1998 – 99 NCDA
Final Design Report
Team 1:
Hovercraft
April 25, 1999
Brandon Fichera
B. Sean Gallagher
Gregory Pease
David Rabeno
Sponsor: Dr. Stephanie Wright
Delaware Aerospace Academy
Advisor:
Dr. Michael Keefe
Table of Contents
Pg. #
I.
SUMMARY
2
II.
INTRODUCTION
3
III.
CUSTOMERS/WANTS/CONSTRAINTS
4
IV.
BENCHMARKING
6
V.
METRICS
8
VI.
CONCEPT GENERATION
9
VII. CONCEPT SELECTION
12
VIII. FABRICATION AND ASSEMBLY
15
IX.
TESTING
17
X.
RE-DESIGN/SUGGESTED MODIFICATIONS
18
XI.
CONCLUSION
19
XII. BUDGET
20
XIII. APPENDICES
21
A. Shapes of Footprint and Sample Calculation
B. Educational Poster
C. Laboratory Experiment
D. Theoretical Work and Graphs
E. Hovercraft Safety and Operations Manual
F. Engineering Drawings
1
SUMMARY:
The purpose of this report is to present a detailed explanation of the work and thought
processes that are our senior design project. Presented here is the final design concept including
background and its complete history.
In defining the actual project, it was important to determine all the people that could use
our hovercraft. Once the customers were established, we had to take into account their role in the
project and to determine their specific wants. Once this list of customers and wants were
developed, the wants were evaluated with respect to customer importance. This was done so that
we were better able to prioritize our efforts.
Benchmarking was performed to learn more about hovercraft principles and operation.
Benchmarking was also used to develop yardsticks for measuring the quality of our design
concepts. These yardsticks became metrics and were how we compared our different concept
ideas.
Before intelligent discussion of ideas could be undertaken, further research was needed.
This research consisted of the derivation of relevant equations, discussion with experts and trips
to libraries. This deepened the understanding of the mechanics behind the problem.
After benchmarking and research, brainstorming sessions were held to generate concepts
as to how the problem could be solved. During these brainstorming sessions, all ideas were
considered to be valid, no matter how absurd they might seem. All manner of footprint,
educational, fun, lift and thrust possibilities were considered.
Once the ideas were developed, they were compared to wants and constraints via the
metrics. After which, some where discarded, some were kept, and some were combined to
produce a cohesive design concept that we believe to be the best solution according to the
specific problem. The concept selected presents a complete idea for our solution to the problem.
2
INTRODUCTION:
Dr. Stephanie Wright, president of the Delaware Aerospace Academy (DAA), has
sponsored senior design projects for the past few years. The DAA specializes in educating
children about the technology involved in the space program. In teaching, they hope to raise an
interest in the United States Space Program by presenting relatively new and interesting
technology that has yet to be widely distributed. This year, Dr. Wright desires a hovercraft to be
used at the DAA technical camps by students of grades 7 – 9. The hovercraft is to float on a
cushion of air and will be used to simulate exploration of a new planet and will also teach certain
scientific principles to the students. After discussing the scope of the project with Dr. Wright
and other customers, we formed a mission statement, which included our own goals for the
design. The statement reads as follows:
To design a two person hovercraft for the DAA that will demonstrate the relevant
scientific principles involved, simulate planetary exploration, interest children in
the space program, and provide a fun, safe and educational environment for
everyone involved.
The craft will be used as an educational tool to teach scientific principles to children in
high school and junior high demonstrations. By utilizing a two-pilot operating system, it teaches
teamwork and cooperation. Since hovercrafts are not very widespread, a vehicle that actually
floats on a cushion of air should especially intrigue the children. Allowing the children to pilot
the craft, we believe, will make the experience fun.
3
CUSTOMERS/WANTS/CONSTRAINTS:
A customer is anyone that would have a substantial interest in the final prototype or
design. After talking with our sponsor and considering all people that could possibly play a role
in the design and final product, we came up with a ranked list of customers. The list is as follows
(in order of importance):
1)
2)
3)
4)
5)
6)
7)
8)
Dr. Stephanie Wright – DAA
Eric Rabeno – Junior High Student
Bethany Fichera - High School Student
Martin Rabeno – High School Teacher
Selina DiCiccio – Junior High Teacher
Ron Perkins – Educational Innovations
Dr. Robert Bloom – Aerospace Engineer (DAA)
Dr. Mark Elison - Principal of Junior High and High School
Dr. Wright was our most important customer because her organization sponsored the
project, provided the funds and will be the primary user of the hovercraft for demonstrations.
Students were our next most important customers because they are the people that should
benefit the most from the project. We needed the students’ input to understand how to let them
have fun while being educated.
In addition to students, other members of the educational community that were our
customers are their teachers. After we designed our concept, we had to make sure that high
school and junior high school teachers understood what we were trying to accomplish. Since
they are professional educators, their input as to how to make the design educational was
essential to our success.
Educational Innovations supplies lab and science equipment to schools which teachers
use to explain certain scientific principles to children. Mr. Perkins, company representative, is
one of our customers because of the insight he can provide as to what works well and what
doesn’t work well as an educational tool. In addition, he provides help with the educational
aspect of the mission.
The school system superintendents and principals were included as customers because
they are concerned with the education of their students. As well as education, their knowledge of
what safety considerations were needed for the craft to be considered safe in a school
environment proved invaluable.
4
After talking with these customers and discussing each of their wants from the project, a
list of wants was developed and SSD was used to rank them. The wants are listed below.
1)
2)
3)
4)
5)
6)
7)
8)
9)
Demonstrate scientific principles
Make it fun
Have it look ‘cool’
Maneuverability
Reliability
Transportability
Reproducibility
Durability
Affordability
We were fortunate in our design process to be able to meet our customers’ wants without
having to make many trade-offs. The trade-offs we made were slight. For example, to make the
craft cool looking we needed to spend more money, decreasing the craft’s affordability.
Constraints dictated how well the wants were satisfied. The constraints are listed as
follows:
1)
2)
3)
4)
Operation (The hovercraft must hover)
Allowable Funds ($2000)
Size of door in Room 109 Spencer Lab (4.5’ X 6.3’)
Number of pilots (must be able to fit two)
5
BENCHMARKING (System and Functional):
Benchmarking, a process that continued throughout the duration of the project has proven
to be very valuable in the design of the hovercraft. Initial benchmarking was done on a variety of
overall hovercraft systems as well as components in order to determine best practices.
Initial benchmarking determined that there was not a complete system on the market that
satisfied the wants of our specific design problem. The system closest to what is desired is the
Triflyer Hovercraft from Robert Q. Riley Enterprises. The Triflyer was able to handle a
maximum payload of 800 lbs. (3 people), traveled 75 mph and was 12' x 6'. This design satisfied
the weight requirement, but was extremely overpowered for what we were looking for. Since this
system was very close to the desired goal, plans for the Triflyer were ordered studied for concept
and component design. This gave insight as to industry standards for such components as
steering, skirt design and typical mounting points for engines and fans. Other benchmarks are
shown in the table below.
Table1: Benchmarking
Robert Q. Riley Enterprises (Triflyer)
Plans for hovercraft. Best practice
Robert Q. Riley Enterprises (Pegasus)
Round hovercraft plans, max weight 150 lbs.
Design has no viable propulsion method.
Universal Hovercraft (Kits and components)
Kits offered are smaller than desired. Cost well
above budget.
Offer fans for lift and thrust. Staff very helpful.
Hoverclub of America
Published a variety of articles describing principles
of hovercraft such as lift, thrust, and design tips.
Hovertech
Levitation using electromagnets
Universal hovercraft supply’s hovercraft kits and components such as fans for personal
hovercrafts. Our fan and hub assemblies for lift and thrust were purchased from this company, as
well as material for the skirt (neoprene coated nylon).
Functional Benchmarking was done on a variety of systems and ideas in order to generate
concepts and determine components for the design. Also, functional benchmarking became
important in the educational and recreational aspect of our project. We performed some searches
that would help us become familiar with different teaching methods. Six Flags Great Adventure
and the Smithsonian Air and Space Museum were studied in order to come up with a way to
6
satisfy our wants of educational and fun. Six Flags uses speed, sounds, colors, and fast
movement in order to make their rides fun for children and adults of all ages. The Air and Space
museum takes a more reserved approach towards fun and learning. They use videos, descriptive
posters and/or exhibitions, and rely on some hands on demonstrations to facilitate learning and
fun.
As far as the operational aspect of the hovercraft is concerned, components such as
engines (Briggs and Stratton, Tecumseh, Honda), were researched and priced form a variety of
distributors, such as Grainger and Northern Tool Supply. Fans, skirt material, wood and other
building materials were also investigated to get a better idea of what needs to be ordered, their
costs, and the lead time associated with each as well as usefulness in fulfilling the design
requirements.
7
METRICS:
During the benchmarking process, notes were taken with regard to operation on some of
the important items that are normally measured in order to estimate the quality of a hovercraft
design. Our design can not be compared to our competitor’s best practices unless a common
yardstick is developed upon which to base the evaluation. By observing what items the
competitors measured to determine quality as well as conversing with our customers, we
developed a list of metrics for our wants. Once the metrics were established, target values were
assigned to them based on Dr. Wright’s wants and the competitor’s values. The list of metrics
and their corresponding target values is shown below.
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
Number of Principles Taught – 3
Performance on a lab experiment (to be explained) - average score = 80%
Object Clearance (from bottom of craft to ground) - 6”
Skirt to Ground Clearance - 0.5”
Speed of vehicle – 5 - 10 mph
Acceleration of vehicle – 1mph/s
Directions of Travel – 360 degrees (all horizontal directions)
Travel Range – unlimited (limited by fuel capacity alone)
Turning Radius – 15 m
Fuel Efficiency/Capacity – 3.5 continuous hours.
Cost - $2000 max
Weight - 1000 lbs.
8
CONCEPT GENERATION:
This specific design project is unique in that there are three main goals of this project that
are very closely tied to each other: education, fun and functionality. These three requirements
lead to a very unique process of concept generation.
As a result of brainstorming and benchmarking, several ideas were obtained that would
satisfy the specific needs of education, fun, and operation individually. Once a few concept ideas
for each requirement were obtained, the next stage was to try and combine the most feasible
ideas corresponding to each aspect into a cohesive concept that would satisfy all parts of the
problem best according to our metrics and result in a well balanced concept.
Because this project is geared towards children, we looked to two proven leaders in the
fields of education and fun: museums and amusement parks. For best practices, the Smithsonian
Air and Space Museum and Six Flags Adventure Parks were chosen. The “Smithsonian
Approach” is superb for learning. They are internationally known as providing excellent exhibits
in their museums. Their methods of education are especially helpful since they additionally
incorporate fun in their exhibits through hands on experiences. The “Amusement Park
Approach” dealt strictly with fun by making rides bigger and faster with lots of noises and
colors. Using these techniques, amusement parks are able to keep people entertained.
The third part of concept generation, and the one that best utilized the engineering tools
we’ve acquired over the past four years, was the design for the prototype hovercraft. Fans,
magnets, and suspension systems were researched for ways of lifting the hovercraft. One concept
was to have magnets on the ground along with opposing ones on the craft. The magnets would
repel each other and lift the craft. Suspension systems could be used to move the hovercraft
around while suspending it above the ground, using a cable attached to the frame. Fans are the
traditional and most common method for providing the lift forces.
Power generation concepts using liquid fuel, batteries and fuel cells were studied. Fuel
cells are costly but provide a great deal of clean energy. Batteries are an inexpensive but are
heavy. Liquid fuels are abundant, lightweight and inexpensive.
One aspect that goes along in designing the lift system is the type of skirt to be used
around the bottom to keep air trapped under the craft. Two concepts were generated for the skirt
design. A bag skirt, which is a lot like an inflated inner tube under the craft, or a C skirt, which is
a piece of material draped along the craft much like a table cloth.
9
Shape is another important consideration in concept generation. Shape determines the
surface area. The pressure multiplied by the bottom surface area limits the lifting weight. A
number of shapes were looked at when considering the design of the footprint. The main concern
with shape would be in obtaining one so that the area under the craft allowed for a relatively
small air pressure. Several shapes considered are included in Appendix A along with a sample
pressure calculation.
Thrust is another area where concepts could differ. Benchmarking showed that a fan
system used for thrust seemed to be the best practice. Other possible thrust methods would be to
have the craft pulled/pushed by another person, or using some sort of jet propulsion.
Maneuverability could be done with a rudder system, or by having multiple fans that
rotate to change the direction of airflow. The second of these options would be more expensive
and also difficult to construct so that high school children would be able to control it.
Pilot positioning was also a concern. The pilots could be positioned one behind the other
or side by side. The craft needs to hover almost perfectly level so that a consistent gap height is
achieved. The positioning of the pilots is important in this aspect. Placing the pilots front to back
would make it hard to design the craft so that the two pilots could cooperate on steering and
propulsion. Positioning the pilots side by side would allow us to place all control items on a
“dashboard” in the front of the craft that would be easily accessible by either pilot. The following
drawing shows the differences that an unbalanced craft would exhibit as opposed to a level craft.
10
The air rushing out from under the craft in the second drawing would detract from the overall
hovering capability of the craft.
11
CONCEPT SELECTION:
With all these concepts possible as a means of satisfying each of the three aspects of our
project, it became a matter of studying our metrics and constraints. These would be used to pick
a specific concept for each of recreation, fun, and operation. After these components were
picked, it was necessary to figure out how to combine each of the three concepts into one
complete design for a fun, educational and working hovercraft.
Arriving at a harmonious union of education, fun, and operation proved to be easy to
accomplish. The solution combines both the methods of the Smithsonian and Six Flags. Included
in this approach is a poster that students will be able to look at that discusses what hovercrafts
can be used for, how they relate to the space program, and also the principles our prototype relies
on for successful operation (slides are located in Appendix B). Also included is a lab experiment
to be performed on the concept of lift (located in Appendix C) which will give the children the
hands on aspect of the science that the Smithsonian Institute does so well. Finally, piloting the
actual hovercraft will allow the children to see everything the first two items has taught them.
They will be able to take the information from the poster and experiment and apply it to a
working hovercraft that will provide plenty of excitement.
It is felt that students will learn the most by reading the poster and performing the lab
before operating the hovercraft. The students will build a simple hovercraft themselves in the
short lab. The lab is designed to show how lifting force, air pressure, and footprint sizes are
related. After completing these steps, students will be allowed to ride the hovercraft with a better
understanding of its working principles.
To determine the final result of the lab and poster, several iterations of each have been
done. The poster and model were brought into a classroom where verbal feedback and reactions
from the students helped us to make the necessary changes to both items. All students crowded
around the model from the lab and wanted to touch it and push it. Several students asked how to
build it and wanted to try making a miniature model on their own time. Their reactions and the
resulting iterations increased the amount of understanding by the students, which allowed the
presentation to educate more effectively. Based on the results of talking to several students and
their teacher, the presentation of important concepts has been altered until optimal understanding
was obtained.
12
The final hovercraft is a 10-ft long and 6-ft wide rectangle. Drawings are shown in
Appendix D. This shape was picked because of the footprint, it was the easiest shape to
manufacture of the shapes considered and it optimized the area underneath the craft for the lift
system.
The lifting is done with a single fan located in the front of hovercraft. A fan system was
chosen over a magnetic system due to the cost restriction on the project. In addition, the
magnetic system did not allow unlimited planar range. It also did not simulate exploration as the
magnets would already have to be placed in the area prior to that area being explored.
Suspension systems were eliminated for one major reason: the craft would not be hovering.
Thus, we chose the fan systems as the best of our options based on the wants and metrics and the
“hovering” constraint.
Gas power was chosen due to the cost and power output per pound of a gas engine
compared to electric. An 8 HP gas engine costs about $400 and weighs about 60 lbs. The
batteries to operate an equivalent electric motor weigh twice as much and replacement batteries
are expensive. Fuel cells were eliminated on cost alone. A fuel cell to power an electric motor
costs in the tens of thousands of dollars.
We determined the lift fan diameter, after consulting with Universal Hovercraft.
According to their calculations, the fan needed to lift our weight with an 8 HP motor is 26" in
diameter and has four blades. The lift engine is mounted in the front of the craft above the fan
(the engine will be a vertical shaft engine). The location for the engine was determined by
looking at competitors best practices.
A bag skirt was chosen for the design for two reasons. Bag skirts allow for a more
complex shape of a craft. The C skirt is a very unstable system because it has the tendency to
flap out, releasing air and lowering the craft. In addition, objects passing under the craft have a
tendency to be picked up by the skirt. This increases the possibility of ripping the skirt, the
weight (if the skirt carries the object) and, if the object is heavy enough, the possibility that the
craft will abruptly stop.
In the final design, we decided to position the pilots side by side. If the pilots were
positioned front to back, the pilot’s compartment would have to be longer. With a design longer
than the current one, the prototype would not be able to leave the Senior Design Room.
13
Balancing any difference in weight between the pilots can be compensated with weights under
the seat.
Another fan and a 3.5 HP horizontal shaft motor on the back of the hovercraft will
accomplish the thrust for the craft according to our theoretical calculations. This is not only
industry standard, but it also the best practice for what we seek.
Maneuvering of the craft is done by a rudder system attached to the rear of the thrust fan
assembly. The two rudders will be coupled and the steering system for the rudders is assembled
so that the steering “column” will be on the dashboard and accessible by either pilot. This will
allow for teamwork as both the steering and the lift throttle will be placed on the “dashboard”
allowing each pilot to operate one of the two systems.
14
FABRICATION AND ASSEMBLY:
The final development and fabrication times



Engineering Concept Development
110 hours
Fabrication
610 hours
Redesign and Modification
20 hours
TOTAL: 740 hours
The frame of the hovercraft is a rib structure designed to be lightweight and strong at the
same time. The ribs were constructed with 1” x 2” pine. A template was laid out on a piece of
plywood and the pine was cut and made into kits for each rib. The template was then used to
construct the ribs and ensure all ribs came out to be the same dimensions. The template was then
modified to allow for the construction of the second type of rib used in the driver compartment
and also the third type used at both ends.
Once all the ribs were constructed, the next step was to hang the ribs on two 2” x 4” x 10’
stringers (see drawing). The ribs were spaced out according to the drawings and attached to
these stringers.
Next, the 10’ x 1” x 2” stringers were put in to place.
This was followed by the installment of the rest of the members used for support around
the lift and thrust fans.
The craft was then turned so the bottom was face up and ¼” plywood was used to cover
the entire bottom. One piece contained a 30” diameter hole, cut on a CNC router for accuracy, to
accommodate the lift duct. Bondo was then applied at the seams to help make the bottom
airtight. Once this was done the wood was sealed with a polyester resin and the skids were
installed.
Upon the completion of the bottom, the craft was turned right side up. The crew
compartment’s bottom was covered with ¼” plywood and 1/8” Luan applied over the rest of the
craft. Bodywork was done with joint compound and Bondo to even out the body and give it a
more professional appearance.
15
The skirt was fabricated using the material obtained from Universal Hovercraft. The
material was cut and then sewn together using Kevlar thread and super-glue to create the corners.
Sheet metal screws were used to attach the skirt to the craft. A small flap of material was placed
over a portion of the lift duct to direct some air from the lift fan into the bag skirt.
The lift duct was created using a roll of aluminum flashing. The aluminum was wrapped
four times and machine screws were used to help it keep its shape. This duct was then placed in
the two 30” holes and ran through the entire craft.
The lift engine was mounted to a composite plate made of vinyl-ester resin, 3 layers of
24oz woven roving E-glass, a ¼” balsa core and then 3 more layers of E-glass. This was then
mounted to two pieces of angle iron used to span the lift duct. The fan was mounted to the engine
shaft using the hub provided by Universal Hovercraft and a 1in. diameter split taper bushing. At
this point the first lift test was successfully conducted with one person in the craft.
A windshield was constructed next using pultruded fiberglass box beams and a piece of
polycarbonate. This was attached with four bolts keeping in mind it would need to be removed
in order to remove the craft from the room. Two boat seats were installed side by side in the
crew compartment for the pilots. Also, the controls for the lift and thrust fans and the steering
system were mounted on a “dashboard” so that the two pilots could work together to operate the
three systems.
In order to allow the craft to be removed from the building, the thrust housing was
required to be removable. The box to contain the fan was made with 1” x 6” pine. A ¼” x ¼”
protective screen was placed over the outer opening. All of this was attached to a piece of ¼”
plywood. This assembly is bolted to the craft to allow the assembly to be removable (see
drawings). The thrust motor was placed above the back of the hovercraft on a box 8” high to
allow the fan to be centered in the housing. The two rudders were made from 1” Styrofoam. The
steering is done by sliding the handle in the “dashboard” from right to left depending on the
desired direction of travel. This is attached to the rudders using ¼” nylon cord.
The entire craft was next painted with a semi-gloss black paint. After this was complete,
yellow caution labeling was applied to areas that were dangerous. The construction was
completed with the mounting of a fire extinguisher. After the hovercraft is removed from the
senior design room and before the craft is delivered, safety screens will be placed over the front
lift fan and also the remaining portion of the thrust assembly.
16
TESTING (Lift System):
1) Hovering Capability
Weight Skirt to ground clearance
Just Craft Trial 1 Trial 2 Trial 3
50 lbs.
6"
6"
6"
100 lbs. 6"
6"
6"
150 lbs. 5.8"
5.5"
5.75"
200 lbs. 5.75" 5.6"
5.5"
250 lbs. 5"
5.25" 5"
300 lbs. 4.25" 4.33" 4.2"
4) Time it takes craft to settle after
shutting engine off
Average
6"
6"
5.68
5.62
5.08
4.26
2) Approx. angle of hover
We found that getting the craft to hover flat is just a matter
of balancing it. With two pilots of relatively equal weight,
the craft hovers almost exactly horizontal.
Time
Trial #
1 pilot
2 pilots
1
1 sec. 1 sec.
2
1 sec. 1 sec.
3
1 sec. 1 sec.
4
1 sec. 1 sec.
5
1 sec. 1 sec.
* We found that as soon as the engine
is cut, the craft settles down on its
skids pretty quickly. It is not so sudden
as to deter from the safety of the craft
5) Stability
Height of Oscillations
Small to nothing. With the throttle in one position,
3) Amount of time from when the engine
starts until it is hovering
Time
Trial #
1
2
3
4
5
1 pilot
2 sec.
3.5 sec.
4 sec.
2.5 sec.
2.5 sec.
2 pilots
3 sec.
3.5 sec.
2.5 sec.
2 sec.
3 sec.
* Basically, the time it takes the craft fully rise
depends on how the pilot operates the throttle.
the craft will hover at a constant height
6) Does the craft hover in place or does
it tend to go in a certain direction?
This depends on two factors: wind and terrain.
On perfectly flat ground with no wind, the craft
hovers in place. With hills and wind, the craft
tends to move.
7) Do we have to adjust the skirt each time
we start it or will it hover by simply starting
the fan?
The hovercraft will rest on the skids so that
the skirt does not have to be adjusted each
Thrust:
Since the thrust fan was not the proper kind, the thrust force needed to move the craft was
tested using a scale to measure the force required to move it. It was found that the calculations
for the thrust were indeed accurate. With 300lbs in addition to the empty weight of the craft,
60lbs of force was required to move forward and only 15lbs of force was required to turn.
17
RE-DESIGN/SUGGESTED MODIFICATIONS:
During the testing of the lift system it was noticed that the lift fan had risen up the shaft
and was rubbing against the engine support plate. To prevent this from happening again a 1”
bronze collar was placed on the shaft above the hub for the fan. This will prevent the hub from
hitting the engine plate again. A new engine plate was also fabricated to replace the damaged
plate.
The thrust fan, which had been donated to the project, turned out to be pitched wrong for
the motor set-up. The fan needed to push air when turned clockwise, but instead the fan pulled
air. To rectify this, a new fan had to be ordered with the correct pitch that would work based
mainly upon our theoretical calculations and also on our testing results using the scale.
Depending on the weight of the pilots, ballast must be added to compensate. This can be
changed during operation to allow the craft to float level. Water jugs can be placed in the front
of the craft to allow for extra weight.
18
CONCLUSION:
The task of constructing a prototype hovercraft according to Dr. Stephanie Wright’s
wants that satisfied our mission statement has proven to be a successful one. With only one
minor setback, we satisfied all of our wants according to the problem definition. The first three
wants (demonstrate scientific principles, fun, and cool looking) were satisfied very well
according to the feedback received from our sponsor, the students, and the teachers we talked to.
The most significant accomplishment of the project was being able to theoretically design a
mechanism for lifting the hovercraft to a desired height according to our desired weight and then
having the assembly work almost exactly how we designed it. The desired height of hovering
with two children (from base of craft to ground) was listed in the metrics as 6”. Upon testing of
the lift system, it was found that with the equivalent weight of two students, the craft hovered at
a height of 5.25”. This is very close to our target value.
The only setback came with the discovery that the fan we were going to use for thrust
force was pitched the wrong way. This combined with the fact that the thrust engine did not work
initially and had to be repaired did not leave enough time before the final presentation to have a
new fan delivered and the thrust system tested using the fan/motor combination. However, to
compensate for this, we used scales to test the amount of actual thrust force needed to move the
craft and to turn the craft. We discovered during these tests that our theoretical calculations for
thrust force were accurate and also found out that it would only take 15 lbs. of force to turn the
craft. This number coincides well with the theoretical calculations also. With these test results,
we were able to order a new thrust fan that will satisfy the thrust requirements and finalize the
project. With the completion of the thrust system, we will have satisfied all the wants given to us
by the customers.
The one concern when starting the project was the relatively small budget of $2,000
dollars. After careful benchmarking and research, we were able to come up with and construct a
complete solution for $1779.36, which is under budget.
Before we began working on the project, we all thought it sounded pretty interesting.
Only now that it is complete can we fathom how important and educational the whole process
has been. We can now look back on all our initial expectations and worries take pride in the fact
that we were able to design a complete solution to the problem assigned.
19
BUDGET:
The final budget report for the project is as follows:





Materials (Wood, Hardware) Lift fan, Skirt, Hub 8hp Lift Engine Thrust Fan 3.5hp Thrust Engine TOTAL:
$ 734.45
$ 361.22
$ 358.70
$ 157.00
$ 167.99
$1779.36
The estimated cost for production of a similar craft is the Projected Production Cost and is as
follows:

Total Material Costs:
- $1779.36

Estimated Production Hours:
- 200 hours
- $25/hr

Projected Cost = $5000 + $1779.36 = $6779.36
20
Appendix A: Shapes of Footprint and Sample Calculation
Sample Calculation for rectangle:
Area = length x width = 10 x 6 = 60 ft2 = 8640 in2
Weight = 2000 lbs.
(Weight from metrics with a factor of safety of 2)
Cushion Pressure = Weight/Area = 2000 lbs./8640 in2 = 0.231 lbs./in2
21
Appendix B: Educational Poster
Double click on Title Screen to view
22
Appendix C: Lab
Demonstration of Lift System for AntiGravity Vehicles
Purpose:
It is important to understand the scientific principle of lift in any vehicle that is freefloating or built specifically to defy gravity. The purpose of this experiment is to learn about how
a free floating vehicle actually “defies” gravity. It will be important to understand the
relationship between surface area of the vehicle, the weight of the vehicle and the air pressure
developed between the vehicle and the ground. This experiment will provide the information
necessary to understand the concept of lift.
Theory and Background:
Anti-gravity vehicles have become an area of great interest recently. Some people build
them at home as a hobby much like go-carts. There are also important scientific uses for
hovercrafts and other free-floating vehicles. The present level of scientific technology is so
advanced that NASA and separate state space programs and space camps would have very
important uses for an anti-gravity hovercraft. One of the uses is to use a hovercraft to explore
unknown places on a planet. Astronauts that land on a planet for the first time would not be able
to completely know what the terrain is like before they land. Because of this fact, a vehicle that
hovers off of the ground is the best way to explore that planet in case it is not easy to drive a
vehicle with wheels. The Delaware Aerospace Academy will demonstrate a life size hovercraft
that was designed for the purpose of showing how planetary exploration would take place. By
performing this experiment before viewing the demonstration, you will better understand how
the hovercraft actually lifts off the ground and how it works. The equation that is important in
figuring out if a hovercraft will actually hover is F = (P) X (A). In this equation, F = weight of
the hovercraft plus passengers (the force needed to lift the hovercraft). A = the surface area on
the bottom of the hovercraft (in this experiment the hovercraft is a rectangle and its A = length X
width. And the P = air pressure between the hovercraft and the ground. Its units are pounds per
square inch. You will construct hovercrafts of different weight (F) and area (A) and find the air
pressure needed to cause lift.
23
Necessary Equipment:
- Two standard 3” computer cooling fans (12VDC, .13Amps, 1.60Watts)
- One 12 Volt DC battery
- Two pieces of polystyrene poster-board 9” X 16”
- Eight strips of pre-cut plastic (trash bag material)
- Four 16” strips, two 9” strips, and two 18” strips
- Masking Tape
- A set of small weights totaling about 4 lbs.
Procedure:
1) Using the piece of poster-board with the computer fans attached (holes will be precut
in the poster-board with computer fans taped into them), tape one 9” piece of plastic
to each shorter edge of the poster-board. Then, use the two 16” strips of plastic and
tape those to the longer edges of the poster-board. Turn the poster-board over and use
one piece of tape at each corner to attach the plastic strips as shown in figure 1 on the
next page.
2) Before you turn the fans on, you must make sure the hovercraft is right-side up and
all the loose ends of plastic are tucked under the craft. Then, hook the red wires on
the fans to the positive (+) terminal of the battery. Then hook the black wires to the
negative (-) terminal. Observe what happens. Does the hovercraft lift off the table? If
it lifts, try putting some small weights on the poster-board away from the fans. If it
lifts, write down the largest amount of weight it can hold up (and add this value to the
weight of the hovercraft which is 1 lb.). The area A = 16” X 9” = 144 inches squared.
With this weight (F) and area (A), use the equation F = P X A to calculate the air
pressure. If it does not lift at all, move on to the next part.
3) Take the pieces of plastic off and tape the other piece of poster board onto the first
one. Now use the two 18” pieces of plastic on the edges you used the 9” pieces on
before and put the two 16” pieces on the other two edges as in figure 2. Then tape the
corners as before and use the fans to try and lift the new set up. Again, add different
weights to the hovercraft away from the fans. Does this one lift? Does this hovercraft
lift better than the first one? Write down the largest amount of weight it can lift this
time (remember to add the weight of this craft which is 1.25 lbs.). The area for this
craft is A = 288 inches squared. Calculate the value of air pressure for this hovercraft.
4) Based on what you saw for the two hovercrafts, which one seemed to work better?
Which one had a lower value of air pressure (P)? What can you say about the
relationship between the value of P and how well the hovercraft works?
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FIGURE 1
Top View
Bottom View
FIGURE 2
Top View
25
Appendix D: Theoretical Work and Graphs
Equations Used And Derivation of Power Equation:
Conservation of Energy and Conservation of Mass from the fluid mechanics perspective
is used throughout.
P3 V 23
V 22

 gz 2 

 gz3

2

2
V 21
P 2 V 22

 gz1

 gz 2 ws
 2

2
P2
P1
Steady-Flow Energy Equation 1 – 2
Bernoulli’s Equation 2 – 3
26
ws 
From Energy Equation:
weight
A
From Bernoulli’s Equation: V3 
2P2


A  lw
m  Q
Other useful Equations:
Final Relevant Equations:
P
Wweight
A

Wweight
lw
Q  V3 Aperimeter  2(l  w)
2Wweight
lw
3
Wweight
 
W   w s m  2(l  w)
 (lw)3



Thrust Equations & Calculations:
F  Ma
W
M
go
W = 1000lbs. (from Metrics)
a = 1.5 ft/s2 (from Metrics)
go = 32.2 ft/s2 (from Metrics)
Thrust Force Required = 60lbs.
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Figure 1 : Gap Height = 1.0cm
Figure 2 : Gap Height = 1.5cm
Figure 3 : HP = 8
Figure 5 : HP = 6
Figure 4 : HP = 7
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APPENDIX E:
Hovercraft Safety and
Operations Manual
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Safety Suggestions:
Please use caution when operating or standing close to the hovercraft. It is
suggested that safety glasses and hearing protection be worn during operation for all
pilots and adult spotters. Please use in a flat open area with adult supervision at all
times. A fire extinguisher is located at the back right corner of the craft in the case of
an emergency.
The hovercraft’s direction can change depending on terrain, for this reason we
suggest that an adult stay close to the hovercraft and act as a spotter. Because of the
little force required to move the craft, an adult near the hovercraft can simply hold the
side of the hovercraft to steady its position and allow the pilots to recover. All
stopping mechanisms are located near the sides of the craft to allow the engines to be
shut down easily in the event of a problem.
Operation:
The craft is designed to hold two pilots: one to control the lift and throttle and
one to control the direction. These two pilots should be close to the same weight and
the total weight should be less than 300 lbs. for optimal performance.
Starting the hovercraft:
1) Enter the craft from the sides, stepping only on the panels labeled ‘step’.
2) Make sure both pilots are seated and familiar with the operation of the craft.
3) Do an inspection check of the craft including:
a) Both engines and fans
b) All screens. To be sure they are in place and secure.
c) The wiring to be sure all wires are connected.
d) The skirt for tears and holes.
4) Starting the thrust engine: Set the bottom lever to choke and the top lever to fast.
Pull the cord to start the engine, once started move the bottom lever to run and the
top to slow.
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5) Starting the lift engine: Pull the throttle one half inch from its base; then, turn the
key to the right. Once the engine starts to run, pull the throttle level up slightly.
Then adjust until you can here the engine run at its highest speed. Caution.
Pushing the throttle all the way forward will shut the engine off. Note: Turning the
key to the off position will always shut the engine off.
6) Once hovering set the thrust engine to desired speed (top lever).
7) Steering is accomplished through the moving of the rudder stick located in the
dash. Remember: Moving the rudder to the left will make the craft’s rear travel to
the right. Centering the controls will then move the craft it the desired direction.
This it also true for the reverse direction.
Shutting down the hovercraft:
1) Shut down thrust engine by moving the top lever to the stop position. Do not
move the lever to choke to shut the engine off.
2) Shut down the lift engine by turning the key to the off position (turning to the
left).
3) Once both the lift and thrust fans have stopped it is safe to exit the craft.
4) Exit the craft be standing and then stepping on the panel labeled “step”.
Gas and Oil:
Both the lift and thrust engines can be filled with regular unleaded gas.
Both the lift and thrust engines run on SAE 30 motor oil, which is available at most
auto-part stores and gas stations. Both gas and oil levels should be checked
frequently. Both engines should have their oil changed after the first 5hrs. of use.
Thereafter, follow the maintenance suggested in the manuals located at the end of this
document.
Maintenance:
A)
Tools possibly needed:
½" open ended wrench
½" socket drive
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Flat head screwdriver
Phillips head screwdriver
Staple Gun with staples
B)
Both the lift and thrust engine manuals are located at the end of this manual.
These contain the maintenance schedules and also a trouble-shooting guide for each
engine. If there are any problems with the engine that can not be solved by consulting
these manuals, contact Charlie’s Equipment Service at the below address.
Charlie’s Equipment Service
14-B2 Albe Drive
Newark DE 19702
(302) 738-5664
C)
The battery for the electric start is located at the front of the craft just inside
the access panels. Wiring diagrams are provided at the end of this manual.
D)
All bolts used on the hovercraft are 5/16" in diameter. The length varies with
location, however all are equipped with two washers, a single lock washer and one
nut. Should one be lost or broken any hardware store will carry replacements.
E)
Frequently check all protective screens to ensure they are properly secured. If
any area is unsecured re-staple the screen in place. If it becomes necessary to replace
a screen the grid spacing is ¼" x ¼".
F)
If the body of the hovercraft is damaged in anyway it can be repaired with
joint compound or Bondo. Simply fill the damaged area, and once dry sand smooth.
Clean the area prior to painting with a semi-gloss black paint.
G)
Should the skirt become torn or damaged it can be repaired with an inner tube
patch kit in most cases. If the tear is large, take extra skirt material and sew and glue
a patch in place. This may require the removal of a portion of the skirt. Remove the
screws that hold the skirt in place to do this. After the repair is made replace the
32
screws and skirt as close to the original position as possible, this will ensure the skirt
remains efficient. Extra skirt material can be obtained from:
Universal Hovercraft
Box 281
Cordova, IL 61242
Phone: (309) 654 – 2588
H)
Periodically check the location of the lift and thrust fans. For the lift make
sure the ductwork is in place and no parts have worked loose. Check the attachment
of the fan hub to the shaft, make sure that no parts are rubbing or in danger of binding.
For the thrust fan, check to make sure the fan is not hitting the protective screens.
33
APPENDIX F: ENGINEERING DRAWINGS
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39
40
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