hnesitd1

Hello Gents, Recently I acquired a partially constructed bi-plane model from my father. The problem is that an engine cowl needs to be constructed. From the plastic original I was able to make a female mold from plaster-of-paris. I need advice on the best way, using the mold, to fabricate the cowl with fibreglass, lightweight cloth. I would like to use epoxy resin (no smell,eh?). Any advice. Will the cloth take the female mold's shape?

Ed Smith

If you have a raw plaster of paris mold you must seal the mold surfaces before you use it. If you do not the cowl will not release. I seem to remember shellac being used for this purpose. I would suggest sealing it with epoxy resin first and then painting. Whatever you do ensure the mold surface is non-porous and will accept a mold release.

Ed S

hnesitd1

Thanks Ed. After sealing do you think the lightweight fiberglass cloth will follow the inside contours of the female mold?

Ollie

If you use very light weight cloth it will go around very tight curves, it drapes so easily. You just have to use enough layers to give you the strength and stiffness you want. The thickness of 1.5 ounce fiberglass cloth is 0.002 inches. Let's say you wanted a cowl 1/32 of an inch thick or 0.03125. Just use 16 layers of 1.5 ounce cloth. It will have about the same strength as one layer of 24 ounce cloth but will be far smoother.

hnesitd1

Thanks Ollie. Fitting the 2 ozs cloth dry it wrinkles a bit at the front of the female mold - is this a problem. Will the cloth, "lay down" when soaked with resin? I'm hesitant to start this until I've tried to cover every eventuality of what might go wrong.