1. Freedom Peddlers
Final Paper
Senior Capstone
6/7/15
Client: Robert Heston
Submitted by:
Nazar Baydyuk
Jesse Hutson
Tariq Al-Refai
Tariq Al-Zuhairi
Sean McCoy
Todd Raynes
Matt Hudgins
2. Introduction:
Problem Statement:
The available portable boats that are on the market today do not meet all of our client’s needs.
Paddle boats are large, heavy and slow. Canoes require specialized vehicles for transport and the
active use of your arms in paddling; preventing active fishing while moving. Lastly, motorized
vehicles are prohibited on some of the lakes in the Spokane area and our client would like to fish
on these lakes. So we needed to make him something that will be able to accommodate his
requirements.
Stakeholders:
The stakeholders for this project are our client Robert Heston, our project group, and finally the
WA Department of Transportation. Robert Heston, our client, is having us build the boat that he
has been wanting to build for almost 20 years, so he has invested a lot of time and effort into
making this dream happen. He has countless drawing, measurements and even models that he
has produced over the years, and wants us to base the design off of those. Our design team has a
lot riding on this project because it is required for us to graduate; but we also have an obligation
to Bob to do a good job so that he will enjoy the boat that he has always wanted. As engineers
we want to be able to put forth our best product in which we are capable of making. Finally, the
WSDOT is another stakeholder because this boat will technically be a personal watercraft that
must meet their specifications and requirements.
3. Problem Needing a Solution:
In order to achieve a quality final product, we first looked at the problem in which we faced. Our
client is a fisherman in the Spokane area, but a lot of the lakes around here are motor restricted.
So the problem in which we needed a solution was that we needed to make a more efficient
vehicle for fishing (compared to a paddle-boat or a canoe) that provided access to motor
restricted lakes. We also needed to design and build this boat per requirements of the DOT for
the Northwestern states and any welding code requirements.
Charge:
Our design team has been tasked to design and manufacture a boat that meets our client’s needs.
Some of these needs are to be broken down into multiple parts in order to be portable. It has to
be safe in the way that it will stay afloat and not tip over. We need to build it to support a large
enough capacity; whether it be people only or people and equipment. Finally, probably the most
important requirement is that it must be human powered.
Major Initial Specifications:
In order to meet the needs of our stockholders we will have some specifications that need to be
met. First, the frame must be light weight, corrosion resistant, and neutrally buoyant. This will
allow the boat to be easily carried when broken into seven parts and float in the water. Currently
we are estimating the total weight to be less than 200 pounds. In addition, the corrosion
resistance will allow for a longer life of the boat. We also need the boat to carry three people or
4. equivalent with gear. In order to meet this need we have an estimated size of 12ft long and 6ft
wide in a triangular A-frame shape. These major specifications provide our group with the
framework we need to meet our stakeholder’s needs.
Scope:
We will design and build a pedal boat to our clients’ needs that meets Department of
Transportation’s regulations. This will ensure that our boat meets the state and federal boating
requirements along with our stockholder’s needs. Also since we are familiar with it we will be
using SolidWorks for the 3d modeling of the boat as well as to perform analysis.
Additional Needs:
In order to meet our clients’ needs the boat must be motor less and allow the operator of the boat
to be hands free the majority of the time; though we will install a rudder for when he does need
steering capabilities. We will accomplish this by using an existing recumbent drivetrain design
currently used by competitors in the Human Powered Boat competitions. In addition, we need
our frame to be lightweight and corrosion resistance; to meet this need and keep our overall
design cost low, we will use 6061 T6 aluminum. This will help ensure that our overall weight of
the boat will be less than 200 pounds making it lightweight and easily portable when broken into
pieces.
5. Frame:
Objectives:
Having designed the frame and all corresponding components in the previous quarter, our team
had a lot work to do in order to meet our project objectives. To summarize, the frame was
designed to be disassembled into 4 primary sections, each of which must be compact enough to
fit into the bed of a truck or onto a ski rack. These sections would be held together with pin
connections that could be easily removed without the need of any tools. Another key objective
was to construct the bench so that it can hold a maximum of 3 passengers. We determined that
this would be located at the centroid of the frame. With this information in mind, the
construction of the frame was ready for implementation.
Frame cuts:
The first task was to plan all the cuts to the aluminum material. Figure Fr 1.1 lists every single
aluminum member that needed to be cut. This list was compiled by Nazar, who was in charge of
the frame section. Once the list was prepared, the cuts for the frame were carried out. This
process was carried out with one person measuring and marking the cut, and then a second
person would double check the mark and confirm it was the proper measurement. Once
confirmed, the cut was made and the next piece of aluminum is prepared for cutting. With the
use of the metal chop saw, all primary aluminum members were cut at the proper lengths and
angles; there were no unexpected problems that could not have been anticipated in this phase.
Figure Fr 1.1 outlines the cutting process and Fr 1.2-4 show varies parts of frame construction.
6. Figure Fr 1.1: Frame Cuts and Dimensions
Figure Fr 1.2: Nazar and Matt making a cut as Todd prepares the next.
7. Figure Fr 1.3: Tariq marking his next cut.
Figure Fr 1.4: Matt sitting between the frame members for scale.
8. Creating the telescopic tubing:
The next phase was to make the telescopic sections; unlike the previous phase, this section was a
bit more tedious. It was expected that because the 2 x 2 x ¼” had an inner area of 1.5 x 1.5”, the
1.5 x 1.5 x 1/8” tubing, that would serve as the telescopic bridge, could fit with ease. This was
not the case at all. In reality, the 1.5 x 1.5 x 1/8” would need to be milled down and the inside
edges of the 2 x 2 x ¼” needed be smoothed out. At first the telescopic pieces were filed down
by hand, but it was quickly discovered that utilizing the milling machine was a better alternative.
A total of 5 pieces were milled down; 2 pieces would be used as the connecting bridge for the
front and rear frame sections, and the remaining 3 would serve as the connection points from the
sponsons to the frame. Figures Fr 1.5-7 show the milling process.
Figure Fr 1.6: Telescoping Tubes.
Figure Fr 1.5: Tariq carefully milling a tube. Figure Fr 1.7: Nazar demonstrates the fit.
9. Welding the frame:
With all the cuts made and the telescopic sections
prepared, it was time to begin welding the frame
together. In making preparations for this
endeavor, it was soon learned that welding with
aluminum would prove to be a most difficult task.
This is because aluminum metal conducts heat
very efficiently which meant the material would warp and deform after being exposed to the
torch heat continuously. Our client, Robert Heston, took it upon himself on behalf of our team to
consult with professional welder for J and M Fabrication, Brian Weber. Brian coordinated with
Nazar and Robert to get a plan figured out. Once this was done, the welding began.
The welding was performed at J and M
Fabrication by our client Robert Heston with
Nazar assisting and Brian supervising the
operation. As advised by Brian, each member
being welded was allowed to air cool to prevent
major permanent deformation after a certain time
under the torch. During this time, another section
would be worked on. Each piece was to be
secured with a clamp to prevent deformation as shown in figures Fr 1.8 and Fr 1.9. Lastly, all of
the welding was to be done with a wire-feed welding torch set at moderate amperage to prevent
melting thru the aluminum. With all of these conditions successfully met, the welding was
performed.
Figure Fr 1.8: Front frame securely clamped.
Figure Fr 1.9: Welding the flange.
10. Figure Fr 1.13: First round of welding done.Figure Fr 1.12: Welding the frame.
Figure Fr 1.11: Checking for square.Figure Fr 1.10: J&M Fabrication workshop.
11. Drilling frame holes:
The final stage in frame construction was
drilling the holes. Some of the holes had to be
drilled using the milling machine and drill press,
while others had to be done by hand. As Brian
Weber explained prior to the welding process,
certain sections of the frame were at higher risk
of permanent deformation; if a hole was drilled in such an area there would be great risk in
members becoming misaligned with the holes.
The sponson mounts and telescopic tubing were drilled using the milling machine. One problem
that arose in this process was having misaligned holes for the telescopic tubing; this was caused
by drilling each piece individually and then sliding them in only to find that they were off center.
To rectify this issue, it was decided to have the smaller telescopic piece secured inside the outer
tube and drilled together; this method was effective and all holes were drilled in this fashion.
There was also the issue of spacing out the holes a certain distance apart, but this was fixed with
the use of the built-in electronic measuring tool provided on every milling station. The final step
was to insert the pushbuttons into the telescopic sections and the frame now met the objective of
being easily broken down into separate pieces.
Drilling holes into the frame was done for the bench assembly, drive train assembly, and rudder.
This was a very risky part when it came to drilling, if the drill was not held straight, the chance
of misalignment was almost certain. With that in mind, each section was clamped down tightly
and the holes drilled with great attention. Thankfully the job was done with great care and in the
end the frame came together very well.
Figure Fr 1.14: Drilling the seat pin holes.
12. Conclusion:
To summarize the frame section, our objectives were to make the frame capable of being
disassembled into 4 primary sections and able to fit into a truck bed or ski rack. After outlining
the entire process, the reader has probably surmised by now that the frame was successfully built
to be disassembled into 4 smaller sections. As for fitting into a truck, figure fr-19 proves that it is
able to fit into the back of our client’s truck bed. It should be noted that although figure fr-19
does not have all completed components inside, the bench section was the largest piece to fit.
Parting thoughts:
In hindsight, there were a couple of things that would have been done differently. First, it would
have been better to choose a metal that is easier to weld than aluminum. Our team was extremely
lucky to know a person who was willing to perform the difficult task of MIG welding aluminum
for free. Had we chosen a less conductive material, the welding could have been performed by
our own team members after practicing in the metal shop.
Second, when welding members together in parallel as done for the front member, use a spacer
of some sort to allow for some leeway. The gap that the drive train slides into was very tight and
therefore did not have enough clearance to allow the drive to slide in. This happened when the
main front assembly piece was sandwiched between the 2 drive train members as shown in
figure fr-8 and welded. The neck of the drive train had to be milled down in order to fit into the
gap. When this was realized, the same mistake was not made for the 2 outer pieces of the main
front assembly.
13. Seat:
To accommodate up to three people seated astride, we decided to go with a bench seat located
approximately 70 inches from the front of the boat. The seat was reclined at a 30 degree angle
(with respect to vertical) to allow for the ideal reclined position for the comfort of the driver and
pedaling performance. The depth of the seat is 18 inches. This dimension allows for a relaxed
seating position, with no worry of slipping off while underway. The base of the seat, which is
directly bolted onto the rear members of the frame, can be seen in figure Se 1.1.
To support the driver and passengers, we used a series of automobile safety belts arranged in a
weave in the vertical and transverse directions (see figure Se 1.2). Automobile safety belts were
selected due to the client’s surplus of such material, as well as the low deflection while under a
load.
The weave was constructed with 2” belts placed vertically on 4” centers across the entire seat’s
width. Similarly, the belts woven for transverse support, were placed on 4” centers. However,
Figure Se 1.1: Lower Seat Component
Note that that the location of the bolts connecting to the frame are located at
the ends of the widest portion of this member, and on the two 90 degree
corners. The upper (back) portion was welded to this lower portion.
14. due to the occupant load being applied low in
the seat, supporting belts were not
implemented in the upper half of the seat back.
All belts were secured on either end with
grommets held in place by 3/8” screws.
As the belts needed to be cut to appropriate
length, the ends were melted slightly with a
lighter in order to prevent fraying to as great an
extent as possible. The belt ends were folded over and the grommet holes punched went through
two layers of belt. This made them inherently stronger and less prone to tearing over time. These
holes were formed with a hammer and appropriately sized punch.
To achieve the optimal belt length, we wrapped a
belt around two aluminum members and applied
the appropriate amount of slack. The amount of
slack was increased until occupant slippage while
seated was minimized (see figure Se 1.3). The
length was recorded for this belt and all
subsequent belts were made from this template.
The cross-hatch pattern used, where one belt passes over one and under the subsequent belt, was
selected in order to prevent the lowest possible deflection and to prevent the occurrence of an
occupant falling through the belt weave by forcing neighboring belts apart.
Figure Se 1.2: Seat Mesh Final Configuration
Figure Se 1.3: Back Slack and Wrap
15. We noticed that with repeated loading and unloading, the belts began to degrade around the
grommets. This indicates a fairly short life for this system, but it was designed to the client’s
specifications. Also unknown is the resistance of safety belt material to water exposure. This was
the original reason for selecting a marine-grade mesh.
16. Sponsons:
Concept and Design:
Figure Sp1.1: Hull Geometry Drag Figure Sp1.2: Sponson Design
Figure Sp1.1 retrieved from http://www.rclandsailing.com/catamaran/design.html
One major medium for efficiency losses to occur is due to the drag between the sponsons and the
water. In order to maximize our efficiency, we must minimize our drag. One key to
accomplishing this goal is to minimize the area of the sponsons that is in contact with the water
while still delivering the necessary displacement for our needs.
Figure Sp1.1 provides a measure of how much contact (wetted) area various shapes have for a
unit displacement. The shapes were analyzed with the pictured cross sections when viewed from
above the water and rectangular cross sections when viewed from the front.
We used an elliptical geometry in order to minimize the wetted surface area of the sponsons in
contact with the water for a given displaced volume. The drag with the water is minimized when
17. this wetted area is minimized, thus making our sponsons as streamlined as possible (see figure
Sp1.2). Canoes utilize flat-bottom designs, as do the hulls analyzed in figure Sp1.1. A flat-
bottom design allows the center of mass of the displaced water to be as low as possible. Thus, for
any given displacement, a flat-bottom sponson configuration will allow for the lowest draft
possible. In light of these factors, we elected to use a sponson design with a primarily flat-bottom
configuration.
We rounded the front of each sponson to maintain the ideal elliptical shape as well as to
minimize the possibility of fracturing in the event of a collision. Our design specified that the
rear of each sponson was left tapered and sharp to ease manufacture as much as possible. Using a
flat-bottom design, similar to that used in canoes, allows the boat to ride higher in the water
(lower draft) for a given displacement than a vee-type hull. Decreasing the boat’s draft allows the
boat to be launched while closer to shore, easing its use. A lower draft also makes it less likely
that the boat will run aground in shallow waters.
As weight is added at some distance from the centroid of a structure, the end on the same side as
the added weight will ride lower in the water in order to attain equilibrium. Due to the location of
the entire structure’s centroid being coincident with that of a uniformly distributed triangle, we
were able to design all three sponsons to be the same size. The final sponson dimensions are 54”
in length, 20” in width, and 14” in depth. This yields a displacement of 45.54 US Gallons for
each sponson. For a maximum weight of 1000 pounds, these sponsons allow for a displacement
safety factor of 1.15. With a more likely maximum load of 750 pounds, this safety factor is 1.53.
We decided to use fiberglass for the hull of the sponsons. It is easier to manufacture a highly
smooth surface (with a low coefficient of friction) than it is to do the same for aluminum. The
expected lower coefficient of friction with fiberglass compared to aluminum will further increase
18. the drag, increasing the overall boat’s efficiency. Fiberglass is also easier to form and seal than
aluminum is. With aluminum, the issues of welding a material that melts at low temperatures and
does not glow red prior to melting, arise. Because none of our group has experience welding
aluminum, especially considering the low thickness required of the sponson siding, we decided
that laying up fiberglass would be a simpler approach.
Because we are designing the loaded weight of our boat to be on the order of 1000 pounds, each
sponson needs to be able to withstand about 333 pounds of force on it. A thin layer of fiberglass
would fail to provide the rigidity required on its own, so we are going to be laying fiberglass
over a solid block of rigid polystyrene foam. The pink 2” boards of polystyrene insulation have a
shear strength of 15 psi which allows a shear stress safety factor of 2.88 when we have
8”x8”x0.125” aluminum plate serving as our sponson bracket (see figure Sp1.3). The maximum
load of 333 pounds on each sponson is distributed over 64 square inches, allowing a stress safety
factor of 2.88.
The polystyrene foam that we are using is easy to source from local hardware stores, and is
highly resistant to moisture. Because we need a thickness of 14” for our sponsons, we are going
to laminate seven layers of 2” board together with spray adhesive. For an inconsequential
amount more money, we can purchase the same foam boards with aluminum foil bonded to each
main face. This would ease the bonding of each layer together with adhesive, as the foam would
no longer tend to absorb the adhesive. The lamination between each layer of foam, as well as the
aluminum foil will undoubtedly increase rigidity without increasing weight significantly.
We are using 7 ½ ounce E-Glass fiberglass cloth. This is the type of fiberglass typically used in
boating applications. With three layers of fiberglass, the cloth will weigh approximately five
pounds per sponson. Typically, the cloth absorbs about its own weight in resin, so our finished
19. fiberglass weight will be about ten pounds per sponson. With a foam density of 1.42 pounds per
cubic foot, our total sponson weight should be about 18.6 pounds each.
Using polystyrene as a rigid support structure within the sponson introduces one primary
challenge. Most resins are styrene-based, and would dissolve polystyrene similarly to acetone if
used to lay fiberglass on its surface. Instead of the less-expensive, styrene-based resins, we will
have to use epoxy resin and hardening agent. This is not a financial issue in light of finding the
foam locally, thus avoiding shipping.
Figure Sp1.3: Sponson Bracket Design
Final Product:
After acquiring construction materials, we required a method in which to cut the foam. We
elected to borrow our mentor’s 4.5” hot-wire cutter (with nichrome wire) to cut the foam with
(see figure Sp1.4). We used this to cut each sponson layer separately, tracing out a single layer of
our sponson and this as a guide to trace all of the subsequent layers to match (see figure Sp1.5).
20. Figure Sp1.4: 4.5” Hot Wire
As there were seven layers for each of the three sponsons, the above production technique had to
be repeated 21 times. Due to the error propagation associated with using one inherently flawed
piece to trace others, we found a very low degree of repeatability. Naturally, if one piece is
traced onto another layer of foam, and that outline is cut, error is introduced in both the process
of cutting and in the process of tracing. Our layers, as a result, did not match up well prior to
sanding to finish (see figure Sp1.6).
Once getting all layers cut with the hot wire, we found pieces that matched as closely as possible
and glued them together into three sponson blanks (each seven layers thick). Due to the width of
the foam being only 48” and our sponson overall length being 54”, we had to cut 6” nose pieces
for each layer. These nosepieces were affixed in place at the end of each layer with caulking
agent prior to the gluing of multiple layers together. In order to avoid weak spots traversing
21. entirely through each sponson, we alternated which end had the separate nosepiece between
layers. This assured that any stress concentration issues at these interfaces was minimized by
having a solid layer of foam directly above and below any given nosepiece.
The effect of having alternating nosepiece locations was that two distinct main layer profiles
needed to be cut; nine of one geometry (with the nosepiece section on one end) and twelve of the
other (with the nosepiece on the opposite end). This compounded the issue of dimensional
consistency from one layer to another. The highly specific arrangement of pieces required, made
it time consuming to get to the point where we were ready to begin gluing the layers together.
We selected 3M High Strength 90 spray adhesive to adhere our layers together. We used
caulking agent to affix the nosepieces in place rather than counting on spray adhesive because
caulking agent allowed the more uneven contact surfaces to still bond adequately. We originally
planned to use the same caulking agent to glue our layers together, but we found the application
process very time consuming, so we used spray adhesive instead.
Figure Sp 1.5: Tracing of Sponson LayersFigure Se 1.6: Uneven Cut Layers
22. While less time consuming, the issue of the spray adhesive partially dissolving the foam, arose.
Despite the fact that contact area between the layers was decreased as a result of the foam being
partially eaten away in certain spots, the bond was extremely strong between almost all layers.
We had to be cautious so that we did not apply too thick of a adhesive coat onto the foam
surface. The end result was that only a few layers required a reapplication of adhesive, and all
bonds were quite strong by the time that we were ready to fiberglass.
After we had assembled the three sponson blanks, we realized just how inconsistent our cuts had
been. Extensive sanding was required in order to achieve a reasonably smooth finish over which
we could fiberglass. We borrowed several electric sanders to aid in our efforts, and found that the
orbital sander that we had was, by far, the most effective at removing material.
While our design originally called for a sharp rear edge for the sponsons, we were instructed by
Dr. Weiser that fiber glassing over sharp edges is extremely difficult and tends to produce
bubbles. As a result, we shaped the rear of each sponson to have a much more rounded edge (see
figure Sp1.7).
Figure Sp1.7: Final Sponson Shape (from the Bottom)
23. As the layer edges did not match up at all well, we sanded them all until a smooth contour was
achieved (see the surface finish progression in figures Sp1.8 and Sp1.9). In order to remove as
little material as possible, as well as to decrease the incidence of any dishing from top-to-bottom,
we began sanding at the lowest apparent spot and sanded outwards from there. Going from this
low spot to the adjacent layers radially allowed a very smooth contour to be achieved. A high
degree of smoothness was necessary in order to avoid excessive bubble propagation.
Figure Sp1.8: Surface Finish Early in Sanding
Figure Sp1.9: Surface Finish After Sanding
24. After this, we still had to shape the front contoured section of each sponson. This contour is
important in keeping the flow of water over the hull as laminar as possible, minimizing drag. We
borrowed a larger (18” nichrome) hot-wire from Frank at EWU to make this cut. We found that
regardless of the power setting, the wire became so hot that it melted foam around it by about 0.5
centimeters. This made precision cuts (as necessitated by the front sponson contour) very
difficult to achieve. We had several slips that needed to be sanded out due to the attempted use of
the large hot-wire to make a cut along the desired contour line. After this realization, we made
course cuts with the hot-wire, leaving adequate clearance around the contour line. We then
sanded the excess material off until the desired shape and surface finish was achieved (see figure
Sp1.7).
We had areas containing voids (resulting from the use of spray adhesive), and some minor
recesses in the overall surface that were filled with spackle and then sanded. The sharp edges
were also sanded off to assure that the fiberglass went on as smoothly as possible.
Dr. Weiser brought up the fact that due to the shear strength of this foam being only 15 psi, any
incidence of waves or unexpected impact loads could cause the bracket plate to dig into the foam
and loosen the fiberglass bond. He recommended that we shape a top layer of 0.5” CDX
plywood for each sponson. This would provide a much more solid backing for the plate, and
prevent loosening of fiberglass over time. We took this advice and shaped one plywood top layer
for each sponson. The surface and edges were sanded until a smooth transition from plywood to
foam was achieved for each sponson (see figure Sp1.10).
25. Figure Sp1.10: Sponson just Before Fiberglass Application
Dr. Weiser took part of an afternoon after we had finished sanding our sponsons, and showed us
the exact process needed to fiberglass them. We elected to use three layers of 7 ½ ounce E-glass
for our fiberglass. This was determined based on the use of three layers on surfboards, with 3
ounce glass. Since we were using glass over twice the weight, we decided that this was a
sufficient amount of rigidity. After discussing our plans with Dr. Weiser, he did not object to our
use of three layers, so we deemed this amount sufficient. Before fiber glassing, we traced out six
side pieces, three tops, and three bottoms, for each sponson.
We used a wet-layup process. The first step, after mixing the epoxy and hardener in appropriate
proportions, was to apply an initial layer of resin on the surface in which we wished to glass.
This provided a viscid layer on which the dry fiberglass cloth could stick to. After placing the
26. dry cloth onto the initial resin layer, we placed additional resin onto the surface until all dry areas
were removed.
Our cloth sections were cut such that the two side pieces would overlap somewhat when laid
onto the sponson surface (see figure Sp1.11). We also cut the top and bottom sections to have at
least an inch of overlap with the sides. This assured additional rigidity on the corners, and
prevented any spots in which no glass was present.
Figure Sp1.11: Cloth Overlap on Corners
The overlap on the front of the sponson can be seen. The overlap for the bottom can also be seen,
in the form of cloth hanging off of the bottom of the sponsons.
The biggest issue that we had with laying up the fiberglass was that the cloth on the corners did
not tend to remain adhered to the sponson surface very well (as can be seen in figure Sp1.11,
where the cloth is hanging off of the edges). No matter how much resin was applied to these
regions, the edges would not stay down. This is a problem, as any voids in these areas produce
bubbles, which compound to produce additional bubbles in later layers. One practice that we
used was to cut slits along the edges for the top and bottom layers. This allowed fewer bubbles to
27. develop. Rather than folding over to produce bubbles, the cloth could be layered over itself in
necessary locations (see figure Sp1.11).
Using a tip from Dr. Weiser, we used taught saran wrap layers on these edges to hold the cloth
down while the resin dried (see figure Sp1.12). The saran wrap allowed any developing bubbles
to be smoothed away by hand, and was easily removed after the resin had cured. This was the
single best tip that we received for this project.
Figure Sp1.12: Saran Wrap Application on Edges
The first layer was the most critical, as any voids in the first layer would carry through the
subsequent two. We elected to allow the first layer of fiberglass to fully cure before putting any
more on. We sanded the surface extensively (see figure Sp1.13) and then applied our subsequent
layers. The order of layer application was as follows:
Bottom-Sides-Bottom-Sides-Top-Top-Sides-Top-Bottom
28. Figure Sp1.13: Sanded Finish Prior to Subsequent Layer Application
Take note of the tape applied to all bolts. This was to protect the threads from exposure to epoxy
to as great an extent as possible. However, it was still necessary to run a die down the threads to
clean them up before the nuts could be screwed on.
After the final fiberglass layers had been applied, sanding to a finish comparable to the above
level was attempted. However, with a much larger amount of cured resin present on the surface,
a finish to that same level was not feasible. In the process of sanding regions with bubbles were
removed. Patches were added for reinforcement in appropriate locations. The final surface of the
sponsons was relatively smooth on all surfaces but the bottom. A certain level of porosity was
apparent in the final layer of fiberglass. However, like the surface finish, slight porosity is more
of a cosmetic issue than a functional one. The porosity certainly did not continue through the
29. first fiberglass layer, so with two low-porosity layers beneath, a small amount of porosity was
not a concern.
One undesirable effect of an imperfect surface finish is that any area that is in contact with the
water will have increases form drag. However, because our design was optimized to minimize
drag in the first place, efficiency was still maintained at an acceptable level even with the
increased form drag due to a rougher than desirable surface. The final, painted, sponsons are
visible in figure Sp1.14.
Figure Sp1.14: Finished Sponsons
What we would do differently:
Due to the incredible difficulty in achieving a consistent finish when each layer was cut up
individually, we would likely glue the seven 48”x96” foam boards together, trace out three
identical contours on the top of the board, and simply cut the contours with a saw. We would
have developed a smoother finish initially, leading to significantly less sanding. We would also
make the sponsons slightly wider and shorter, such that a 48” wide foam sheet would have
accommodated the sponson’s length entirely.
30. Drive System:
Concept and Design:
In order to enable our boat to move quickly through the water, we decided to use a recumbent
pedal system utilizing a twisted chain design (Figure Ds 1.1). We chose this design because it
meets our needs in terms of efficiency and the twisted chain drive system has had great success
at many human powered boat competitions. The driver will be seated on a bench where he will
be in a reclined position and from there he will be able to pedal using his feet. The twisted chain
will be attached to a sprocket located on the pedal crank, and directed down to a smaller idler
sprocket. The smaller idler sprocket is attached to a propeller shaft that will directly drive the
propeller. The chain will run through an aluminum tube which will protect the chain from water
when the bottom half of the drive system is submerged. This shaft will then be welded onto a
mount which will be attached via pins to the frame of the boat. This results in a completely
modular design that is easily removed from the frame. Once mounted, the drive system will
allow the driver to travel forward and in reverse by pedaling backwards.
Figure Ds 1.1: http://www.recumbents.com/wisil/hpb/compact_drive.htm
31. We will be using a standard bike pedal crank set for our twisted drive system. The crank will be
approximately 7 inches in length and we will be using standard foot pedals. Attached to the
crank set will be a #25 ¼ inch pitch 45 tooth sprocket. This will be fixed gear, enabling the
driver to pedal both forward and in reverse.
We will be using an ANSI #25 ¼ pitch chain that will be approximately 6.5 feet long. We were
able to approximate the length of the chain since we know the sprocket diameter ratios and the
distance from the center of the sprockets. The chain will run through a 1.5-inch diameter tube
which will protect it from water while the drive system is submerged. The driver will have
access to the bottom of the tube, allowing for the chain to be easily placed onto the smaller idler
sprocket, which drives the propeller. A rubber seal will be placed at the bottom of the tube,
which will assure that no water enters the tube. This seal will also be easy to remove if the chain
ever needs to be replaced.
The twisted chain drive system will be mounted to a rectangular 4”x6” plate. The mounting plate
will be welded eight inches below the top of the chain tube. The mount for the pedal crank set
will also be welded directly to this plate and the side of the chain tube. This will provide the
support for the crank set and the offset needed for the chain to run perfectly down the center of
the chain tube. There will be four holes towards the corners of the mounting plate where the
universal pins will be inserted to secure the entire drive system to the frame of the boat.
32. Final Product:
There were several stages to building the drive system. First, we purchased all the material
needed to build the drive system. Then modifications needed to be made to some of the
components to meet our design needs. After modifying the components then we was able to
build the drive system.
For the bicycle crank we decided to use a one piece crankset. This was chosen for several
reasons. First, it meet our design needs. Meaning it would allow the driver to pedal forward and
backwards. Secondly it was also more cost effective to go with the one piece crankset versus the
Figure Ds 1.2: Exploded Drive System
33. three piece crankset. In addition using the one piece crankset meant that there was no need to
purchase an internal bottom bracket. This meant that an external bottom bracket contain loose
ball bearings could be used which was significantly cheaper.
Modification was necessary for the ANSI #25 ¼ inch pitch 45 driver sprocket to fit on the one
piece crankset. Using a mill we were able to flatten the sprocket (Figure Ds1.3) and bore the
center hole larger to meet our needs (Figure Ds 1.4). Also a small ¼ inch diameter hole was
drilled into the sprocket for the drive pin on the crankset to fit into. For the driven 10 tooth
sprocket we only had to bore the center diameter out to be slightly larger in order to
accommodate the bolt that connected the driven sprocket to the bottom bicycle bracket.
Fortunately we were able to use spare 2x2 inch aluminum tubing left over from the frame to
make the crankset mount. This required cutting a semicircle with a 2.3 inch diameter on the top
of the tube so that the crankset cylinder housing would sit evenly. This was very important
because if the crankset did not sit perfectly horizontal then there would be an issue with the chain
Figure Ds 1.3: Milling the sprocket. Figure Ds 1.4: Boring a center hole.
34. running smoothly down the chain tube and the driver comfort. Initially the semicircle was cut by
hand using a plasma cutter. However, since this was not as precise as we would have liked it we
decided to use the mill to cut the semicircle to our liking (Figure Ds 1.5).
One of the obstacles that we had to overcome when designing and building the drive system was
how to properly secure the propeller axial to the chain tube. It was important that the propeller
axial did not move as it would cause the chain to slip. So in order to ensure that there was no
movement we decided to machine a housing for the propeller axial to sit into. A bar of 2x1.75
inch 6061 aluminum was used for the housing. Using the mill we were able to drill out three
different diameter holes for the propeller axial to sit firmly into (Figure Ds 1.6). This not only
meet our needs for securing it firmly to the chain tube but also allowed easy removal of the
propeller axial if there was a need to for repairs.
Figure Ds 1.5: Milled semi-circle.
35. For the sake of disassembly and portability of the boat the drive system needed to be mounted to
the frame to where it could be effortlessly taken on and off. In order to do this we needed a
mounting plate that would securely hold the drive so a square 2x2 inch hole was drilled using the
mill into a 6x6 3/8 thick aluminum plate. The thickness of the plate was increased from our
original design for added rigidity and to make it easier to weld both the crankset mount and the
chain tube to it. The 2x2 inch hole would allow the chain tube to fit snuggly inside. Once the
chain tube was welded to the mounting plate then the drive was secured and could be attached to
the frame. Bolts with wings nuts were used to attach the drive securely to the frame.
Figure Ds 1.6: Axle housing.
Figure Ds 1.7: Mounting plate.
36. To put tension and direct the chain down the tube tensioners were necessary. Two steel idler
sprockets were used to guide the chain towards the middle of the tube and provide enough
tension where the chain would not slip off of the driver or driven sprocket. Initially we designed
tensioner arms that would attach to the crankset mount. However, this design was scrapped for a
simplifier and more efficient design. As seen below Figure Ds 1.9 has an arm where we would
have to account for slipping due to a rotational moment. Instead with the tensioner seen in Figure
Ds 1.8 there is no rotational moment about an arm and the tension can be easily adjusted by
sliding them in or out.
Once all the components of the twisted drive system had been made or modified to our needs we
were ready for welding (Figure Ds 1.10). With the assistance of our client Robert Heston we
were able to MIG weld the drive together in about one hour (Figure Ds 1.11). After the welding
was completed we were ready for testing.
Figure Ds 1.8: Tensioning Bracket. Figure Ds 1.9: Tensioning Arm.
38. After the welding was completed we were ready for testing. Our initial dry test showed us that
the chain needed to be slightly adjusted. We removed 3 links from the chain so that the length
was sufficient for the tension require on the chain. We also made adjustments to the crankset by
tightening the clamps holding the driver sprocket in place. Once the preliminary dry test were
done we were ready for water testing. We took the boat to closest local lake to perform these test.
Once assembled and on the water the boat only made it a few feet before the driver sprocket
began to slip. Even after tightening the clamps on the crankset it was not enough to hold the
sprocket in place. This was due to the increase resistance in pedaling now that the drive system
was submerged in the water. After our initial test we modified the driver sprocket by placing a
hole in the for the driver pin on the one piece crankset to fit into. This allowed the driver
sprocket to move in sync with the one piece crankset without slipping. Once this modification
was made we took the boat back out for a second round of testing. This time the drive worked
well. The only complication that we had was when pedaling at high rates the chain would begin
to rise up on the driven sprocket. This was due to the chain tension be so significant that it would
pull the propeller axial up slightly causing. When the propeller axial is not completely horizontal
then the driven sprocket is not completely vertical and slipping of the chain will occur.
What we would do differently:
Since there was movement of the propeller axial when the chain was very tight we would go
back and make adjustments to the propeller axial housing. More precise machining of the
housing would lead to a more secure fit of the axial. This would allow us to adjust the chain
tension to a reasonably high pounds-force without worry about whether or not it would pull the
propeller axial up.
39. Propeller:
There are two methods to consider for our
propeller design. The first method is to use APC
fiberglass model airplane propellers. These are
commonly used in the Human Powered Boat
competitions and come in 14”x14” and 16”x16”
sizes that work well within the projected speed
and power range of human powered boats. The
second method will be to make a jig and form
propellers out of 1.5” x ¼” 304 stainless steel bar
stock. Creating our own propellers will cut down
on overall expenses but will dramatically
increase the amount of time required to build.
That being said, we elected to make our own
propellers first. The durability would be better and
the experience would be beneficial.
The general shape of the propeller foil is referred
to as an E193 and is shown in Figure Pr1.1. This
is the shape of the blade that we produced. The
overall diameter is 16”, making each individual
blade around 7.5”.
We started with a design laid out on engineering
Figure Pr1.1: E193 Airfoil Design
Figure Pr1.2: Design Blanks
Figure Pr1.3: Flat Bar
Figure Pr1.1: E193 Airfoil Design
Paperdesign,CardboardBlank,EtchedSteel
Four blades cut to length and labeled
40. paper and used it to make a cardboard blank. On the blank, we made
sure to label the leading and trailing edges, as well as the grip line
that we used when we twisted the blades. The blank was then placed
on the stainless bar and traced. After tracing, we used a straightedge
and scribe to etch the lines and ensure they are still visible
throughout the process.
Each of the blades were laid out in this manner and then cut to
length with a large chop saw. They were all labeled with a marker to
make sure we kept them in the right orientation during the bending
process. This can be seen in Figure Pr1.3. The grip line was marked
on each blade and then we proceeded to twist them.
We used a benchtop vise to grip about 1/2” of the inside edge of the
blade for twisting. Then we lined up the center mark on a circular
protractor with the edge of the blade. On one edge of a large
adjustable wrench, we attached an indicator arrow that was made out
of cardboard. The indicator allowed us to determine the angle of
twist on the blade. The setup before and after the first twist can be
seen in figures Pr1.4 and Pr1.5. The wrench was centered on the grip
line for this. With the inside edge in the vise, the blade was twisted
33 degrees. It is then flipped over so that the outside edge is in the
vise and twisted another 15 degrees. The direction of twist must line
up for the inside and outside and it also determines the direction the propeller must spin to
provide thrust. Our propeller was twisted counter-clockwise and spins counter-clockwise on the
Figure Pr1.4: Twist Jig
Figure Pr1.5: Twist Jig
After Twisting
Before twisting
41. drive. We did this to ensure that the sprocket on
the inside of the drive was constantly being
tightened. We also elected to twist the blades
prior to cutting out the overall shape because we
didn’t want the twist to happen exclusively in the
weaker area of the blade.
After twisting, we cut the majority of the extra
material off with a hacksaw before taking it to a
stand grinder. We used the grinder to take off the
remaining material and form the general outer
contour of the blades. Figure Pr1.7 shows two
blades prior to being shaped and two blades after
being shaped. We made sure to place the blades
against eachother to ensure that the twist was
relatively the same for each pair of blades.
By far the longest and most involved portion of
blade production came in the contouring of the
airfoil shape. The general ideal is that the leading
edge of the blade to approximately 1/3 of width
of the blade is at one steep angle and the
remaining 2/3 of the blade is at a more shallow angle. The underside is carved out a little like a
channel. To form the top side of the blade, we used long strokes on the stand grinder along the
entire edge to gradually form the angle we wanted. The idea was to take the blade down to a near
Figure Pr1.6: Cut Blade
Figure Pr1.7: Outer Contour Formed
Figure Pr1.8: Twisted Blade
42. knife edge without making it sharp and dangerous to handle. During this process, the steel heats
up significantly. We had a large bucket of cold water handy to help dissipate the heat quickly.
When the top side was close to our desired contour, we used an angle grinder with a sanding disc
to improve the quality of the surface and smooth the blade. The angle grinder with a grinding
disc was used to form the channel on the underside of the blade. The channel was cleaned up
using the same sanding process. When the grinding and sanding was complete, we used a stand
buffer to further clean the surface of scratches to
cut down on drag in the water. Figure Pr1.9
shows the blades in three stages: beginning
contouring, completed contour, and buffed
finish. It is important to note that during the
process of contouring, probably the heating and
cooling changing the internal stresses of the
steel, the blades tended to curve outward. By placing these blades
against one that hadn’t been contoured, we were able to carefully
bend them back into their original shape.
The finished blades were then welded to a collar at an angle of 18
degrees. This gave us an overall final angle of twist at 66 degrees
from the collar. To our surprise, a 15mm deep well socket worked
perfectly as a collar and slide onto the square drive shaft to prevent
the propeller from spinning freely. Depending on the socket, you
may need to remove a nickel coating prior to welding as was the
Figure Pr1.9: Blade Stages
Figure Pr1.10: Finished
43. case for us.
All of the precautions and careful measurements yielded a very balanced propeller. It spun
extremely well with almost no vibration. On our test runs, the propeller and drive produced a
large amount of thrust. The single propeller was able to propel our boat to around 5 knots and the
design is based off of the propeller used in the human powered boat speed record of about 22
knots. It is rather surprising how much for it takes to spin the propeller in the water. Blades any
wider than these would require a significantly lower gear ratio to work effectively.
Knowing what we know now, we probably wouldn’t change much. We would probably use an
angle grinder to do the majority of the contours because of how quickly it takes material off. The
tradeoff is that it is much easier to take too much and ruin the blade. Next, we would probably
experiment with different blade length and width setups. The people that build these for
competitions use anywhere from a 14” to a 20” propeller with widths from 1.5” to 3”. Couple
this with a different gear ratio and you may be able to produce higher thrust more efficiently.
44. Steering System:
Concept and Design:
The rudder is a device that helps to navigate through fluids. Most vessels, such as ships, boats,
submarines, and aircrafts that moves through fluid using it. It is operated by transmitting the
fluid past the vessel. Basically, it is consist of a uniform plane or sheet of material attached with
hinges to the tail (Figure St 1.1). The rudder manufacturers usually shape it to reduce the drag
forces. Moreover, in most watercrafts there is a lever arm called a tiller that is used by the
operator to control and turn the vessel.
Figure St 1.1: Rudder Shapes.
45. Our steering method involves only one hand by the driver. Moreover, it does not require constant
attention while moving in one direction. The rudder is placed in the middle of the boat, like in
most low speed vessel, behind the drive system. This positioning allows the vessel to steer in a
manner similar to a car and it is easy to become accustomed to. Generally, rudders can be either
the unbalanced type, or designed with some degree of balance to make turning easier (Figure St
1.2)
On our design, we chose the balanced rudder because it is the most common type that is used in
small boats. The balanced rudder is divided in to two areas by shifting the connecting rod that
attached to the rudder. The forward portion of the rudder blade help to reduce the amount of the
force needed to turn the rudder. The forward area of such a rudder has to be less than 20% of the
total area in order to get the best performance (Figure St 1.3).
Figure St 1.2: Rudder Styles.
46. Designers often crowd the rudder tightly behind the propeller. A much better practice is to move
it back. When the rudder is moved back, the propeller vortices hit it much less fiercely and flow
is more defined.
The Final Product:
Our steering system of the boat consists of four main parts (rudder, connecting rod, lever, and
two aluminum sheets). The rudder is made of one piece of aluminum sheet that has a thickness of
(1/8 in). Since it is not very thick, we used a shear cutting machine to cut it, and a metal file to
round the edges. After that, the rudder plate is inserted then welded to a slot at the end of the
Figure St 1.3: Rudder Shape and Dimension.
47. aluminum connecting rod. The rod is (60 in) in length and (1 in) diameter. Another slot was
made at the far end of the connecting rod for the lever. The lever is made of aluminum, and its
diminution is (6x1x3/8 in). The lever is attached to the connecting rod by a removable stainless
steel push pin. Lastly, two aluminum sheets, which they have dimensions of (6 in) in length, (4
in) in width, and a thickness of (1/8 in). Also, there is a (1 in) diameter hole was drilled at the
center of each sheet (Figures St 1.4 and St 1.5).
The entire system is easily attached to the frame by inserting the connecting rod through the
holes in the aluminum sheets, and then connecting the lever on top. We are able to secure the
aluminum sheets to the frame by using two 3 in. stainless steel bolts and matching wing nuts.
Figure St 1.4: Rudder Guide Plates.
48. What we would do differently:
After we completed the project, we went to nearby lake to test it. We noted that there is an issue
within the steering system; although the rudder to rotate easily, we have difficulty in navigating.
We found that the lifting force on the rudder plate is not enough to steer the vessel. This problem
can be solve in three ways; by increasing the vessels speed, so that the water flow increases and
generates more lifting force, or we change the rudder design to have a bigger area or by adding
additional rudder. By doing so, we will increase the area, which will lead to generating the
require amount of the lifting force. On the other hand, we noted that the navigation will be more
comfortable if we change the position of the steering system which is currently located between
the driver legs. An idea that we came up with was if we were to move it back between the rear
sponsons.
Figure St 1.5: Drilling the holes for bolts. Figure St 1.6: Rudder attached to frame.
49. Final Budget and Cost:
Drivetrain:
PARTS DISCRIPTION QUANTITY $ COST
Idler Sprocket for # 25
Chain
1/4" Pitch, 3/8" Bore 2 $ 49.46
Roller Chain # 25 1/4" Pitch Per ft. 8' In
Length
1 $ 42.12
Sprocket for # 25 Chain 1/4" Pitch, 10 Teeth,
1/4" Bore
1 $ 10.53
Sprocket # 25 Chain 1/4" Pitch, 45 Teeth 1 $29.39
Mountain Bike Bottom
Bracket
11/2" Aluminum
Tubing 3 ft.
1 $ 29.99
Tube Mount 17" 1 $ 21.82
Ball Bearings N/A 1 $ 12.00
Crankset N/A 1 $ 25.00
Plastic Pedals N/A 2 $16.99
Pins N/A 4 $ 12.00
Chain Tube 2x2" 3' 1 $ 27.94
Solid Aluminum Bar 12" 2x1.75 1 $ 7.00
Plate For Drive Mount 3/8 1 $ 17.00
Total: $ 301.24
53. Conclusion:
Our final specifications were as follows:
Final assembled weight of under 200 pounds
14 ft. in length by 7 ft. in width
Disassembles into 9 pieces (two people is optimal for ease of assembly)
Front member Seat
Two rear members Drive
Three sponsons Rudder
Approximately a total of 135 US gallons of displacement
Approximate maximum speed of 5 knots
Propellers are optimized for thrust in one direction of rotation. Despite the theoretically higher
efficiency when in forward than in reverse, comparable speeds were reached when reversing to
those reached when driven forward.
The 135 gallon displacement provides a sufficient safety factor to allow three occupants on the
boat. Due to the seat’s centroidal location, the weight is distributed very evenly across all three
sponsons.
The entire boat is easy to put together and take apart. The process is made especially convenient
when two people are assembling simultaneously. No single piece is unmanageably heavy, and
the entire boat is under the weight target of 200 pounds.
With a reasonable maximum speed of five knots and effective reverse mechanism, this portable
and easy-to-disassemble boat fulfills our client’s needs.
