Making your own composite parts: looking for tips

[Kevin Sevcik]

Originally Posted by tcj103

This year our team scored some pre-preg carbon fiber material that was destined for the dumpster.

Ted,

I don't like being a party pooper, but based on the rules last year, I think you need to do a little research on the pedigree of your carbon fiber before you consider using it on your robot.

Specifically, anything you use on your robot has to be (reasonably) commonly available to all teams to purchase. If your brand of pre-preg isn't commonly sold to the public somewhere that has a reasonable amount of stock on hand, then it's not legal for use on the robot.

Moreover, you have to account for the cost of your carbon fiber in your cost accounting, whether or not you paid full price, 90% off, or saved it from the dumpster. The upshot of last years rules is that you're either allowed to use the fair market value of the entire amount you bought, or a quasi-prorated amount that's probably almost always less. Quasi-prorating means you're allowed to use the price of the smallest amount you could actually buy that would cover the amount you actually used. No finding a unit price and multiplying by the amount you used. So if carbon fiber comes in rolls of 100 sq ft for $500 and 20 sq ft for $150, and you buy a 100 sq ft roll but only use 10 sq ft, then you can use the $150 price of the 20 sq ft roll in your robot BoM, but it's the full $150 that you account for.

This is an important rule because you only get $3500 total to spend on your robot. And much more importantly in this case, no individual component can cost over $400. In the above example, if your carbon fiber only comes in $500 rolls, then it's not legal to use.

Again, this is all according to last year's rules and things might drastically change, but I think it'd be a good idea if you found out the specifics of the carbon fiber you have and whether it or something extremely equivalent is available to other teams at a legal price.

As for a filler material, I'd consider stacks of insulating foam, machinable foam, and possibly even a light wood like balsa or a red cedar.