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. Motivation 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. The stock cowling cannot be used on the modified snowmobile due Once we had determined carbon fiber was the material of choice, we to the under hood clearance issues brought on by the addition of still needed to determine how many layers and of what orientation emission control hardware. Two replacement hoods have been built fabric to use. A simple test was devised that enabled us to test the previously and yielded mixed results. Neither of the hoods looked endurance of the carbon fiber in bending. A lever arm was attached particularly appealing, and both had fitment and performance issues. 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 Goals that two layers of carbon are the optimal number of layers for this application. •Improve quality of hood Group Members This Years Achievements It can be seen in the pictures that this years cowling is a drastic •Decrease overall weight of hood improvement over previous years and even over the original stock •Improve rigidity and optimize fiber orientation Matthew Bodwell cowling. This years hood was designed to better clear the muffler Christopher Hill under the hood, while simultaneously improving looks and helping •Increase hood clearance over previous years the fitment. The new cowling has a far more impressive appearance, Evan Merritt boasting the carbon fiber look with custom air brushed graphics. As expected, overall rigidity is up due to the material strength gained by Processes Jesse Morin 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 This years hood was made using a three stage process. The first to be spent on creating the mold and learning the proper fabrication stage was to create a plug in the desired shape of the hood. This was procedures. Learning the proper procedures helped ensure made from a rough shape of plywood and foam, which was then professional quality. 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. Future Work Once the hand lay-up of the mold was completed, a practice hood The new mold will allow future teams to concentrate on more in- was made. We used the SCRIMP resin infusion process for this. depth stress analysis and lay-up optimization. A more highly This is a vacuum process that pulls the resin over the surface of the optimized design will better utilize core and reinforcement material, eventually fully infusing the fabric evenly. It gives a closer materials that will allow the overall strength and rigidity to to optimal fiber-volume ratio while reducing void spaces. Once we remain at current levels while weight is reduced. Weight had established a working process, we made the final hood out of reduction using modern materials will remain a focus of the carbon fiber and had it gel-coated and painted by a local bike shop. Maine Clean Snow Mobile Team.
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