molding carbon fiber?
 

I started this thread on private message board, got some info, and I'll quote everything, because there's lots of good information, but I'm still looking for everyone's opinion. I've got NO experience w/ any of this, so any help's greatly appreciated.

I really have nothing to offer as far as the how-to is concerned, but after all that work and expense of making a one-off, I wouldn't want to drive it! I would cry after landing from the first jump and scratching the bottom up. :cry:

Good luck and keep us posted on your progress!

I don't have any advice for you on the mold. I'm using aluminum, but that would be nearly impossible for your rendering. You do have to remember that the finish of the mold will dictate the finish of the composite.

As far as vacuum bagging goes, the hot budget setup is to use a Foodsaver (or similar). A brand new one will cost less than $100, and they're available used in almost every flea market or swap meet for dirt cheap. They pull a good vacuum in a well sealed bag. Do a Google search for such, and you will pull up a couple excellent articles for using one. The articles are aimed at the model rocket crowd, but it all directly applies here.

I've been learning vacuum bagging from a RC cargo airplane team/research group, where we have a foam wing that we lay uni-directional carbon fiber and bi-directional fiberglass onto to increase strength (the 100" wing has to be able to support 40+ lbs).

If you want to reuse the mold, you'll have to wax it before each time CF is layed down. The wax needs to be rubbed in really well, as any minor chunks will show up on the finished product (like pb4ugo mentioned, the mold surface needs to be smooth).

The usage of a fabric ("batting") is to hold the excess epoxy, so it doesn't get into the vacuum pump.

That website linked to on the first post has thicknesses listed for the carbon fiber fabric:
http://www.uscomposites.com/carbonpage.html
The thickness you use I would think should depend on how many layers you want to do. The thinner the fabric (the lower the weight) the more layers you'll have to have. But I bet if you have too few layers, it won't be strong enough.

Actually designing the mold will be the hardest part IMO. I was thinking clay would work, but then I remembered that clay shrinks as the water in it evaporates. But if you could account for that shrinkage, then I suppose it'd work.

I want to try vacuum forming some CF or fiberglass as well, since I have access to mylar (vacuum bag material), fiberglass cloth, epoxy resin, a vacuum line, and the appropriate wax.

I have an automotive a/c vacum pump, it can pull a closed sytem down to 30" of mercury. Would that work? I think it is a 2.5 cfm. I would almost like to try this with fiberglass as I have years of experience in laying that up wet. Maybe I will make something, like a custom chassis or body or maybe a boat hull, any ideas what you guys would like to see?

real quick, i want to say i feel like an idiot for not seeing the thickness of the cf on that page :(

Boat Hull would be kick A$$

A fellow rc'ers father showed me how to make carbon sheets. It was rather easy once he showed me. He had done fibreglass stuff and made boat hulls and such. It was always interesting going over for a chat and listen to him describe the methods and such. He explained a product he called peel and stick. it was a porous material for doing the inside of the hulls. they made a mould for the outside that used release wax and the inside this peel and stick stuff they squeeged the excess out. it left a rough finish inside though so you might not get the desired finish. I wish he still lived down the street so I could toss this thread at him to comment. he's retired and living up country now