5 show the process to open Fluent on the supercomputer to setup the case and data files
remotely once the Glenn Desktop is opened from the Apps tab on the OnDemand website.
1
T:\Engineering Competitions \SOLAR BOAT\2013-2014\Photos and Videos\Hull Drag
T:\Engineering Competitions \SOLAR BOAT\2013-2014\Individual Folders\John Howland - CFD\Tutorial
and
Appendix
Sample Files
2
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82
APPENDIX V: OHIO SUPERCOMPUTER CENTER INSTRUCTIONS
Figure V.1. This is a screenshot of the WinSCP program. The left side shows the files
currently on the T:Drive and the right side being the files on the supercomputer.
Figure V.2. Once the Glenn App is opened, go to
Applications  Accessories  Terminal
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Appendix 83
APPENDIX V: OHIO SUPERCOMPUTER CENTER INSTRUCTIONS
Figure V.3. Once the terminal is open, you need to type in the command to request some time. The
only number one in that command is at the very end, the things that look like ones in the middle are
lower case L’s. This is confusing as the OSC website font makes it tough to tell.
Figure V.4. Once the request goes through for the time, you need to request to use Fluent. This can
be typed in whenever. Make sure to use fluent14.5, otherwise it will revert to the default version,
13.
Figure V.5. Once the job is ready, simply type in fluent and it should load the program and you can
be on your way.
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Appendix 84
APPENDIX W: OHIO SUPERCOMPUTER CENTER WEBSITE INSTRUCTIONS
APPENDIX W: OHIO SUPERCOMPUTER CENTER WEBSITE INSTRUCTIONS
Instructions to gain OSC account and online access:
First gain an account with OSC by contacting their support team @ oschelp@osc.edu .
Our contact there is Barbara Woodall, @ woodall@osc.edu . You will need to fill out forms to
use Fluent letting OSC know that you are going to give them credit for whatever work you do on
the supercomputer. Once that is done each team member will be given a user ID and a password.
In order to connect to the supercomputer you will need to use a terminal to port into it.
There are two ways to do this, however this appendix only explains the online method. See
Appendix J.4 for the preferred method. The terminal will allow you to view your files on the
supercomputer, upload/download files, and to submit jobs.
First: Go to https://ondemand.osc.edu/catalog/ with any internet browser you want, we
prefer Google Chrome. Enter your username and password to login, this is the information given
to each student by OSC. Figure W.1 below shows the login screen for the website.
Figure W.1. This is a screenshot of the OSC OnDemand website login page.
This is the initial page before entering the website.
Then click on the Clusters tab and whichever computer you want to use. To find
general info on each cluster simply look around on the OSC website. We used the Glenn cluster
because it has Fluent 14.5 which is the version of the software we use current here at CU. So
with the tab clicked, select the Glenn Shell Access. This will pop-up a terminal window that
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Appendix 85
APPENDIX W: OHIO SUPERCOMPUTER CENTER WEBSITE INSTRUCTIONS
will ask for your password, once entered you will be into the supercomputer and can submit jobs
and check on jobs in progress. See the terminal section for what commands to use in the
supercomputer terminal. Also on the OnDemand website you can access your files and
everything else you would need to do on the supercomputer. Figure Q.2 shows the main screen
you will see once logged into the page, with the Glenn Shell Access tab highlighted.
Figure W.2. Screenshot showing the Glenn Shell Access tab needed to open the
terminal to the supercomputer, which is used to submit jobs.
Solar Boat Final Report 2013-14
Appendix 86
APPENDIX X: CENTER OF GRAVITY SOFTWARE
APPENDIX X: CENTER OF GRAVITY SOFTWARE
This appendix covers the Center of Gravity (COG) software developed by the 2013-2014 Solar
Boat team. This Excel workbook enables the user to quickly utilize the database created to
calculate the COG location, and 1 of 3 other variables (bow depth, transom depth, and weight)
which define the depth of the hull in the water by defining any 2 of the 3 variables listed above.
See Figure X.1 for more clarification on these variables and Figure X.2 for an image of the user
interface. Once these 4 values are all defined, the user can then move to plotting the Endurance
component layout to make sure that the COG and the buoyant force occur at the same location.
This ensures that future Solar Boat
teams load their components
accordingly, such that the transom is
submerged the optimal amount for the
weight of the hull given, resulting the
Figure X.1. Variables used in COG software defined.
Define Water Density
Define 2 of these
3 variables
Buoyant Force Location
Figure X.2. User interface for COG software before and after running the “Search Database”
function.
in the most efficient operating point.
Search Database The first tool for the COG loading software is the “Search Database”
tool. By utilizing SolidWorks, we gathered data relating relationship the displaced volume of
water and the buoyant force location as a function of bow depth, transom depth. See Tables
AA.1 and 2. By defining the density of water in the user interface, the software will create a
similar table to that in Table X.1 except that buoyant force [lb] replaces the displacement volume
[ft3 ]. Then, the program performs a 1D or 2D interpolation, depending on what user input
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Appendix 87
APPENDIX X: CENTER OF GRAVITY SOFTWARE
variables have been defined to determine the 3rd variable from the “Define 2 Values” section of
the user interface and calculates the buoyant force location [in]. For the code used, refer to
“Search Database: VB Code” which is found several pages following.
Table X.1. Database obtained using SolidWorks displaying displaced volume of water as a function of
bow depth and transom depth submerged in the water. Buoyant force is calculated by multiplying this
displaced volume by the user defined input “Water Desnsity [lb/ft^3]”
Displacement Volume as a function of Bow Depth and Transom Depth
Bow Depth [in]
Displacement Volume [ft^3]
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
15.0
9.04
8.41
7.79
7.18
6.57
5.97
5.38
4.81
4.25
3.71
0.0
9.90
9.27
8.64
8.02
7.41
6.80
6.20
5.61
5.03
4.47
3.92
0.5
10.84
10.20
9.56
8.94
8.31
7.70
7.11
6.50
5.91
5.33
4.77
4.23
3.71
11.81
11.17
10.54
9.91
9.28
8.66
8.05
7.45
6.85
6.27
5.70
5.15
4.61
4.09
3.60
12.80
12.15
11.52
10.89
10.26
9.63
9.03
8.42
7.83
7.23
6.65
6.09
5.54
5.01
4.51
4.02
3.56
1.5
2.0
1.0
12.50
11.87
11.24
10.61
9.99
9.38
8.78
8.19
7.61
7.04
6.48
5.94
5.43
4.93
4.45
4.00
3.58
2.5
12.85
12.22
11.59
10.97
10.35
9.75
9.15
8.56
7.99
7.43
6.88
6.35
5.84
5.35
4.89
4.44
4.03
3.64
3.0
12.57
11.94
11.33
10.72
10.12
9.53
8.95
8.38
7.83
7.29
6.77
6.27
5.79
5.33
4.89
4.48
4.09
3.71
3.5
12.92
12.30
11.69
11.09
10.49
9.91
9.33
8.77
8.23
7.70
7.20
6.72
6.22
5.77
5.34
4.93
4.51
4.0
12.67
12.06
11.46
10.87
10.29
9.73
9.18
8.64
8.12
7.61
7.13
6.66
6.21
5.78
5.34
4.5
12.43
11.84
11.26
10.68
10.13
9.58
9.05
8.54
8.04
7.56
7.10
6.65
6.18
5.0
12.81
12.22
11.65
11.08
10.53
9.99
9.47
8.96
8.47
7.99
7.53
7.03
5.5
12.61
12.04
11.48
10.94
10.41
9.89
9.38
8.89
8.41
7.89
6.0
Transom Depth [in]
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APPENDIX X: CENTER OF GRAVITY SOFTWARE
Table X.2. Database obtained using SolidWorks displaying COG location as a function of bow depth
and transom depth submerged in the water
Buoyant Force location as a function of Bow Depth and Transom Depth
Bow Depth [in]
Buoyant Force location [ft]
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
15.0
9.63
9.63
9.62
9.61
9.60
9.60
9.59
9.59
9.60
9.61
0.0
9.29
9.27
9.24
9.21
9.18
9.14
9.10
9.06
9.02
8.98
8.93
0.5
8.96
8.92
8.86
8.82
8.76
8.71
8.65
8.57
8.49
8.40
8.30
8.19
8.06
1.0
8.66
8.60
8.54
8.47
8.40
8.32
8.23
8.14
8.03
7.91
7.77
7.63
7.46
7.27
7.05
8.39
8.33
8.26
8.18
8.09
8.00
7.91
7.79
7.67
7.53
7.38
7.22
7.03
6.82
6.59
6.33
6.04
1.5
2.0
8.02
7.93
7.84
7.74
7.63
7.51
7.39
7.24
7.09
6.92
6.73
6.52
6.29
6.04
5.76
5.45
5.12
2.5
7.72
7.63
7.52
7.41
7.29
7.16
7.02
6.86
6.69
6.50
6.30
6.08
5.84
5.58
5.30
5.00
4.67
4.33
3.0
7.34
7.23
7.11
6.97
6.83
6.68
6.55
6.33
6.14
5.93
5.70
5.46
5.20
4.93
4.64
4.33
4.02
3.69
3.5
7.07
6.95
6.82
6.68
6.53
6.37
6.20
6.01
5.81
5.60
5.38
5.15
4.88
4.62
4.34
4.06
3.76
4.0
6.69
6.55
6.41
6.25
6.09
5.91
5.72
5.52
5.31
5.09
4.86
4.61
4.36
4.11
3.83
4.5
6.30
6.15
6.00
5.83
5.65
5.46
5.26
5.06
4.84
4.61
4.38
4.15
3.89
5.0
6.07
5.92
5.76
5.59
5.41
5.23
5.03
4.83
4.62
4.40
4.19
3.94
5.5
5.70
5.54
5.37
5.20
5.01
4.82
4.63
4.43
4.22
3.99
6.0
Transom Depth [in]
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Appendix 89
APPENDIX X: CENTER OF GRAVITY SOFTWARE
Sub SearchDatabase()
'
'this macro determines the bow height, transom depth, or buoyant force based on given user inputs
'
'run this macro by entering the following keystroke "ctrl+shft+d"
'
'turns off screen updating
Application.ScreenUpdating = False
'Defines active sheet name
sht_name = ActiveSheet.name
'ends program if buoyancy database sheet is active
If sht_name = "Buoyancy Database" Then
MsgBox ("Error. Cannot run program from 'Buoyancy Database' sheet. Program will stop executing.")
GoTo 200
End If
'makes buoyancy database sheet visible for calling data
Sheets("Buoyancy Database").Visible = True
'assigns user inputs
bow_d = ActiveSheet.Range("C6").Value
transom_d = ActiveSheet.Range("C7").Value
Weight = ActiveSheet.Range("C8").Value
'determines which variable to calculate from "Buoyancy Database" based on user defined variables
Sheets("Buoyancy Database").Select
If bow_d = "" Then
GoTo 100
ElseIf transom_d = "" Then
GoTo 110
ElseIf Weight = "" Then
GoTo 120
Else: MsgBox ("Error, all 3 inputs defined. Program will stop executing")
GoTo 200
End If
'determines unkown variable from user defined variables
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APPENDIX X: CENTER OF GRAVITY SOFTWARE
''if bow_d is undefined
100
Range("Z30").Select
col_offset = 2
Do Until Selection.Value >= transom_d
Selection.Offset(0, 1).Select
col_offset = col_offset + 1
If Selection.Value = "" Then
MsgBox ("Error, program will stop executing (100)")
GoTo 200
End If
Loop
'''selects transom depths for interpolation used to determine W1 and W2
transom_d2 = Selection.Offset(0, 0).Value
transom_d1 = Selection.Offset(0, -1).Value
Selection.End(xlUp).Select
Do Until Selection.Value >= Weight
Selection.Offset(-1, 0).Select
Loop
'''defines variables to interpolate for W1 and W2
W11 = Selection.Offset(0, -1).Value
W12 = Selection.Offset(0, 0).Value
W21 = Selection.Offset(1, -1).Value
W22 = Selection.Offset(1, 0).Value
'''interpolates for W1 and W2
W2 = ((transom_d - transom_d1) / (transom_d2 - transom_d1)) * (W12 - W11) + W11
W1 = ((transom_d - transom_d1) / (transom_d2 - transom_d1)) * (W22 - W21) + W21
bow_d1 = Selection.Offset(1, -col_offset).Value
bow_d2 = Selection.Offset(0, -col_offset).Value
'''interpolates to solve for bow_d
bow_d = ((Weight - W1) / (W2 - W1)) * (bow_d2 - bow_d1) + bow_d1
If W12 = "" Or W21 = "" Then
MsgBox ("Values out of range. Program will s top executing. Please check input values with 'Buoyancy
Database' sheet (100).")
GoTo 200
End If
GoTo 130
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APPENDIX X: CENTER OF GRAVITY SOFTWARE
'if transom_d is undefined
110
Range("X28").Select
row_offset = 2
Do Until Selection.Value >= bow_d
Selection.Offset(-1, 0).Select
row_offset = row_offset + 1
If Selection.Value = "" Then
MsgBox ("Error, program will stop executing (110)")
GoTo 200
End If
Loop
'''selects bow heights for interpolation used to determine W1 and W2
bow_d2 = Selection.Offset(0, 0).Value
bow_d1 = Selection.Offset(1, 0).Value
Selection.End(xlToRight).Select
Do Until Selection.Value >= Weight
Selection.Offset(0, 1).Select
Loop
'''defines variables to interpolate for W1 and W2
W11 = Selection.Offset(0, -1).Value
W12 = Selection.Offset(0, 0).Value
W21 = Selection.Offset(1, -1).Value
W22 = Selection.Offset(1, 0).Value
'''interpolates for W1 and W2
W2 = ((bow_d - bow_d1) / (bow_d2 - bow_d1)) * (W12 - W22) + W22
W1 = ((bow_d - bow_d1) / (bow_d2 - bow_d1)) * (W11 - W21) + W21
'''defines values for interpolation
transom_d1 = Selection.Offset(row_offset, -1).Value
transom_d2 = Selection.Offset(row_offset, 0).Value
'''interpolates to solve for bow_d
transom_d = ((Weight - W1) / (W2 - W1)) * (transom_d2 - transom_d1) + transom_d1
If W12 = "" Or W21 = "" Then
MsgBox ("Values out of range. Program will stop executing. Please check input values with 'Buoyancy
Database' sheet. (110)")
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APPENDIX X: CENTER OF GRAVITY SOFTWARE
GoTo 200
End If
GoTo 130
'if weight is undefined
120
Range("Z30").Select
col_offset = 0
Do Until Selection.Value >= transom_d
Selection.Offset(0, 1).Select
col_offset = col_offset + 1
If Selection.Value = "" Then
MsgBox ("Error, program will stop executing (120)")
GoTo 200
End If
Loop
Range("X28").Select
row_offset = 0
Do Until Selection.Value >= bow_d
Selection.Offset(-1, 0).Select
row_offset = row_offset + 1
If Selection.Value = "" Then
MsgBox ("Error, program will stop executing (120)")
GoTo 200
End If
Loop
Range("Z28").Select
'''defines variables to interpolate for W1 and W2
W11 = Selection.Offset(-row_offset, col_offset - 1).Value
W12 = Selection.Offset(-row_offset, col_offset).Value
W21 = Selection.Offset(-row_offset + 1, col_offset - 1).Value
W22 = Selection.Offset(-row_offset + 1, col_offset).Value
bow_d1 = Selection.Offset(-row_offset, -2).Value
bow_d2 = Selection.Offset(-row_offset + 1, -2).Value
transom_d1 = Selection.Offset(2, col_offset - 1).Value
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Appendix 93
APPENDIX X: CENTER OF GRAVITY SOFTWARE
transom_d2 = Selection.Offset(2, col_offset).Value
'''interpolates for W1 and W2
W2 = ((bow_d - bow_d1) / (bow_d2 - bow_d1)) * (W22 - W12) + W12
W1 = ((bow_d - bow_d1) / (bow_d2 - bow_d1)) * (W21 - W11) + W11
'''interpolates for W
Weight = ((transom_d - transom_d1) / (transom_d2 - transom_d1)) * (W2 - W1) + W1
If W12 = "" Or W21 = "" Then
MsgBox ("Values out of range. Program will stop executing. Please check input values with 'Buoyancy
Database' sheet. (120)")
GoTo 200
End If
GoTo 130
'determines location of buoyant force
130
Range("Z59").Select
col_offset = 0
Do Until Selection.Value >= transom_d
Selection.Offset(0, 1).Select
col_offset = col_offset + 1
If Selection.Value = "" Then
MsgBox ("Error, program will stop executing (130)")
GoTo 200
End If
Loop
Range("X57").Select
row_offset = 0
Do Until Selection.Value >= bow_d
Selection.Offset(-1, 0).Select
row_offset = row_offset + 1
If Selection.Value = "" Then
MsgBox ("Error, program will stop executing (130)")
GoTo 200
End If
Loop
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Appendix 94
APPENDIX X: CENTER OF GRAVITY SOFTWARE
Range("Z57").Select
'''defines variables to interpolate for W1 and W2
W11 = Selection.Offset(-row_offset, col_offset - 1).Value
W12 = Selection.Offset(-row_offset, col_offset).Value
W21 = Selection.Offset(-row_offset + 1, col_offset - 1).Value
W22 = Selection.Offset(-row_offset + 1, col_offset).Value
bow_d1 = Selection.Offset(-row_offset, -2).Value
bow_d2 = Selection.Offset(-row_offset + 1, -2).Value
transom_d1 = Selection.Offset(2, col_offset - 1).Value
transom_d2 = Selection.Offset(2, col_offset).Value
'''interpolates for W1 and W2
W2 = ((bow_d - bow_d1) / (bow_d2 - bow_d1)) * (W22 - W12) + W12
W1 = ((bow_d - bow_d1) / (bow_d2 - bow_d1)) * (W21 - W11) + W11
'''interpolates for W
Weight_loc = ((transom_d - transom_d1) / (transom_d2 - transom_d1)) * (W2 - W1) + W1
If W12 = "" Or W21 = "" Then
MsgBox ("Values out of range. Program will stop executing. Please check input values with 'Buoyancy
Database' sheet. (130)")
GoTo 200
End If
'assigns values to sheet
Sheets(sht_name).Select
Range("C6").Value = bow_d
Range("C7").Value = transom_d
Range("C8").Value = Weight
Range("C11").Value = Weight_loc
200
'hides buoyancy database sheet
Sheets(sht_name).Select
Sheets("buoyancy Database").Visible = False
End Sub
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Appendix 95
APPENDIX X: CENTER OF GRAVITY SOFTWARE
Display Component Layout Now that we have developed the software which allows us
to calculate the buoyant force location for various loading conditions, we then further developed
our software so that we could then calculate the COG of the hull, deck, and all other loading
components during the Endurance event so that we could ensure that we load the boat so that our
COG matches with the buoyant force location of the optimal operating point (transom
submerged 3 in according to Jon Howland’s CFD work). Once the COG was calculated, we
further added the ability to display the component location to ensure that the location of all
components is viable.
Table X.3 shown below displays the
component weight and position which the
Table X.3. Display of user inputs for component
weights and locations and calculated COG
compared with the buoyant force location
user defines, along with the buoyant force
location determined by the “Search Database”
function, and calculates the location of the
COG based upon the user defined inputs for
component weights and locations. Figure X.3
is an image created by running the “Display
Component Layout” macro by entering the
following keystroke, “ctrl+shft+m”.
Figure X.3. Display of components created by running “Display Component Layout” when the buoyant
force location of the displaced water and COG location overlap for a transom depth of 3 in and a hull
weight of 500 lb.
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Appendix 96
APPENDIX X: CENTER OF GRAVITY SOFTWARE
Solar Boat Final Report 2013-14
Appendix 97
APPENDIX X: CENTER OF GRAVITY SOFTWARE
Solar Boat Final Report 2013-14
Appendix 98
APPENDIX Y: ELECTRONICS
APPENDIX Y: ELECTRICAL SYSTEMS
Figure 1. This is the schematic for the Master Instrumentation Card. On the far left side we have
a comm serial connection going to the battery controller circuit. The outputs are the Deadman,
12V, 24V, 36V, Motor, and instrument switches. For inputs we have PPT 3, PPT 2, PPT 1, and
the Battery 1, 2, and 3 voltages, along with the battery current and tachometer. On the Right
hand side we have the following outputs going to the CCC: PWM back up, Kill switch, PWM
select switch, Back-up PWM signal, Clock, Data line 50, Data Line 51, and slave select line and
12V to power the CCC. The upper left hand side of the circuit are the analog signals. The bottom
left is the circuit for the strain gauges.
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Appendix 99
APPENDIX Y: ELECTRONICS
Figure 2. PCB layout for the MIC. The board is 6 × 9.5 𝑖𝑛 and consists of the Data Acquisition
system and all of communications to the other boards.
Figure 3. This circuit is for the strain gauges. We can see the Wheatstone bridge on the far left
hand side of the figure. With the other voltage follower and diff amp circuits.
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Appendix 100
APPENDIX Y: ELECTRONICS
Figure 4. Basic structure for the switches on the MIC. When the switch is open the variable is a
logical high and low otherwise.
Figure 5. This is the circuit for the servo tester. The signal is read through a voltage follower,
giving it the ability to drive 4 motor controllers.
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Appendix 101
APPENDIX Y: ELECTRONICS
Figure 6. Quartus basic structure for the CPLD. The block diagram on the left hand side consists
of our 9 variables: Dead man, 12V, 24V, 36V, Motor, Inst, Auxiliary Charge, Charge/Being, and
End/Sprint. These states are output to the MIC and also fed into the switch logic block diagram
on the right hand side. These will drive the switches inside the BCB.
Table 1. This table consists of all 9 input variables plus a timer variable that is internal to the
CPLD that determines how long each pre-charge state waits. We then have the 15 states that are
determined by the four states. This can be seen in Table 2, where we can see how each state is
determined. The OFF state has no power going to any controllers of DAQ systems. The 12V idle
brings power to the motor, but doesn’t allow the motor controllers to run. 12V race bring power
to the motor controller and the driver can control speed by the pot. 24V race is the mode where
the driver can run the endurance motor in 12V. The 36V Idle and 36V race state is similar to the
12V system. Aux charging is the mode where the battery box is charging the other battery box,
where the being charged state is the opposite. The 5 pre-charge states use shunts to limit the
current in the system to protect the FET switches. The OFF w/ inst is the same as OFF, except
the MIC has power. The 24V discharge is for stepping down from 24V race to 12V race.
logic states for
BCC
variables
Solar Boat Final Report 2013-14
Deadman
D
12V
A
24V
B
36V
C
Motor
M
Appendix 102
APPENDIX Y: ELECTRONICS
Charge/Being
H
End/Sprint
E
Auxilary charge
X
Inst
I
Timer
t
States
A
B C D
OFF
0
0
0
0
12V Idle
0
0
0
1
12V Race
0
0
1
0
24V Race
0
0
1
1
36V Idle
0
1
0
0
36V Race
0
1
0
1
Aux charging
0
1
1
0
Aux begin
0
1
1
1
12V precharge
1
0
0
0
24V precharge
1
0
0
1
36V precharge
1
0
1
0
Aux charge pre-ch
1
0
1
1
Aux Being pre-ch
1
1
0
0
OFF w/ inst
1
1
0
1
24V discharge
1
1
1
0
charged
Table 2. These are the logic sentences for each switch. Note how each switch depends only on
the 4 state variables. We have a total of 29 switches in the BCB.
/A/C/D + AC + AD +/BCD + B/CD +
1
/AB/D
/A/C/D+AC+/BCD+BC/D+/AB/C+A/BD
2
/B/C+AD+/AC+ A/C
3
/A/B+AB+/B/C+BCD
4
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Appendix 103
APPENDIX Y: ELECTRONICS
/A/C/D+AC+/BCD+B/CD+/AB/D+/B/C/D
5
/A/C/D+AC+AD+B/CD+BC/D
6
/A/C/D+AC+AD+B/CD+BC/D
7
/AB + /C/D+A/BC
8
A + /B+C
9
/B+/C+D+A
10
/B+/C+/D
11
/A/B/C/D
12
/A/C+/AB+B/C+/C/D+A/BC
13
A+/B+C+/D
14
B+C+D
15
1
16
/A+/C+/D
17
/A+/B+C
18
/AB/C+/AB/D+A/BC
19
A/B/C/D
20
A/B/CD
21
A/BC/D
22
ACD
23
AB/C/D
24
ABC
25
/B/D+BD+/C
26
/C+AB+/AD+/B/D
28
/A+D+/BC
27
/A+D+C
28
/A+D+C
29
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Appendix 104
APPENDIX Y: ELECTRONICS
Figure 7. This is the schematic for the current controller circuit (CCC), We have the RTD
circuits to the right and the solid state relays for switching the PWM signals on the bottom left.
The same signals coming out from the MIC feed into the comm serial connector in the top right
corner.
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Appendix 105
APPENDIX Y: ELECTRONICS
Figure 8. This is the PCB layout for the Current controller circuit. We have the solid state relays
in the center right side of the board, with the Uno32 on the left side of the board. Note we will be
having 3 of these boards; two for endurance, 1 for sprint.
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Appendix 106
APPENDIX Z: POWER AND WEIGHT BUDGET
APPENDIX Z: POWER AND WEIGHT BUDGETS
This year we made significant improvements in weight and efficiency. The weight gains are
summarized in Table Z. Also, the power budgets for both the Sprint and Endurance events are
shown in Tables Z.2 and Z.3 respectively.
Table Z.1: Weight budget showing weight reductions achieved for the 2014
competition.
Components
Solar Array
Batteries
Sprint Drivetrain & Controllers
Endurance Drivetrain
Hull w/ Bulkheads
Driver
MPPT
Control Panel
Miscellaneous
Total
Weight Reduction (lb)
Weight Reduction
Solar Boat Final Report 2013-14
2013
Sprint
N/A
100
154
27
105
155
N/A
5
10
556
139
25%
Weight [lb]
2013
2014
2014
Endurance
Sprint
Endurance
55
N/A
42
68
100
100
154
70
70
27
24
24
105
53
53
155
155
155
12
N/A
4
5
5
5
10
10
10
591
417
463
128
22%
Appendix 107
APPENDIX Z: POWER AND WEIGHT BUDGET
Table Z.2: Power budget for Sprint event.
Value
Unit
(metric)
Variable Name
BATTERIES
Variable
Battery Impedance
Nominal Battery Voltage
Battery Voltage under load
Battery Current
Battery Power Gain
Battery Power Output
Batt_Z
Batt_N
Batt_VFL
Batt_I
Batt_Pgain
Batt_Pout
0.008
36
26.4
1200
31680
31680
C_e
C_V
C_I
C_Pgain
C_Pout
0.95
25.1
1200
-1584
30096
V
A
W
W
M_e
M_T
M_ω
M_Pgain
M_Pout
0.90
51.7
524
-3010
27086
N*m
rad/s
W
W
DT_e
DT_T
DT_omega
DT_Pgain
DT_Pout
0.98
50.7
524
-542
26545
N*m
rad/s
W
W
Prop_e
P_Thrust
P_v
Prop_Pgain
Prop_Pout
0.72
1145
N
60.1 km/hr
-7433
W
19112
W
Hull Drag
Hull Velocity
Hull Power Gain
Hull Power Output
H_Drag
H_v
Hull_Pgain
Hull_Pout
1145
N
60 km/hr
-19112
W
0
W
Denotes input value
Efficiencies
Solar Splash Sprint Event
Unit
Value
(US)
Comments
Governing Equation
Ω
V
V
A
W
W
Sprint batteries
Design to draw power at this current
Batt_Pgain=Batt_V*Batt_I
Batt_Pout=Batt_Pgain
CONTROLS
Controls Efficiency
Controls Voltage
Controls Current
Controls Power Gain
Controls Power Output
Assuming 95% efficiency
C_V=C_Pout/C_I
Assume current is the same as from batteries C_I=Batt_I
C_Pgain=C_Pout-Batt_Pout
C_Pout=Batt_Pout*C_e
MOTOR
Motor Efficiency
Motor Torque
Motor Angular Velocity
Motor Power Gain
Motor Power Output
per conversations w/ Neu Motors (12/03/13)
38 lbs*ft
5000 RPM design motor speed for 5000 at 26.4 V
M_T=M_Pout/M_ω
M_Pgain=M_Pout-C_Pout
M_Pout=C_Pout*M_e
LOWER GEAR UNIT
Drive Train Efficiency
Drive Train Torque
Drive Train Angular Velocity
Drive Train Power Gain
Drive Train Power Output
Assuming 98% efficiency
37 lbs*ft
5000 RPM
DT_T=Mot_T
DT_ω=DT_Pout/DT_T
GP_Pgain=DT_Pout-Mot_Pout
GB_Pout=Mot_Pout*DT_e
PROP
Prop Efficiency
Prop Thrust
Prop Velocity
Prop Power Gain
Prop Power Output
Assuming 70% efficiency
257 lb
37.4 MPH Desired goal speed
P_Thrust=Prop_Pout/(P_v*(1000/3600))
Prop_Pgain=Prop_Pout-DT_Pout
Prop_Pout=DT_Pout*Prop_e
HULL
Output
Power
Solar Boat Final Report 2013-14
257 lb
37.4 MPH
H_Thrust=P_Thrust
H_v=P_v
Hull_Pgain=Hull_Pout-Prop_Pout
All the power should be used
Represents power in the system directly after the given component
Appendix 108
APPENDIX Z: POWER AND WEIGHT BUDGET
Table Z.3: Power budget for Endurance event.
Solar Splash Endurance Event
Ouput Unit
Unit
Value Power (metric) Value (US)
Variable Name
SOLAR PANELS
Variable
PV Power Gain
PV Voltage
PV Current
PV Output Power
PEAK POWER TRACKER
MPPT Efficiency
PV_Pgain
PV_V
PV_I
PV_Pout
360
16
22.5
MPPT_e
0.94
MPPT Current
MPPT Voltage
MPPT Power Gain
MPPT Output Power
BATTERIES
Battery Voltage
Battery Current
Battery Power Gain
Battery Output Power
MOTOR CONTROLLER
MPPT_I
MPPT_V
MPPT_Pgain
MPPT_Pout
Controls Efficiency
Controls Voltage
Controls Current
Controls Power Gain
Controls Output Power
MOTOR
Batt_V
Batt_I
Batt_Pgain
Batt_Pout
C_e
C_V
C_I
C_Pgain
C_Pout
A
W
338.4
A
V
W
W
648
V
A
W
W
12
54
648
0.95
5
12.6
62.8
-42
Denotes Input Value
Efficiencies
H_Drag
H_v
Hull_Pgain
Hull_Pout
167
14
-673
MPPT_I=MPPT_Pout/MPPT_V
MPPT_V=Batt_V
MPPT_Pgain=MPPT_Pout - PV_Pout
MPPT_Pout =MPPT_e*PV_Pout
Two 12 V Endurance batteries in series
Based on available amp-hours in 2 hour race
Batt_Pgain =Batt_Pout
Batt_Pout=Batt_V*Batt_I
C_V=Batt_V
C_I=MPPT_I+Batt_I
C_Pgain=-(Batt_Pout+MPPT_Pout)+C_Pout
C_Pout=(Batt_Pout+MPPT_Pout)*C_e
N*m
rad/s
W
W
1.9487 lbs*ft
3000 RPM Motor designed most efficient at 4000 RPM
M_T=M_Pout/M_ω
M_n=GR*GB_n
M_Pgain=M_Pout-C_Pout
M_Pout=Cont_Pout*Mot_e
Assuming 95% efficiency
Gear box designed with 5:1 gear ratio
789
0.853
167
10.7
600
14.5
-116
Assuming 94% efficiency
Assuming current stays same from panels to
PPT
From testing @ 3000 RPM without the
gearbox got 75 %, but with the new motor
design we are saving 60-70 W which is a 10%
of our motor out put (70/703)
830
Prop_e
P_Thrust
P_Torque
P_ω
P_v
Prop_Pgain
Prop_Pout
PV_I=PV_Pgain/PV_V
PV_Pout=PV_Pgain
V
A
W
W
976.54
GB_e
GR
GB_T
GB_ω
GB_Pgain
GB_Pout
PV_Pgain=480W*(% of one sun conditions)
Assuming 99% efficiency because we are
saving the 40 W that is lost from the battery to
the controller
0.99
12.0
82.2
-9.864
0.85
2.6
314.2
-146
Governing Equation
V
28.2
12
-21.6
M_e
M_T
M_ω
M_Pgain
M_Pout
Assuming avg of 75% of one sun condition
max (Insolation data for Dayton OH in June)
W
360
Motor Efficiency
Motor Torque
Motor Angular Velocity
Motor Power Gain
Motor Output Power
GEAR BOX
Gear Box Efficiency
Gear Ratio
Gear Box Torque
Gear Box Angular Velocity
Gear Box Power Gain
Gear Box Power Output
PROP
Prop Efficiency
Prop Thrust
Prop Toruqe
Prop Angular Velocity
Prop Velocity
Prop Power Gain
Prop Output Power
HULL
Hull Drag
Hull Velocity
Hull Power Gain
Hull Power Output
Comments
N*m
rad/s
W
W
9.2566 lbs*ft
600 RPM Due to gear ratio
GB_T=GB_Pout/GB_omega
GB_Pgain=GB_Pout-Mot_Pout
GB_Pout=M_Pout*GB_e
Assuming 81% efficiency
N
N*m
RPM
km/hr
W
673
W
N
km/hr
W
0
W
Output
Power
Solar Boat Final Report 2013-14
37.584
lb
P_Thrust=Prop_Pout/(P_v*(1000/3600))
9 MPH Desired goal speed
Prop_Pgain=Prop_Pout-GB_Pout
Prop_Pout=GB_Pout*Prop_e
37.584 lb
9.0243 MPH
P_Thrust=Prop_Pout/(P_v*(1000/3600))
Prop_Pgain=Prop_Pout-GB_Pout
Represents power in the system directly after the given component
Appendix 109
APPENDIX AA: MONETARY BUDGET
APPENDIX AA: MONETARY BUDGET
Shown below in Tables AA.1 and 2 is the monetary budget for the 2013-2014 Solar Boat team.
Table AA.1: Monetary budget for 2013-2014 Solar Boat team.
Cost
Item
Date
Solar cells
Aluminum for Platen
Smart Bypass Diodes
Tabbing and Busbar Wire
Wood for panel rack
Screws for panel rack
High temp bagging materials
EVA
Sub-Total
Ceramic bearings
Rotor Shaft
Stator Housings
Stators and Rotors
End Bells
Centering Rings
Controllers
Solar Array
$900.00
$0
$900
$112.80
$0
$113
$76.00
$0
$76
$50.00
$50
$0
$55.08
$0
$55
$3.60
$0
$4
$500.00
$500
$0
$200.00
$200
$0
$1,897.48
$750.00
$1,147
Lightweight RC Sprint Motor & Drivetrain
3/17/2014
$186.00
$6
$180.00
$750.00
$750
$0.00
$2,300.00
$2,300
$0.00
$4,400.00
$2,900 $1,500.00
$770.00
$770
$0.00
$880.00
$880
$0.00
$2,020.00
$220 $1,800.00
2/3/2014
Sub-Total
MDF for prop
Total
2/14/2014
2/10/2014
2/19/2014
2/20/2014
3/7/2014
3/10/2014
4/10/2014
4/16/2014
Sub-Total
WD-40
Material
Donations/ &
Sponsorship
3/11/2014
Sub-Total
Solar Boat Final Report 2013-14
$11,306
$7,826
Endurance Motor
$4.38
$0.00
$4.38
Propellers
$32.54
$32.54
$0.00
$0
$0.00
Company
Everbright
Alro
Mouser Electronic
E Jordan Brookes Co.
Lowes
Best
Airtech (full donation, estimated costs)
Ortech (free shipping)
Alexander's Welding & Machine
CECO Machine & Tool
Neu Motors
In-house (Quoted by two shops)
In-house (Quoted by two shops)
Jeti (Esprit) Model
$0.00
$3,480
$4.38
$0.00
$4.38
$32.54
$0.00
$0.00
$32.54
Lowe's
Appendix 110
APPENDIX AA: MONETARY BUDGET
Table AA.2: Monetary budget for 2013-2014 Solar Boat team continued
Lightweight Hull and Deck Manufacture
Material orders for testing from Soller
Composites
Dropcloths and vinegar
Wood for table and acetone
Infusion grade PP honeycomb core
from Plascore, 10-15 ft 2 of 0.25", 0.5",
and 1.0" thicknesses
materials for deck mold
Fiberglass for deck mold
Bagging Materials
Spray tac
Kevlar Shears
7, 51x102" pc of PN2 0.394" 1.5 pcf
honeycomb
Fabric rack materials (strut channel,
casters, etc.)
Acetone
conduit for fabric rack
Resin and hardener (12 gal infures, 5
gal infucure, 1 gal FAST
Kevlar fabric for boat
date
Fiberglass for intercore bonding
date
kevlar shears and other supplies
6, 46x108" pc. PN2 0.472" 1.8 pcf
honeycomb
2, 46x108" pc. PN2 1.250" 1.8 pcf
honeycomb
gel coat
11/1/2013
$428.04
$33.00
$395.04
Soller Composites (free shipping)
11/2/2013
11/2/2013
$14.82
$38.87
$0.00
$0.00
$14.82
$38.87
Walmart
11/8/2013
$200.00
$200.00
$0.00
Plascore (full donation)
1/20/2014
1/20/2014
2/10/2014
2/12/2014
2/14/2014
$115.59
$56.45
$3,000.00
$29.95
$30.00
$0.00
$0.00
$3,000.00
$0.00
$0.00
$115.59
$56.45
$0.00
$29.95
$30.00
2/14/2014
$1,000.00
$972.09
2/18/2014
$261.56
$0.00
$261.56
McMaster-Carr
2/20/2014
2/25/2014
$16.99
$42.73
$0.00
$0.00
$16.99
$42.73
Lowe's
2/27/2014
$2,510.51
$2,510.51
$961.90
$100.00
$861.90
3/15/2014
$135.00
$50.89
$0.00
$0.00
$135.00
$50.89
4/8/2014
$1,797.30
$1,797.30
$0.00 Plascore (Cedarville paid shipping only)
4/8/2014
$1,244
$1,244
$0.00 Plascore (Cedarville paid shipping only)
$260
$0
Sub-Total
10 strain gages
3/19/2014
$12,194
Hull Drag
$146
1/10/2014
$146.10
$0.00
Competition/Travel
$400.00
$0.00
Sub-Total
Entry fee
Sub-Total
TOTAL
Solar Boat Final Report 2013-14
$9,856
$0
$400.00
$0.00
Team Total
$25,981
$18,432
Lowe's
Lowe's
Fiberglast
Airtech (full donation, estimated costs)
Lowe's
Amazon
$27.91 Plascore (Cedarville paid shipping only)
Lowe's
$0.00 Endurance Technologies (full donation)
Soller Composites (free shipping &
discount)
ACP Composites
JMS & Northern Tool&Equipment
$260.00
$0.00
$2,338
JMS through Interplastic
$146.10
$0.00
$0.00
$146.10
Hottinger Baldwin Measurements Inc.
$400.00
$0.00
$0.00
$400.00
Solar Splash
$7,548
Appendix 111
APPENDIX AB: PROJECT MANAGEMENT
APPENDIX AB: PROJECT MANAGEMENT
Solar Boat Final Report 2013-14
Appendix 112
APPENDIX AB: PROJECT MANAGEMENT
Solar Boat Final Report 2013-14
Appendix 113
APPENDIX AB: PROJECT MANAGEMENT
Solar Boat Final Report 2013-14
Appendix 114
APPENDIX AB: PROJECT MANAGEMENT
Solar Boat Final Report 2013-14
Appendix 115