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.

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.

Motivation

Goals

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.

This Years Achievements

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.

Future Work

Processes

•Improve quality of hood

•Decrease overall weight of hood

•Improve rigidity and optimize fiber orientation

•Increase hood clearance over previous years

Material ChoiceA 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.

Group Members

Matthew Bodwell

Christopher Hill

Evan Merritt

Jesse Morin