Filler for Foam Fiberglass Forms

[szicree]

How do you like that alliteration?? So what is the preferred material for smoothing out styrofoam prior to applying glass layups. I'll be throwing away the foam afterwards. Thanks.

[tcone1]

Packing tape works well, and releases very nicely if waxed.

Tim

[DanH]

Tim is right; packing tape works great, if the part is mostly flat. Compound curves will give you some wrinkles and bumps. I'm using red tape in the photo below; that's a biplane cabane fairing.

If the desired part is all curves, coat the foam with any easy-sanding cheap filler. Plain old drywall compound will work. Seal it with a few coats of paint from a rattle can, wax it heavily, do your layups, and dig out the foam from the backside.

Time spent shaping the male mold precisely pays back later when you're finishing the final part.