Team 14: Expedition Camper
Jordan Veltema (ME)
Mitch Hopkins (ME)
Nathan Hiemstra (ME)
Jordan Mast (ME)
Project Proposal and Feasibility Study
ENGINEERING 339 SENIOR DESIGN
2
Executive Summary
This report details the research and design of an expedition camper. The team designed this camper to be
taken off-road over very rugged terrain. The most unique aspect of this project is that the camper is designed
to also function as a boat. The camper’s complex design and robust construction allows it to be pulled over
large obstacles encountered on off-road trails, as well as to be removed from the trailer and placed into a
pond or lake so that it can traverse across water. Team Expedition Camper, otherwise known as Team 14,
has chosen this project for their senior capstone project. After completing the feasibility study, it has been
determined that the creation of this camper is indeed feasible.
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3
Contents
Executive Summary ...................................................................................................................................... 2
Table of Tables ............................................................................................................................................. 6
Table of Figures ............................................................................................................................................ 7
1
Introduction ........................................................................................................................................... 8
1.1
The Project .................................................................................................................................... 8
1.2
Design Norms ............................................................................................................................... 8
1.2.1
Transparency ......................................................................................................................... 8
1.2.2
Integrity: ................................................................................................................................ 8
1.2.3
Trust: ..................................................................................................................................... 8
1.3
The Team ...................................................................................................................................... 8
1.3.1
1.4
2
The Class....................................................................................................................................... 9
Project Management ........................................................................................................................... 10
2.1
Project Breakdown ...................................................................................................................... 10
2.1.1
Frame Assembly ................................................................................................................. 10
2.1.2
Boat and Camper Design .................................................................................................... 10
2.1.3
Suspension .......................................................................................................................... 10
2.1.4
Hitch Design ....................................................................................................................... 10
2.1.5
Launch Mechanism ............................................................................................................. 10
2.2
Schedule ...................................................................................................................................... 11
2.2.1
Task List.............................................................................................................................. 11
2.2.2
Gantt chart ........................................................................................................................... 11
2.3
3
Team Roles ........................................................................................................................... 9
Budget ......................................................................................................................................... 12
Method of Approach ........................................................................................................................... 13
3.1
Research ...................................................................................................................................... 13
3.1.1
Hitch Research .................................................................................................................... 13
3.1.2
Trailer Research .................................................................................................................. 13
3.1.3
Boat Research ..................................................................................................................... 13
3.1.3
Camper Research ................................................................................................................ 13
3.1.4
Motor Research ................................................................................................................... 13
4 Requirements ......................................................................................................................................... 14
4.1
Safety .......................................................................................................................................... 14
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4.2
Operating Conditions .................................................................................................................. 14
4.3
Functionality ............................................................................................................................... 14
4.4
Regulations ................................................................................................................................. 14
5 Project Specifications............................................................................................................................. 15
5.1
5.1.1
Size ...................................................................................................................................... 15
5.1.2
Weight ................................................................................................................................. 15
5.1.3
Durability ............................................................................................................................ 16
5.1.4
Aesthetics ............................................................................................................................ 17
5.1.5
Usability .............................................................................................................................. 17
5.2
6.
Camper ........................................................................................................................................ 15
Boat ............................................................................................................................................. 17
5.2.1
Materials ............................................................................................................................. 17
5.2.2
Shape ................................................................................................................................... 19
5.2.3
Stability ............................................................................................................................... 19
5.2.4
Launch Parameters .............................................................................................................. 24
Design Process .................................................................................................................................... 26
6.1
Tub Design................................................................................................................................... 26
6.2
Boat Hull...................................................................................................................................... 27
6.3
Top .............................................................................................................................................. 28
6.4
Windshield and Hatch ................................................................................................................. 30
6.5
Trailer .......................................................................................................................................... 30
6.5.1
Suspension Analysis ............................................................................................................ 30
6.5.2
Trailer Jacks ......................................................................................................................... 32
6.6
Strap Sizing .................................................................................................................................. 32
6.7
Manufacturing ............................................................................................................................ 33
6.8
Design Calculations ..................................................................................................................... 33
6.8.1
Hitch .................................................................................................................................... 33
6.8.2
FEA Models ......................................................................................................................... 36
6.8.3
Motor .................................................................................................................................. 39
7. Testing................................................................................................................................................... 40
7.1
Safety .......................................................................................................................................... 40
7.2
Launch Capabilities .................................................................................................................... 40
7.3
Strength ....................................................................................................................................... 40
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8 User Friendly ......................................................................................................................................... 41
8.1
Detachability ............................................................................................................................... 41
8.2
Mobility....................................................................................................................................... 41
9 Business Plan ......................................................................................................................................... 41
9.1
Market Competition .................................................................................................................... 41
9.2
Break-even Analysis ................................................................................................................... 42
10 Conclusion ........................................................................................................................................... 43
11
Acknowledgements ......................................................................................................................... 43
12
Bibliography ................................................................................................................................... 44
Apendix A: EES Calculations .................................................................................................................... 45
Appendix B: Design Drawings .................................................................................................................. 47
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Table of Tables
Table 1: Anticipated tasks for design and build of the Expedition Camper. .............................................. 11
Table 2: Cost Estimate ................................................................................................................................ 12
Table 3: Market Research of Expedition Camper ....................................................................................... 16
Table 4: Two capacities of typical off-road vehicles .................................................................................. 16
Table 5: Properties of common hull materials ........................................................................................... 18
Table 6: Component Weights ..................................................................................................................... 20
Table 7: Weight Calculations ...................................................................................................................... 23
Table 8: Off-road campers and their base purchase prices. ........................................................................ 42
Table 9: Cost per camper and annual fixed costs. ....................................................................................... 42
Table 10: Break Even Analysis for Expedition Camper ............................................................................. 43
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Table of Figures
Figure 1: The Gantt chart above gives a visual for the anticipated schedule for our team. ........................ 12
Figure 2: Angle of list as a function of the width of the boat. .................................................................... 21
Figure 3: Distance boat lists into the water as a function of width of the boat. .......................................... 22
Figure 4: Distance Camper will sink into water based on weight ............................................................... 24
Figure 5: Camper height dimensions for launch parameter reference. ...................................................... 25
Figure 6: Dimensions and calculations to find height difference between points A and B ........................ 26
Figure 7: Approximate dimensions for Jeep-styled tub portion of camper................................................. 27
Figure 8: Approximate boat hull dimensions. ............................................................................................. 28
Figure 9: Approximate top dimensions. ...................................................................................................... 29
Figure 10: Approximate roll bar dimensions. ............................................................................................. 29
Figure 11: Leaf spring suspension system .................................................................................................. 31
Figure 12: Air bag suspension system ........................................................................................................ 31
Figure 13: Stacker jacks and scissors jacks ................................................................................................ 32
Figure 14: 501 with a 510 off-road trailer hitch by Lock N’ Roll .............................................................. 34
Figure 15: Solid works model of three axis hitch ....................................................................................... 35
Figure 16: Trailer Strength FEA ................................................................................................................. 37
Figure 17: Trailer Displacement Figure ...................................................................................................... 37
Figure 18: Boat Stress FEA ........................................................................................................................ 38
Figure 19: Boat Deflection FEA ................................................................................................................. 39
Figure 20: Preliminary design drawing. ...................................................................................................... 47
Figure 21: Side view, top down. ................................................................................................................. 48
Figure 22: Side view, top up ....................................................................................................................... 48
Figure 23: Front View ................................................................................................................................. 49
Figure 24: Top View ................................................................................................................................... 49
Figure 25: Boat removed from trailer. ........................................................................................................ 50
Figure 26: Colored side view, top down. .................................................................................................... 51
Figure 27: Colored side view, top up. ......................................................................................................... 51
Figure 28: Colored perspective view showing entrance. ............................................................................ 52
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1
Introduction
1.1
The Project
Team 14, Expedition Camper, is designing and building a multipurpose recreational unit. The design allows
the trailer to have a detachable section which can be loaded into the water and driven away as a boat. The
product is aimed at outdoor, wilderness enthusiasts who enjoy the beaten trail rather than the paved road.
The unit is lightweight and durable allowing it to travel on rugged terrain. The unit is sleek, aesthetically
pleasing, as well as aerodynamic. The watercraft portion is easily detachable from the trailer and has the
ability to move through water. Optimization calculations are used to determine the best combination of all
engineering aspects.
1.2
Design Norms
As Calvin engineers in training, our team strives to uphold Christian values in the design of the unit. In
order to uphold these Christian values, the following design norms are being implemented.
1.2.1 Transparency
In order for the Expedition Camper to appeal to the greatest number of people, it is designed so that the
customer can learn to use it rather easily. The team is ensuring that the design of the Expedition Camper is
not only user friendly, but also that it holds in high regard the safety and well-being of the end user.
1.2.2 Integrity:
In order for the Expedition Camper to fulfill the design norm of integrity, it is designed to be intuitive and
easy to operate. The design is simple enough for the common user to understand how it works.
1.2.3 Trust:
The Expedition Camper itself is a good concept, but in order to meet the design norm of trust, it also has to
endure sustained use. The Expedition Camper is strong and reliable. The user will feel completely safe
when using the product.
1.3
The Team
The team consists of Nathan Hiemstra, Mitchell Hopkins, Jordan Mast, and Jordan Veltema. Each member
is studying in the mechanical concentration of engineering at Calvin College. Jordan Veltema has some
background in manufacturing, as well as experience with automotive body repair. Both Jordan Mast and
Nathan Hiemstra have worked at Innotec for the past two years and have gained experience with
manufacturing equipment. Mitchell Hopkins has grown strong in the use of design software as he has been
working with Progressive Surfaces for the past two years.
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1.3.1 Team Roles
Nathan Hiemstra – Design and Manufacturing
Nathan has a large amount of knowledge with regard to manufacturing, as well as skills in sheet metal
work, welding, and fabrication of various metal products. He is in charge of managing the construction of
the prototype and is working closely with Mitchell to develop a proper prototype design that allows for ease
of manufacturing. This also includes allocating people and resources to fabricate all of the necessary parts,
welding, and subassemblies to build the prototype.
Jordan Mast – Website Design/ Team Management
Jordan has the most knowledge with respect to website design and team management, as well as a strong
knowledge of metal fabrication. He is in charge of creating and keeping the website up to date, as well as
being heavily involved with the manufacturing of the prototype. Furthermore, Jordan is tasked with
managing the team ensuring that they stay on schedule and within budget.
Jordan Veltema – Documentation
Jordan has excellent editing and documentation skills, as well as an expansive knowledge about cars and
other vehicles. He is in charge of making the final edits on all written documents done collectively by the
team, and he also is assisting in the design and building of the prototype.
Mitchell Hopkins – Design and Analysis
Mitchell has a vast knowledge of computer software design. His extensive experience with the Solidworks
software package allows him to construct a detailed 3D model of the prototype. He is in charge of creating
a complete model of the project as well as performing Finite Element Analysis of various parts or
subassemblies. He is primarily working with Nathan and Jordan Mast in order to ensure that manufacturing
of all of the non-purchased parts goes smoothly.
1.4
The Class
This project will span the entire two semesters of the team’s senior year in Calvin College’s engineering
program. The senior capstone project class challenges the students in the program to use all the knowledge
they have gained to tackle a real-world project. With the knowledge and experience our team has gained
over the past few years, the team is creating something unique and fun. Using gained knowledge, the team
is performing detailed studies and calculations to determine the best way to design and build our product.
By the end of the class, the team will have a product that will be presented on senior design night. The
team’s ability to solve complex problems will be represented by our end product.
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2 Project Management
2.1
Project Breakdown
The project is broken down into five main categories, each of which have a significant role in the final
outcome of the design. The five sub-sections of the project include frame assembly, boat and camper design,
suspension, hitch design, and launch mechanisms. Each member of the team has assumed responsibility of
certain tasks, but as a whole the team is working together to make sure each is done well.
2.1.1 Frame Assembly
The frame assembly is the structural backbone of the entire unit. In order to ensure that the design is strong,
the frame needs to be built carefully. Without a rugged frame the integrity of the entire unit may be
compromised.
2.1.2 Boat and Camper Design
The boat and camper is one combined piece so that it is structurally sound. This is key for when it is being
pulled on rough terrain. It needs to be rugged in order to prevent damage or failure from constant abuse on
unpaved trails. It also is aerodynamic and aesthetically pleasing.
2.1.3 Suspension
Rugged terrain means rugged conditions. The team is analyzing different suspension systems to be used on
the trailer to reduce the impact forces on the unit itself. For structural stability, adding suspension is a big
help. In the final design the team is using either a typical leaf spring suspension system or an airbag
suspension system.
2.1.4 Hitch Design
Typical hitches do not allow for multiple axes of movement. Taking a trailer off-road brings with it the
obstacles of uneven pathways. A typical hitch only moves from side to side. For this project the team wants
a hitch that can move on multiple axes. The hitch must be able to move multi-axially. This will allow the
trailer to move more freely from the vehicle as it is being pulled over different obstacles.
2.1.5 Launch Mechanism
Having a unit that can be taken to remote areas makes conventional methods of transferring a boat between
a trailer and water hard to do. With this in mind typical boat launches will not be available for use. The
trailer needs to be specially designed for use in a non-typical boat launch scenario. The team is considering
a launch mechanism that will make transferring the boat to and from the water easier in situations where a
normal boat launch is not accessible.
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2.2 Schedule
2.2.1 Task List
The following table shows the task list for the year of what needs to be completed for our project. In order
to finish the project, every item on the task chart will be addressed in some way or manor. Many of these
tasks are addressed in more detail in later sections of the report.
Table 1: Anticipated tasks for design and build of the Expedition Camper.
TASK NAME
DESCRIPTION
PROJECT MANAGEMENT
Determine our goals and estimate time for each task.
GANTT CHART
Plan for the year which will roughly be followed
RESEARCH
Research necessary for all aspects of our design.
BUDGETING
Budgeting to determine the rough cost of our project.
BUDGET PROPOSAL
Finalize total budget.
CONCEPTUAL DRAWINGS
Preliminary drawings of end product
DESIGN
Designing each component to meet engineering requirements.
FEA ANALYSIS
Perform computer simulations to test component strengths
CAMPER
Must be able to handle constant abuse from rugged terrain.
BOAT
Must be safe on water having maximum buoyancy and stability.
PPFS REPORT
Mid-Year report stating the feasibility of the project
MANUFACTURING
Final stages consist of the construction of our project.
TESTING
Final testing will be done on the product
FINAL REPORT
A final report will be issued on the website
2.2.2 Gantt chart
At the beginning of the year the team put together a list of anticipated tasks that would need to be completed.
The task list is shown previously and a Gantt chart is shown below indicating an approximation of how
each task fits within the schedule of the year.
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Figure 1: The Gantt chart above gives a visual for the anticipated schedule for our team.
2.3
Budget
The following spreadsheet provides an estimation of project expenses required for building a prototype
Expedition Camper (Table 2).
Table 2: Cost Estimate
STARTING BALANCE
$ 2,255.00
COMPONENTS
Cost
Remaining Balance
TRAILER & BOAT
$ 800.00
$ 1,455.00
TROLLING MOTOR
$ 250.00
$ 1,205.00
WOOD
$ 100.00
$ 1,105.00
ALUMINUM
$ 425.00
$ 680.00
STEEL
$ 200.00
$ 480.00
ELECTRICAL
$ 75.00
$ 405.00
AIR BAG SUSPENSION
$ 100.00
$ 305.00
MISC
$ 100.00
$ 205.00
CONTINGENCY
10%
RAW MATERIALS
ADDITIONAL
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3 Method of Approach
3.1
Research
3.1.1 Hitch Research
As a team, one of our first steps was to research hitch designs for our project. The goals of our project
require the design to be able to navigate over rough terrain. Typical trailer hitch designs only have one axis
of movement. Our design requires a hitch that can move in three directions, so we needed to find a way to
allow that to happen. To do this we found a design that incorporates three axes of rotation.
3.1.2 Trailer Research
The trailer did not require extensive research. A rugged camper design means that the piece carrying the
camper must be robust as well. Looking into the trailer, we determined that typical trailers, with some
modification, would be more than capable of handling rough terrain. The major strength issues come with
respect to the boat and camper, rather than the trailer.
3.1.3 Boat Research
In order to ensure that the camper can function effectively as a boat on water, research was done on the
shape, weight, and size of the boat. Initial calculations, which are also addressed later, were made to
determine how to design the boat. The team decided that a flat bottom boat, made of aluminum, would be
ideal, but finding a boat with our specific requirements may be difficult.
3.1.3 Camper Research
The camper portion of the project did not require much research. As a group, we know that the frame of the
camper must be strong and durable. Most campers are designed based on the fact that they are pulled on
paved roads, while ours will mostly be pulled off-road. This meant that the team only needed to determine
which materials would be adequate for the design.
3.1.4 Motor Research
Because the unit is able to float on water and in order to make sure the unit does not drift away with the
current; it needs a source of thrust to move through the water. In order to determine the motor that would
be required, research was done to determine what types of motors would fit the specifications of our unit.
Based on weight, size, and water displaced, a motor was chosen.
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4 Requirements
4.1
Safety
The Expedition Camper is designed for one or two people. When it is being used on land as a camper, it is
properly attached to the trailer to ensure safety of the user while moving in and out of the camper. The
transfer of the Expedition Camper on and off of the trailer is simple enough for one person to do it on their
own. The procedure is straightforward and there are no steps involved that would put the operator at risk of
injury.
The Expedition Camper also is able to operate safely as a watercraft. The motor is properly mounted to the
back of the camper, like a typical out-board motor. Proper installations have been made to allow the user
to operate the motor free from any possible safety risks. When the camper is out on the water, it is stable
enough for a person to move about the camper without struggling to stay balanced.
4.2
Operating Conditions
The camper is able to be towed across all types of terrain that a Jeep or truck can travel across. The
Expedition Camper is also able to withstand weathering and impact from rocks and other rough terrain. The
operator can maneuver the Expedition Camper across the water with ease. Operating the throttle and
steering of the motor is comfortable and straightforward. The Expedition Camper also requires minimal
maintenance.
4.3
Functionality
As a multipurpose unit, the Expedition Camper functions as a camper on land and a boat in the water. The
exterior of the camper has an elegant look to it with the interior of the camper having approximately 12 ft3
of storage space for typical camping supplies. The camper also provides proper sleeping accommodations
for various types of weather. One feature of the camper is that it is able to be used on the water for
recreational activities such as fishing and duck hunting. Adding and removing the sides of the camper is
simple enough to do while out on the water. The camper is able to take on small waves while maintaining
stability.
4.4
Regulations
In order for the project to be a legal boat, there are certain equipment requirements given by the United
States Coast Guard that specify what the boat requires. In the state of Michigan there are four equipment
items that are required; personal flotation devices, a bell or whistle, visual distress signals, and a fire
extinguisher. All four of these items are incorporated into the design of the boat so that it is considered a
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legal vessel in the state of Michigan. In order for the project to also be a legal camper, it must have working
tail lights.
5 Project Specifications
In designing an Expedition Camper, there are numerous factors that must be taken into account. Because
the Expedition Camper has the ability to function as both a camper and a boat, discussion of the
multifunctional aspects of the Expedition Camper was divided into two sections: those associated with the
camper portion and those associated with the boat portion. Due to the fact that they are one piece in the
actual design, these discussions somewhat intertwine and overlap.
5.1
Camper
For the camper portion of the design, defined to be the bottom tub and the top, important design factors
include size, weight, durability, aesthetics, and usability.
5.1.1 Size
The first factor researched was size. There are many different dimensions that are important in the design
of an Expedition Camper. The first group of dimensions that were determined describe the usable space
inside the camper. In order to determine acceptable interior camper dimensions, research was performed
with regard to different off-road campers currently on the market. Table 3 summarizes these interior
dimensions for three of the major off-road campers. From these benchmark examples, it was determined
that the interior of the camper should have a width of approximately 5 ft, a length of approximately 8 ft,
and a height of approximately 4 ft. Given these rough dimensions, several other factors were used to
determine more exact interior dimensions.
5.1.2 Weight
Another important factor evaluated was the dry weight of the camper. The dry weight is defined to be the
weight of the camper without the weight that would be added from additional items such as water jugs,
gasoline cans, furnishings, baggage, tools, equipment, and so on. Research of the dry weights of other offroad campers currently on the market was again used in the determination of an acceptable dry weight for
the Expedition Camper being designed. These dry weights are included in Table 3 for the same three offroad campers used for dimension criteria. From these weights it was concluded that the camper should
have a dry weight of 1500 lb., which is on the higher end of the examples provided. This is because it is
assumed that the additional boat functionality, not present in the benchmark examples, adds some extra
weight to the camper.
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Table 3: Market Research of Expedition Camper
TRAILER
LENGTH
WIDTH
HEIGHT
DRY WEIGHT
[IN]
[IN]
[IN]
[LB]
80
54 or 60
45
1500
109.5
53
44.5
1250
107
54
45
1283
MOBY1 XTR1
SO-CAL TEARDROPS
THE KRAWLER
2
ADVENTURE TRAILERS
TEARDROP3
Furthermore, the dry weight and overall weight of the camper become important aspects when evaluated
according to the measure of the tow capacity of the typical off-road vehicle. Table 4 contains research with
regard to the tow capacity of several typical off-road vehicles. This research confirms the maximum dry
weight decision of 1500 lbs and also sets a requirement that the weight of the camper not exceed 2000 lbs
when fully loaded with all accessories.
Table 4: Two capacities of typical off-road vehicles
VEHICLE
TOW CAPACITY [LBS]
JEEP WRANGLER (2 DOOR, 4 DOOR)4
TOYOTA FJ CRUISER
NISSAN FRONTIER
6
5
2000, 3500
4700
6500
5.1.3 Durability
A third factor that was important to the design of the camper is durability. The camper and top are able to
withstand impact forces and heavy vibrations that it encounters given that the camper’s intended use is the
harshest of off-road environments. In order to achieve a design featuring a high level of durability, material
properties in addition to overall structural design are extremely important. Given that the boat portion of
the Expedition Camper is in the most susceptible position to be affected by the harsh environments
1
http://moby1trailers.com/moby1-xtr/
http://www.socalteardrops.com/page.php?p=22
3
http://www.adventuretrailers.com/teardrop.html
4
http://www.jeep.com/en/2013/wrangler/capability/towing/
5 http://www.toyota.com/fjcruiser/features.html#!/exterior/4702/4703/4704
6 http://www.nissanusa.com/trucks/frontier
2
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experienced in an off-road setting, material considerations are discussed in the following boat section of
the report.
5.1.4 Aesthetics
The overall look and feel of the camper also play an influential role in the design. In order for the Expedition
Camper to be a competitive option for outdoor enthusiasts, the design must be aesthetically pleasing. One
of the largest groups of people for whom the Expedition Camper would appeal, would be Jeep owners due
to the Jeep’s extreme level of popularity in the off-road realm. Because of this fact, it was decided that the
Expedition Camper would do well to incorporate Jeep styling. Furthermore, with regard to marketability,
there is no Jeep-styled multipurpose off-road camper currently on the market. The absence of similar
products on the market provide a good opportunity for the Expedition Camper.
5.1.5 Usability
Another critical factor of the project, specifically with respect to the camper portion, is the ease of use. This
is especially true in its application with regard to the top of the camper. This is a crucial requirement
especially when the Expedition Camper is used in its boat function. The sides and roof of the top are easily
removable so they will not obscure the view of users when used in its boat function. To achieve this
transformable functionality, the sides and top of the camper are constructed from a vinyl/cloth material so
that they can be easily zipped out, rolled up, or folded down. This also allows users to stand up inside when
the Expedition Camper is being used as a boat.
5.2
Boat
Designing a camper with additional functionality as a boat presents several other design factors that must
be taken into account. These factors include materials, shape, and stability.
5.2.1 Materials
Correct material selection is pivotally important due to the fact that the Expedition Camper is subjected to
some of the harshest environmental conditions when put to use. Research revealed four potential candidates
for material selection: wood, fiberglass, aluminum, and steel.
In order for the end product to comply with the other design requirements, wood can quickly be eliminated.
This is because the boat portion of the camper must be capable of withstanding harsh conditions of the offroad environment, such as impact loads, abrasive contact, and constant vibrations. Not only would a
wooden hull be impractical for withstanding impacts and abrasion, it also would be susceptible to rattle
apart and therefore would most certainly develop leaks over time. Furthermore, development of a wood
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hull that can withstand the conditions seen in an off-road environment would undoubtedly lead to a design
that does not fit within the weight constraints of the project.
An evaluation of the three remaining materials, fiberglass, aluminum, and steel, reveals that aluminum is
the optimal construction material for the hull of the camper. That an aluminum hull best fits the
requirements of the project is shown from several different aspects. These include strength, weight,
abrasive resistance, and cost.
From a strength point of view, low carbon steel has the highest tensile strength, as shown in Table 5.
However, because a design criterion of the project is that it must be relatively lightweight, building the
camper hull from an extremely dense material, such as steel, most assuredly will lead to an Expedition
Camper that surpasses weight constraints. On the opposite end of the spectrum fiberglass has a relatively
weak tensile strength. While a fiberglass hull could provide enough strength, the amount of fiberglass
needed to build this hull would result in an Expedition Camper that is heavier than desired. The main
interest from a design standpoint is the strength-to-weight ratio of the material. Because 40-45 aluminum
stands between fiberglass and steel with both tensile strength and density, it boasts the highest strength-toweight ratio. Therefore, aluminum is the best candidate for construction material from both a strength and
weight point of view.
Table 5: Properties of common hull materials 7
MATERIAL
TENSILE STRENGTH
DENSITY [LB/FT3]
STRENGTH/WEIGHT
[PSI]
RATIO
FIBERGLASS
18000
95-100
180-189
LOW CARBON STEEL
58000-68000
470
123-145
40-45 ALUMINUM
45000
168
230
Not only does aluminum score high in the strength and weight categories, it also has several other favorable
properties with regard to abrasive resistance and weather-ability. Aluminum is extremely robust. Unlike
fiberglass, it does not gouge or scratch easily. These material properties are extremely desirable for the
expedition camper, given that it will undoubtedly see the occasional brush of a tree branch or impact of a
stone. Additionally, aluminum ranks high in the category of weather-ability. Both steel and fiberglass are
highly susceptible to deteriorate over time. Steel corrodes quickly with the elements, while fiberglass
blisters and delaminates. On the other hand, the only concerns with aluminum are that it can develop cracks
7
http://www.trekkeryachts.com/construction.php
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if cyclically loaded and not reinforced properly and that it can develop corrosion when in contact with
dissimilar metals. However, both of these are easily remedied with care. Furthermore, aluminum is fire
resistant, a valuable aspect given that the camper will be used in campfire settings.
It is true that fiberglass boats are less expensive to produce in a long-run production environment. Once
the molds have been built for the boat, an easy, repeatable process can be used to mold multiple boat hulls.
However, the capital investment costs required for good, production quality molds are staggering. With
aluminum, there are no hefty up-front costs like this required.
5.2.2 Shape
Another important factor to the boat portion of the camper is the shape of the hull. While there are a variety
of boat hall shapes that could be used, such as pontoons, v-hull, or tri-hull, it is clear that a flat bottom shape
best suites the functionality of the Expedition Camper. Unlike other boat bottom shapes, the flat-bottom
provides the lowest profile. This is important for ground clearance when traversing over rough, rocky, and
uneven terrains. It is also important from an aesthetics point of view because it is desired that the Expedition
Camper be disguised as more of a camper than as a boat. Furthermore, a flat-bottom shape allows for the
Expedition Camper boat portion to be launched in more shallow waters than any other hull shape would
offer. This is an important aspect, which will be described more in later sections given that the camper will
need to have the ability to launch without access to a ramp made specifically for launching a boat.
5.2.3 Stability
One of the biggest hurdles in the design of the boat portion of the Expedition Camper is stability on water.
Typically, small aluminum boats are known for being quite unstable on water. For example, small
aluminum boat users are often forced to stay close to the centerline of their boats due to the fact that
movement to the outer edge of the boat causes larges angles of list, or tipping into the water. In fact, these
boats can become so unstable on water that movement of large masses, such as humans, to the outer edges
of the boat can cause the boat to capsize or tip over. Therefore, one of the big areas requiring extensive
research and calculation is stability.
As previously discussed, research showed that a flat bottom boat is not only the best option from an offroad ground clearance and ease of launch-ability point of view, but also from an increased stability on water
point of view. However, there are several other factors that play a significant role in determining the
stability of a flat bottom aluminum boat. The most significant factors include the location of the center of
gravity of the boat, as well the width or breadth of the bottom of the boat.
After performing detailed research with regard to other off-road campers currently on the market, it was
determined that the width of the camper should be approximately 5 ft. Therefore, it is assumed that the
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bottom of the boat hull portion of the camper should have a width that is slightly less, between 4ft and 5 ft.
In order to determine the relationship between boat stability and width, engineering relationships used in
naval architecture are required. Detailed study and research of boat stability relationships used in naval
architecture revealed that the models utilized are quite complex. Therefore, although a complex model for
stability is difficult to implement, by extensively simplifying the model, basic stability information can be
derived.
Specifically, what is of interest is the angle and distance that the boat tips, or in naval architecture
terminology, lists to one side once a person on the boat shifts to the outer side of the boat. Therefore, to
further simplify the calculation, the boat was modeled as a transverse 2D plane of the cross-section of the
boat.
Several parameters are required for calculation of boat stability; the angle or distance that the boat lists.
The first parameter is the center of gravity. In order to determine the center of gravity of the boat, the
weights of major boat components need to be taken into account as well as the weight of a person. The
weights that are assumed for each of the major components, as well as for the person, are shown in Table
6. Note that the center of gravity of the boat is the key component affecting the stability of a boat. In
essence, the lower the center of gravity of the boat, the more stable the boat is when floating and when
loads are shifted on the transverse plane within the boat. The second parameter is the center of buoyancy
of the boat that is found using relationships developed in “Ship Stability for Masters and Mates.” Using
naval architecture theory along with these two parameters and basic trigonometry, the angle of list and
distance that the boat tips when a person shifts from the centerline of the boat to the side of the boat can be
calculated.
Table 6: Component Weights
COMPONENT
WEIGHT [LBF]
BOAT SIDES
90
BOAT BOTTOM
250
MOTOR
60
FRONT, WINDSHIELD, HATCH
140
FLOOR
100
HUMAN
200
Assuming no external forces, such as waves or wind, and that the person is located at the centerline of the
boat, the boat sits transversally flat in the water with no list. In this scenario, the centers of gravity and
buoyancy of the boat are vertically aligned. However, when the person shifts to the outside of the boat, the
boat lists or tips in that direction. The boat lists in the direction that the person moves due to the fact that
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the movement of the person causes the center of gravity of the boat to be shifted in that direction. The boat
has a listing moment until the center of buoyancy changes and aligns with the new, shifted center of gravity.
Under this methodology, Figures 2 and 3 were derived showing both the angle of list as a function of boat
bottom width and the distance that the side of the boat sinks into the water as a function of boat bottom
width.
20
18
Angle of List [deg]
16
14
12
10
8
6
4
2
0
30
35
40
45
50
55
60
65
Bottom Width [in]
Figure 2: Angle of list as a function of the width of the boat.
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70
75
22
7
6
Tip Distance [in]
5
4
3
2
1
0
30
35
40
45
50
55
60
65
70
75
Bottom Width [in]
Figure 3: Distance boat lists into the water as a function of width of the boat.
From Figures 2 and 3, it was determined that a boat bottom width of somewhere between 4 ft and 5 ft should
not be an issue from a stability standpoint. Ideally, the boat would be designed with a bottom width closer
to 5 ft because of the added stability shown by Figures 2 and 3. With the boat designed as such, if a person
moved from the centerline of the boat to the outer edge of the boat, an angle of around 6 degrees would be
incurred, resulting in a 3 inch downward shift into the water. It is deemed by the team that this is an
acceptable displacement.
Finally, it is worthwhile noting that the calculations performed are an extensively simplified theoretical
approximation of the actual situation.
In the realm of modern naval architecture, advanced and
sophisticated computer modeling is used to model and evaluate the stability of boats in all planes and axes
of motion under an extremely large number of conditions. While the model used to derive Figures 2 and 3
is very basic, after correlating these calculations with information provided by boat owners with similar
size boats, the calculations appear to provide an acceptable approximation of the actual situation.
Because one of the major constraints for the Expedition Camper is that it must be lightweight, an
approximate analysis was done to determine the overall weight of both the camper and the trailer. The first
part of Table 7 shows the approximate weight of major components on the camper and boat portion of the
Expedition Camper. Note that this is a dry weight, meaning, it does not include accessories such as
furnishings and other equipment and supplies. The second part of Table 7 shows the approximate weight
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of the trailer portion of the Expedition Camper. The importance of this analysis lies in the fact that it shows
that the project is feasible from a weight standpoint. As an estimate, the team saw that the weight of the
camper portion of the Expedition Camper is less than the max design constraint of 1500 lbs. Furthermore,
the total weight of the camper is less than the max tow capacity of 2000 lbs, from Table 4, of the typical
vehicle that would tow the Expedition Camper. Finally, note that these values are very conservative. In
actuality, they will likely be lower.
Table 7: Weight Calculations
Assembly
Component
Material
Weight [lb]
Hull
Aluminum
400
Base
Aluminum
150
Top
Steel/plastic/cloth
50
Steel/cloth
100
Floor
Wood
100
Hatch
Steel/glass
60
Wall/windshield
Steel/glass
80
Outboard motor
N/A
60
Battery
N/A
30
Fuel Tank
N/A
30
Boat/Camper
Rollbar
Sum
1060
Trailer
Trailer frame
Steel
400
Leaf springs
Steel
60
Shocks
Steel
10
Jacks
Steel
30
Steps
Steel
15
Hitch
Steel
10
Wheels/tires
N/A
125
Sum
650
Sum
1710
Total
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5.2.4 Launch Parameters
An important aspect that was considered in the design of the Expedition Camper are factors affecting how
it is launched into the water. Typically, a boat launch or ramp is used to put a boat into the water. The
purpose of the boat launch is that it more quickly increases the depth of the water with respect to distance
from the edge of the body of water. In other words, a boat launch allows a boat to be easily removed from
its trailer. However, the Expedition Camper has capability of functioning on bodies of water, way out in
the wilderness, where no boat launches are present. The Expedition Camper, therefore, is designed to
launch without a boat launch.
One factor that aids the launch process of the Expedition Camper is the flat-bottom profile of the hull. This
profile allows the camper to be launched in relatively shallow bodies of water. Basic buoyancy calculations
reveal that that the camper requires a depth of approximately four inches to float. Figure 4 shows the
relationship between the distances that the camper sinks into the water and the weight of the camper. Note
that this calculation assumes a bottom area of the camper of approximately five feet wide by 10 feet long.
The Expedition Camper sits relatively high off the ground for traversing rough terrain, but it was also
required that the camper needs to be low to the ground for ease of launching it into the water. A proposed
solution to these height differences is installing an adjustable airbag suspension in place of a leaf-spring
suspension. Not only would this type of suspension provide the adjustability necessary, it would also
provide a smoother ride for traversing rough terrain. Note that these suspension options will be discussed
more in a later section of the paper.
2500
Depth [in]
2000
1500
1000
500
0
0
1
2
3
4
5
Camper Weight [lbs]
Figure 4: Distance Camper will sink into water based on weight
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25
Since the launch sites that will be used are not going to be typical boat launches, certain launch parameters
needed to be met in order to perform a successful launch. Due to the large off-road tires being used, the
Expedition Camper sits high on the trailer, approximately two feet above ground. Assuming a scenario
where the trailer enters the water with the bottom of the lake being flat, the Expedition Camper requires a
minimum water depth of 28” for a successful launch. Below is a schematic of the camper showing the
dimensions of the camper launch requirements. The water level after launch is the water line that the camper
floats at when in the water.
Figure 5: Camper height dimensions for launch parameter reference.
As previously mentioned, the worst case scenario is a flat lake bed, requiring a 28” depth of water at the
tires to launch. This scenario is very unlikely, as most lake bottoms have a grade to some extent. The
distance from the hitch of the trailer to the wheel axle is 10’, and the distance from the wheel axle to the
back of the camper is 4’. Based on these dimensions, a one degree incline of the lake bottom results in the
back of the camper being approximately 2.93” below the hitch height. Furthermore, each additional degree
of incline drops the back of the boat another 2.93”. In regards to the degree of incline, the back of the
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camper drops 0.84”/degree below the camper height in line with the trailer axle. Figure 6 shows the
dimensions used and calculations performed in obtaining these values.
B
A
Y
X
120”
θ
48”
For θ=1 degree:
Y = 120” x sin (1) = 2.09”
X = (120” + 48”) x sin (1) = 2.93”
X – Y = 0.84” therefore for every degree incline, the change in height between locations A and B is 0.84”
Figure 6: Dimensions and calculations to find height difference between points A and B
For example, if the lake bottom has a ten degree incline, the back of the camper is 8.4” below the front in
line with the tires. Due to this, any incline greatly increases the ease of launching the camper. The back of
the camper sits lower compared to the rest, and therefore enters the water first and reduces the upward force
that the camper is experiencing from the trailer bunks.
Design of the expedition camper focuses on compiling the different design decisions that have been made
through both research and engineering analysis. While all components of the design fit together as one
unit, to simplify the design process, the camper will be split into several major components. The major
components of the expedition camper include the boat hull, the tub, the top, and the trailer. Each of these
components is detailed in the following sections.
6.
Design Process
6.1
Tub Design
The tub design of the camper is one of the most crucial components. This is due to the fact that it stands at
the core of the Expedition Camper. Not only does the tub portion form what would be thought of as the
camper portion, the place where the living space is found, it also is the general aesthetic makeup of the unit
making it look more like a camper than a boat. The tub has a width of 59 in and a length of 100 in. Note
also that these tub dimensions are the same as those found on a Jeep Wrangler (years 1997 through 2006),
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thereby fulfilling the criteria that the camper is aesthetically pleasing. Furthermore, a camper tub shaped
and dimensioned after the Jeep Wrangler gives opportunity for other Jeep-based accessories to be applied
to the camper, such as tops. Figure 7 below shows the overall styling as well as approximate dimensions
for the tub portion of the camper.
Figure 7: Approximate dimensions for Jeep-styled tub portion of camper.8
6.2
Boat Hull
As previously determined, a flat bottom shaped hull provides the best options from a variety of different
perspectives, including ground clearance, ease of launch, and increased stability on water. Furthermore, a
flat bottom boat lends itself to easier manufacturing due to the fact that it does not require the formation of
complex shapes. An additional advantage of a flat bottom hull shape is that the shape and form allows for
easier adaptation of a camper, due to the simple rectangular shape of the top rails that a flat bottom boat
hull provides. The boat hull of the camper is designed around the dimensions of the tub portion of the
camper, detailed in the previous section. Figure 8 shows approximate dimensions chosen for the boat hull,
which coincide closely with the dimensions desired for the tub portion of the camper.
http://s213.photobucket.com/user/jscherb/media/Camper/DinootWide1_zpsf2cd9bcf.jpg.html?sort=3&o
=145
8
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Figure 8: Approximate boat hull dimensions.9
6.3
Top
Another key component in the design of the Expedition Camper is the top. The top of the camper must be
easily removable to allow for standing of occupants when the camper is used in its boat configuration.
However, not only does the top need to be easily removable, it also must be lightweight in order to satisfy
the weight constraints of the design. Under these criteria, it was determined that a top made of waterproof
cloth would be the best option, both from a lightweight and a simplicity point of view. Since the team
desires to incorporate Jeep-styling into the design, a Jeep soft top is the logical solution because it satisfies
all design constraints. While some modifications to the top are required to fit the exact application, the
Jeep soft top is the perfect candidate. A 2004-2006 Jeep Wrangler LJ soft-top fits with the current design
dimensions and would only require modification of the side windows. Furthermore, the soft top involves
a framework that allows it to be easily removed by folding down. On a Jeep Wrangler, this framework is
connected to the roll bar. While a new framework and mounting system could be constructed to eliminate
the need for a roll bar in the camper, adding a roll bar to the camper serves as an extra measure of safety,
should the camper tip over when being used on extreme terrains. Therefore, the team decided that a roll
bar would be a good option for the camper. Figures 9 and 10 show approximate soft-top and roll bar
dimensions.
9
http://chicago.craigslist.org/nwi/boa/4225400901.html
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Figure 9: Approximate top dimensions.10
Figure 10: Approximate roll bar dimensions.11
10
11
http://www.netcarshow.com/jeep/2004-wrangler_unlimited/800x600/wallpaper_04.htm
http://www.netcarshow.com/jeep/2004-wrangler_unlimited/800x600/wallpaper_08.htm
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6.4
Windshield and Hatch
A front entrance point is desired on the camper. This is due to the fact that locating the hatch or door for
entering anywhere else on the camper leads to issues of developing a door that can seal when partially
submerged under water. Furthermore, positioning the entrance in the front of the camper allows for the
camper to remain aesthetically pleasing by not hindering the Jeep-styling incorporated into the tub. While
the entrance could be in the rear of the camper, the camper’s motor is mounted in this location. Therefore
this is not a viable option. In addition to a front hatch allowing entrance into the camper, solid walls are
positioned alongside the hatch with windows. This front area acts as a windshield when used in a boat
configuration.
6.5
Trailer
The final major component from a design standpoint is the trailer. While the trailer and its associated
components requires an amount of engineering analysis, the trailer also must fit the camper and boat hull
well. In order to maintain the desired aesthetics, the boat is positioned such that the seam between the
camper tub and the boat hull is in line with the top of the rail of the trailer. This is necessary in order to
ensure the camper look while being pulled on land. Other major design characteristics possessed by the
trailer include fenders, a toolbox, and steps. The fenders are attached to the trailer such that the boat slides
in between them. A toolbox is integrated into the front of the trailer to help conceal the boat hull, as well
as serve as a storage space for the outboard motor when the camper is being used. Finally, steps are
incorporated into the front of the trailer to allow users to easily enter.
6.5.1 Suspension Analysis
Another critical aspect that allows the camper to go off-road is the suspension system of the trailer. Typical
boat trailers have a leaf spring suspension system that absorbs various loadings and vibrations, resulting in
a smoother, less stress intensive ride. For the application of this camper, the team looked at two different
suspension styles; leaf springs and air bags.
As previously mentioned, leaf springs are very typical on most boat trailers and are readily available in
most shops. However, they do not allow for any vertical adjustment of the trailer, which could be an issue
when trying to launch a boat in a location where there is not a standard boat launch. Figure 11 shows what
a typical leaf spring suspension system would look like on a trailer.
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Figure 11: Leaf spring suspension system12
Alternatively, an air bag suspension system does allow for vertical adjustment of the trailer. As seen in
Figure 12, an air bag suspension system attaches to the axle via a few mounting plates and bars.
Figure 12: Air bag suspension system13
The picture shows the axle being cut into two sections for additional flexibility when driving over rugged
terrain. However, the air bags can also be connected to a single axle without being cut. While driving, the
air bags are filled with compressed air to the rated pressure allowing fluid movement while driving. One
unique aspect about the air bags is that they can also be depressed by releasing the air from the bags to
lower the whole trailer by a few inches.
For this project the added adjustability included with the air bag suspension would be very beneficial,
allowing the camper to be launched in remote areas. Unfortunately, budget and time constraints have forced
12
13
http://www.personalwatercraft.com/products/what-to-look-for-in-a-pwc-trailer-1159.html
http://www.naxja.org/forum/showthread.php?t=1002676
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us to use the basic leaf spring design for the suspension system. This is because it does not require any
additional modifications or costs to the type of trailer that we will use.
6.5.2 Trailer Jacks
When the Expedition Camper is being used on land for camping purposes, it will require support for when
a person is inside of it. Four jacks will be included with the camper to place at each corner in order to
stabilize it, similar to typical campers used today. Because off-road tires will be used for the camper trailer,
the camper will be sitting fairly high off the ground. The axle of the trailer will be 16” above the ground,
and the base of the trailer around 8”-10” above the axle, making the required height for the jacks to be a
minimum of 26” extended.
Two different types of jacks were considered for the expedition camper: stacker jacks and scissors jacks.
Images of each are shown below in Figure 1314,15.
Figure 13: Stacker jacks and scissors jacks
Stacker jacks are fairly cheap, but no sizes have been found to be adjustable to more than 17”. Scissor jacks
on the other hand are more expensive, but do have a larger variety of ranges, some of which being able to
extend to more than the 26” required. One consideration was having blocks to be placed under the stacker
jacks, giving them the extra 10” needed. This option was decided against because it would not be as stable
and would take up more storage space. After discussing the available options, it was decided that the best
option is to use 30” scissors jacks, costing around $100 for the pack. These were the best option because,
although they cost more, they provide a safer and more secure foundation for the camper, adhering to the
design norm of trust.
6.6
Strap Sizing
In order to ensure that the boat does not bounce off the trailer, a set of ratchet straps are installed to hold it
in place. These straps have to be strong enough to hold the boat in place while being pulled over rough
terrain. This means that a lot of force will be acting on the straps and proper size must be considered. The
14
15
http://www.etrailer.com/Trailer-Jack/Stromberg-Carlson/JSC-30.html
http://www.etrailer.com/Trailer-Jack/Ultra-Fab-Products/UF48-979003.html
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team determined that if the boat were to bounce excessively a strap would feel the entire weight of the boat,
which was determined to be a maximum of 1500 lbs. By using this information the team decided to use
four straps that are rated for the weight of the boat. This will give us a large safety margin and ensure that
our boat will not bounce off the trailer.
6.7
Manufacturing
After obtaining the proper funds, the team will begin manufacturing by purchasing both an aluminum flat
bottom boat and trailer as well as designing and fabricating an aluminum Jeep tub. The team will then
modify the boat so that it will allow the Jeep tub to be connected to it via a watertight weld. Once this is
completed, the team will fabricate the camper floor and side panels as well as install an easily removable
top. If given time and funding beyond this, the team will design and install interior furnishings and
additional storage compartments.
6.8
Design Calculations
In order to determine if the design would be feasible, basic calculations and conceptual drawings were done.
The size of the trailer and boat determines the overall dimensions of several other pieces in the design. The
team is setting a baseline parameter for the trailer of having the ability to withstand a one-foot drop, such
as might be encountered when running over a rock, and remain structurally intact. We also performed
stability and buoyancy calculations to determine how the camper would perform on water. Under the
assumption of impact forces, FEA analysis was used to evaluate the structural integrity of the design.
6.8.1 Hitch
Since the goal of designing the camper is to make it as rugged as possible, the trailer hitch must match this
goal as well. It was determined that a regular, conventional trailer hitch will not suffice for this project
because of its lack of mobility. A regular trailer hitch has only one degree of freedom that allows it to rotate
around the ball it is connected to. In order for the hitch to be able to fully function as needed in an off-road
situation, it was determined that the hitch needed to have three degrees of freedom. Two options evolved
from this issue; build one or buy one. After doing some research, an appropriate hitch was found that we
could buy. Lock N’ Roll16 designs and manufactures many types of off-road hitches for trailers. Figure 14
shows an example of one of their particular hitches.
16
www.locknroll.com
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Figure 14: 501 with a 510 off-road trailer hitch by Lock N’ Roll17
Unfortunately, the price of this hitch is just over $200 which is too large of an expense given the projects
budget. Further research showed that $150-$300 is a fairly common price range for these style hitches, and
building one is much cheaper than buying one. Due to the large differences in prices, the team decided to
manufacture a hitch to decrease expenses. A search of multiple trailer forums proved effective in finding a
design for the necessary hitch. Using, Solidworks a model for the hitch was then created, and is shown in
Figure 15.
17
https://locknroll.com/gallery/gallery-category/
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Figure 15: Solid works model of three axis hitch
This hitch was designed by Jeff Scherb and has been used with his consent. The team plans to build this
hitch and perform multiple stress tests to confirm its safety. This hitch has the ability to rotate around the
three axes of a standard three-dimensional coordinate system.
6.8.1.1 Hitch Analysis
The hitch is a critical aspect to allow the camper to go off-road, therefore the team determined that an
analysis of the hitch was warranted. Rather than perform an extensive finite element analysis of the entire
hitch assembly, the analysis was simplified down to determining the strength of the pins and bolts in the
hitch. Since the diameters of the pins are smaller than the diameters of the bolts and are made from the
same material, the pins would be the first part to fail. If it is determined that the force to break one of the
pins is much greater than what the anticipated force of the camper on it would be, then it could be deemed
that the whole hitch would be safe to use.
Since the pins would be in shear and not in tension, the shearing force needed to break the pin was calculated
using the tensile strength of steel and the cross sectional area of the pin. As previously stated, the tensile
strength of steel is approximately 58,000 psi. Assuming that the shear strength of a material is roughly
equal to one half of the tensile strength of a material, the shear strength of steel is approximately 29,000
psi. Using this value and a 5/8” diameter pin, the shearing force required to fracture the pin is calculated to
be 8900 lbf. This force is much higher than the anticipated total weight of the combined trailer and camper,
which is less than 2000 lbs, thus making the hitch safe to use.
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6.8.2 FEA Models
Finite element analysis (FEA), using Algor Multiphysics Simulator, is deemed to be a crucial tool in
developing our design. In order to obtain a basic understanding before introducing high levels of
complexity, we are choosing to keep the simulations simple. After a boat and trailer are obtained for the
project, they will be modeled and more detailed FEA analysis will be performed. FEA simulations are used
to determine if the major components of the Expedition Camper will handle stress and deflection under
certain scenarios.
6.8.2.1 Trailer FEA
In order to ensure that everything in our design is safe during travel, FEA analysis was done on the trailer.
The team made sure that the trailer could withstand the impact forces imposed upon the trailer. If the trailer
were to fail the whole unit would be suspect to breaking. Using impact force equations, the team calculated
that if the trailer were to be pulled over a one-foot tall rock and suddenly dropped, the force experienced
by the trailer would be equivalent to about 6000lbs of static load with a safety factor of 2. According to the
FEA model, the maximum force experienced by the trailer is 68000 psi. Note this assumed a worst case
scenario of one wheel absorbing all the impact. The ultimate tensile strength of ANSI 1080 annealed steel
is 89250 psi. Therefore, according to this simulation, the design should not fail. The team also made sure
the displacement would not be excessive and compromise other parts of the unit. The maximum
displacement of the trailer itself does not exceed 1.12 inches according to the model. Both the strength and
displacement diagrams are shown below in Figures 16 and 17.
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Figure 16: Trailer Strength FEA
Figure 17: Trailer Displacement Figure
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6.8.2.2 Boat FEA
Feeding off of our trailer FEA, the team thought about how stresses would travel through the trailer into
the boat itself. FEA models of the boat were done based on the fact that the team would be using bunks to
set the boat on. Figures 18 and 19 show the maximum stress and displacement of our boat under what was
deemed the worst case scenario would be. This scenario puts a large force on the boat and our analysis
shows that, with aluminum material, the design will hold and does not displace too much to compromise
other parts of our design.
Figure 18: Boat Stress FEA
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Figure 19: Boat Deflection FEA
6.8.3 Motor
The motor that the team choose is based on two main factors; the first being the power needed to move our
boat in water, and the second had to do with the storage of the motor when not on water, to promote the
camper look while on land. The way the motor is mounted affects how it can be stored as well as how big
it can be.
6.8.3.1 Power
Determining the power needed for the motor requires some preliminary standards. The power needed
depends on if we want to go fast or if our intentions are more focused on trolling across the water. Based
on the fact that our budget is limited, we decided that a trolling motor is more cost effective. After doing
some research is clear that a basic rule for boating is that 5 pounds of thrust is needed for every 200 pounds
of boat weight. The team has determined that the boat will weigh no more than 1500 pounds. Calculating
the force required with that weight mean the camper will need 37.5 pounds of thrust. Typical trolling motors
of this size cost a few hundred dollars new, but we should be able to find a used one for a fraction of the
cost.
6.8.3.2 Mounting and Storage
One of the more unique problems that the team faced with the design of the product is dealing with the
placement of the motor. On typical boats the motor is placed on the back and simply hangs there when
being pulled around.
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Our concern surfaced with the idea that the unit will sit lower on the trailer than a typical boat. This could
cause the hanging motor to bottom out on the ground where it is being pulled. Along with that is the fact
that the unit needs to look like a camper when it is not in the water. Having a motor hanging off the back
during transport takes away from that aspect. For this reason, the team decided to have the motor placed on
the back for use in the water, while also making it easily removable for storage when not in use. This allows
the Expedition Camper to use the motor as a typical boat would and still ride down the road looking like a
camper.
7. Testing
In order to ensure that the final product meets the standards set forth, multiple tests are going to be
performed on the finished product. Several tests will be done in certain categories. These categories include,
safety, launch capabilities, and strength.
7.1
Safety
Safety is our biggest concern when it comes to the actual operation of our product. In order to ensure that
the final product is safe for users, the team will perform basic tests that aim at possible safety risk areas.
These include the procedures of launching the unit into the water, hooking up the hitch to the vehicle, and
typical use of the motor. During the task each member plans to document any concerns or ergonomic
problems that arise in the process. Along with this, the team plans to simulate a typical outdoor adventure
where each feature might be used.
7.2
Launch Capabilities
The team discussed which launch parameters would be deemed necessary in order to easily and safely
launch the product. These parameters have already been addressed in the report and the user should follow
these guidelines. We plan to launch the product in various conditions under the suggested guidelines. If this
task is too difficult for the team to perform under the specified conditions, then we will have to modify the
launch parameters or the prototype.
7.3
Strength
Overall strength of the camper is the biggest contributor to a successful end product. Without the strength
required, the unit will crumble in harsh terrain. The team plans to take the camper on a typical rugged trail
and test its integrity to make sure that it meets our expectations.
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8 User Friendly
Designing a user-friendly product is one of the biggest things for which the team strives. The team wants
to make sure that when the customer buys our product, they feel as though they do not need to learn any
difficult tasks to operate the camper. In order to achieve this goal, various aspects are considered.
8.1
Detachability
One of the important functions of this project is for the camper to be easily attachable to and detachable
from the trailer. It has been determined that the best way to accomplish this is to use straps as the anchoring
points to the trailer. By installing multiple strap connections to the camper, it is very easy for the operator
to place the camper onto the trailer and safely secure it down. This anchoring method also minimizes the
amount of bouncing the camper experiences when traveling off-road due to the flexibility of the straps.
8.2
Mobility
Another important aspect of this project is the camper’s mobility. Since this is an off-road camper, it is
necessary that the camper is able to navigate over multiple different terrains. It is also necessary that the
camper is able to ride smoothly down the average paved road, but also able to traverse more difficult terrain.
There are two design specifications for the mobility of the camper. The first is that the camper must be able
to be towed over sand or dirt roads in addition to two-tracks that may be cluttered with small stumps and
rocks. The second is that the camper must be able to be launched in a body of water where there is no boat
launch. In order to facilitate these design constraints, the tires and the suspension system have been chosen
to allow for smooth riding down standard paved roads as well as off-road traveling.
9 Business Plan
9.1
Market Competition
There is nothing on today’s market that serves the same purpose as the Expedition Camper. However, there
are currently some campers designed to be hauled to places to which a typical camper cannot go. The unique
aspect of the Expedition Camper is that it serves multiple purposes as a camper and a boat. For the purpose
of studying the marketability of our product, we are considering the Expedition Camper as part of the
market of durable off-road campers. The fact that it can be used as a boat is considered market
differentiation and an expansion to the market of durable off-road campers.
The off-road campers currently on the market range greatly in complexity. The complexity depends all on
how many accommodations are built into the camper. Three major off-road campers and their selling prices
are shown in Table 8.
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Table 8: Off-road campers and their base purchase prices.
TRAILER
BASE PRICE [$]
MOBY 1 XTR18
16,500
SO-CAL TEARDROPS
14,995
THE
KRAWLER19
ADVENTURE TRAILERS
13,852
TEARDROP20
9.2
Break-even Analysis
To estimate the approximate cost of producing the Expedition Camper, research was done regarding the
fixed and variable annual costs that correspond to the various components of the camper. The costs of each
component are shown in Table 2 of Section 2.3. To determine a production cost estimate, all of the costs
that corresponded to each camper were recorded, as well as all of the annual fixed costs such as building
rent, machinery, and insurance. A table of these costs is shown below.
Table 9: Cost per camper and annual fixed costs.
PRODUCTION COST ESTIMATE
COST PER CAMPER
Description
ESTIMATED LABOR
$2,000
40 hr @ 50$/hr
RAW MATERIALS
$2,270
MARKETING
$1,200
DISTRIBUTION
$1,500
ANNUAL FIXED COSTS
Description
UTILITIES
$40,000
WORK AREA RENT
$75,000
10,000 @ $7.5/ft2
INSURANCE
$10,500
10% of building/equip cost
PATENT
$10,000
PROTOTYPE
$30,000
MACHINERY
$100,000
DESIGN
$100,000
Total Cost
$6,970
Total Cost
$365,500
18
http://moby1trailers.com/moby1-xtr/
http://www.socalteardrops.com/page.php?p=22
20
http://www.adventuretrailers.com/teardrop.html
19
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In order to choose a reasonable price to sell the Expedition Camper, break even analysis was performed to
find the minimum required sale price to break even. Below is a summary of the costs and sale price required
to break even based on a production rate of 30 units per year.
Table 10: Break Even Analysis for Expedition Camper
BREAK EVEN ANALYSIS
ANNUAL PRODUCTION
30
ANNUAL FIXED COSTS
$365,500
COST PER VEHICLE
$6,970
TOTAL ANNUAL COST
$574,600
BREAK EVEN SALE PRICE $19,153
10 Conclusion
After the preliminary calculations and finite element analysis (FEA) on simplified models of the design,
the team concurs that the project is feasible. According to the research and engineering analysis performed,
which incorporate safety factors suitable for the design, the team will be able to manufacture the product.
11
Acknowledgements
The team would like to acknowledge the following people for their support and help on the project.
Ned Nielsen – Engineering Professor and team advisor
Jeff Scherb – Aftermarket Jeep parts designer
Phil Jasperse – Metal shop instructor and manufacturing mentor
Jordan Hiemstra – Industrial Designer
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12
Bibliography
Cabela's World's Foremost Outfitter. N.p., n.d. Web. 28 Nov. 2013.
<http://www.cabelas.com/product/Trolling-Motor-Buyers-Guide/532011.uts>.
Derrett, D. R., and Bryan Barrass. Ship Stability for Masters and Mates. Oxford: Butterworth-Heinemann,
2006. Print.
Engineering Toolbox. N.p., n.d. Web. 7 Nov. 2013. <http://www.engineeringtoolbox.com/>.
Riley, William, Leroy Sturges, and Don Morris. Mechanics of Materials. 6th ed. N.p.: Wiley, n.d. Print.
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Apendix A: EES Calculations
"Volume of box"
L_box=8 [ft] * convert(ft, m)
{H_box=(4/12) [ft] * convert(ft, m)}
H=H_box*convert(m, in)
W_box=5 [ft] * convert(ft, m)
Vol_box=L_box*H_box*W_box
"Volume sides"
W_bottom= 52 [in] * convert(in, m)
Vol_sides=(0.5*L_side*H_side*L_box)*2
L_side=(W_box-W_bottom)/2
H_side=H_box
"Volume of curve"
W_curve=W_box
A_curve=2 [ft] * convert(ft, m)
B_curve=H_box
Vol_curve=pi*A_curve*B_curve*W_curve
"Total volume"
Vol_tot=Vol_box+Vol_curve-Vol_sides
Vol_tot_ft=Vol_tot*convert(m^3, ft^3)
"Density of water"
T=298 [K]
P=101.325 [kPa]
rho_water=density(steam, T=T, P=P)
"Weight of fluid displaced"
m_dis=Vol_tot*rho_water
F_dis=m_dis*g
g=9.81 [m/s^2]
F_water=F_dis*convert(N, lbf)
{F_water=1500 [lbf]}
"Tolling Motor"
lb_Thrust_needed = (F_water/200)*5
every 200 lbs weight"
"General Rule of thumb being 5 lbs thrust for
"Shaft Selection"
"Assume 22inch high boat"
H_boat = 22 [in]
Waterline_height = H_boat - H
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"!Stability - angle of list"
"Boat Weights"
W_side=90 [lbf]
W_bottom=250 [lbf]
W_motor=60 [lbf]
W_front=140 [lbf]
W_man=200 [lbf]
W_floor=100 [lbf]
"Heights of mass centers"
y_side=11 [in]
y_bottom=0 [in]
y_motor=22 [in]
y_front=23 [in]
y_man=44.32 [in]
y_floor=4 [in]
"Horizontal distances of mass centers"
x_width=60 [in]
x_side_1=0 [in]
x_side_2=x_width
x_bottom=x_width/2
x_motor=x_width/2
x_front=x_width/2
x_man=x_width/2
x_floor=x_width/2
"Center of gravity"
Sum_weight=W_side*2+W_bottom+W_motor+W_front+W_man+W_floor
x_bar=(W_side*x_side_1+W_side*x_side_2+W_bottom*x_bottom+W_motor*x_motor+W_front*x_front+W
_man*x_man+W_floor*x_floor)/Sum_weight
y_bar=(W_side*y_side*2+W_bottom*y_bottom+W_motor*y_motor+W_front*y_front+W_man*y_man+W_fl
oor*y_floor)/Sum_weight
"Stability parameters"
BM=(L*(B^3))/(12*V)
V=L*B*Draft
L=96 [in]
B=x_width
Draft=4 [in]
KB=(1/2)*Draft
GM=BM-BG
BG=KG-KB
y_bar=KG
"Angle of list"
GG_1=(W_man*d_shift)/Sum_weight
d_shift=x_width/2
tan(theta)=GG_1/GM
"Distance tip"
Tip=tan(theta)*x_width/2
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Appendix B: Design Drawings
Preliminary Design Drawing
Figure 20: Preliminary design drawing.
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Current Design Drawings
Using the design process shown above, the following design drawings were developed.
Figure 21: Side view, top down.
Figure 22: Side view, top up
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Figure 23: Front View
Figure 24: Top View
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Figure 25: Boat removed from trailer.
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Figure 26: Colored side view, top down.
Figure 27: Colored side view, top up.
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Figure 28: Colored perspective view showing entrance.
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