[simpits-tech] I need to make some parts out of

[Bubba]

Marc Quintin wrote:
> Fiber glass, the parts have a irregular top of a 1/2 boxe kind of
> shape 10''X9''X1'', one side at 2''. So I'm in the process of making
> a mold but I'm not sure what to use, I was thinking of  fiber glass,
> plaster of paris or latex. I would prefer latex but I'm not sure how
> it will react during the curing process of the polyester resin

Ok, I'll get off my butt and answer.

First, which side is the good side? Inside or out? Do the corners have to be 
sharp? Is it structural?

2 ways to do it, off the top of my head:

1- Make a male plug out of, say, 1/4" MDF glued with Probond, sanded smooth 
(and then sanded some more), and seal it with a few coats of polyurethane, 
sanded until you can't take it anymore, and polished with a dozen coats of 
car wax. You'll need a couple of degrees of draft on the sides to get the 
part off the plug and building in a hose nipple in the middle of the big 
side wouldn't hurt. Seal the nipple with a piece of thin tape, lay up the 
glass, and hope it sticks to the mold. If it won't stick down to the sides 
try laying it up then putting the plug on the floor, cover it with a garbage 
bag, then fill the bag with about 10 gallons of water to force the bag 
against the mold, trapping the glass in the middle.

2- Make a female mold, basically as above, and use the water bag trick.

If you wanted to get really nuts you could build both a male and female mold 
with about .075" between them, fill the mold with dry glass, and inject 
resin into the middle of it (resin transfer molding).
-- 
Steve
mysticz28 at swbell.net
He who seeks will find, and he who knocks will be let in.