The stock cowling cannot be used on the modified snowmobile due to the under hood clearance issues b

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COMPOSITE COWLING DEVELOPMENT DIVISION
Material Choice
A number of material options exist for hood
reinforcement. Fiberglass was previously used as
it is cheap and relatively light weight. Carbon
fiber and Kevlar are other options available,
too. Due to the stiffness driven design for the
part, carbon ended up being the logical choice as
it has a higher modulus in comparison to other
available materials. Once we had determined
carbon fiber was the material of choice, we still
needed to determine how many layers and of what
orientation fabric to use. A simple test was
devised that enabled us to test the endurance of
the carbon fiber in bending. A lever arm was
attached to one end of a sheet of carbon fiber,
with the other end attached to the stock style
hinge mechanism on the sled. With a weight to
simulate the hood attached to the end of the
lever arm, it was cycled 100 times and checked
for any signs of cracking. This test proved that
two layers of carbon are the optimal number of
layers for this application.
Motivation
The stock cowling cannot be used on the modified
snowmobile due to the under hood clearance issues
brought on by the addition of emission control
hardware. Two replacement hoods have been built
previously and yielded mixed results. Neither of
the hoods looked particularly appealing, and both
had fitment and performance issues.
Goals
This Years Achievements
Group Members

• Improve quality of hood
• Decrease overall weight of hood
• Improve rigidity and optimize fiber orientation
• Increase hood clearance over previous years

It can be seen in the pictures that this years
cowling is a drastic improvement over previous
years and even over the original stock cowling.
This years hood was designed to better clear the
muffler under the hood, while simultaneously
improving looks and helping the fitment. The new
cowling has a far more impressive appearance,
boasting the carbon fiber look with custom air
brushed graphics. As expected, overall rigidity
is up due to the material strength gained by
choosing carbon fiber over glass fiber, and the
increase in the total amount of material that
makes up the cowling. This years hood did not
show a significant weight decrease because most
of the time had to be spent on creating the mold
and learning the proper fabrication procedures.
Learning the proper procedures helped ensure
professional quality.
Matthew Bodwell Christopher Hill Evan
Merritt Jesse Morin
Processes
This years hood was made using a three stage
process. The first stage was to create a plug in
the desired shape of the hood. This was made
from a rough shape of plywood and foam, which was
then covered with a layer of Bondo to smooth and
create the final shape. The next stage of the
build was to create a female mold of the hood out
of fiberglass. We took the male plug we had
made, applied paint and a release agent to it and
carefully laid many small layers of fiberglass
over the plug. This gave the mold the shape of
the plug while enabling the fiberglass to take
the shape of the plug with minimal
deviations. Once the hand lay-up of the mold was
completed, a practice hood was made. We used the
SCRIMP resin infusion process for this. This is
a vacuum process that pulls the resin over the
surface of the material, eventually fully
infusing the fabric evenly. It gives a closer to
optimal fiber-volume ratio while reducing void
spaces. Once we had established a working
process, we made the final hood out of carbon
fiber and had it gel-coated and painted by a
local bike shop.
Future Work
The new mold will allow future teams to
concentrate on more in-depth stress analysis and
lay-up optimization. A more highly optimized
design will better utilize core and reinforcement
materials that will allow the overall strength
and rigidity to remain at current levels while
weight is reduced. Weight reduction using modern
materials will remain a focus of the Maine Clean
Snow Mobile Team.