Thursday, December 13, 2012

Pit Bot- Making Of: Part 2

Pit Bot: Carbon Fiber

For the exterior shell of the torso and a few other parts i wanted to have a carbon fiber look to them, after some research I decided to do it for real and visited a family friend who runs a canoe and kayak center where he makes carbon fiber paddles. After a quick demo I bought the required materials and scampered back to the workshop. What follows is the process involved.

a rough pattern for the torso shell is layered down with masking tape, the tape prevents the fiber from fraying when cut with a scissors

you can see in this image the plaster carving of the torso shell has been covered in a semi hard foam board, it bends when heated and is very solid when cool. using a heatgun you are able to shape a flat piece of this 'Thermo flex foam' and shape it around your plaster shape. this will form the base material of the carbon fiber, sturdy and very lightweight.

next step is to mix the epoxy resin, if i remember correctly it was a mix ratio of 1:3.
then using a clean layer of plastic underneath your fiber, pour the epox directly on top of it..

after pouring your resin then begin spreading it on the fiber, like buttering a piece of bread..

then you lift the soaked fiber sheet and begin smoothing and shaping it onto the foam. the resin soaks into the foam and creates a very strong bond.

while the resin is still wet the next thing that goes on is a layer of nylon fabric called Peel-Ply.
this fabric basically soaks into the resin and pulls it up away from the fiber, so that the fiber is trapped in a layer of resin between the foam and the peel-ply. the reasons for this are apparent soon..

once the resin dries you then rip the peel ply away, the peel ply does not stick well to the surface but it creates a slightly raised even texture on the dried resin which is easy to sand down and polish. without the peel ply, the resin would settle on the top of the carbon fiber and there would be no allowance for sanding without sanding down into the actual fibers themselves. below is rear torso panel dried with Peel-ply still on..

and here is the same panel with the ply removed

then after a few hours of sanding with wet and dry sand paper you have a very smooth finish.

More to come in Part 3!!

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