Best thing to use as a fiberglass form?
 

I want to make some brake hose ducts to fit in the place where fog lights would typically go in my valance.

Anyone have any good ideas of what I can use to form the proper shape and make a fiberglass form out of?

Thanks!

-B

How many peices will you be making?

Try carving the form out of styrofoam; then finishing it with a coating of plaster to get a hard, smooth surface.

foam with plaster on top for a smooth surface. then coat the plaster with about three coats of shellac mixed 1:1 with denatured alcohol as a water barrier. then spray two or three healthy coats of PVA, poly vinyl acetate (parting agent) and then a nice coat of gelcoat. black gelcoat is easy to work with as you can see it cover your mold and also when you lay up the fiberglass it is easier to see if you have any bubbles or dry spots in the fabric. best of luck, im guessing your going to use a 2 piece mold.

Thanks guys! I'll be making two pieces. Since the form would be semi cone-shaped, I would hope to be able to pull the form out of the fiberglass shell when done and avoid needing a two piece mold.

I prefer Bondo to plaster, but I don't know if the Bondo will eat the styrofoam.

You can get some ducts to fit there from Pegasus which are very reasonably priced. In case you want to save the hasle.

Juan

Thanks Juan. I have actually purchased and returned a few different ducts because non of them fit. I have the 930S valance from BetterBodies and even they do not know of any ducts which will fit....

-B

You can make a male or female mold depending on which side you want the finished side to be. You can make a sacraficial mold out of styrofoam and covered with plasic strips or dipped in wax or plaster (then shellac). You can lay up your glass mat directly and then dissovle the mold from within after the part has completely cured.

You can make a mold out of tooling clay and remove it with low heat. I have layed up glass right on clay before to make a mold from which I made a part. It's easier to use plaster and burlap for that process, but either one works.