jetpack

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I am a model powerboat builder. Our kits are built out of usually three-ply mahogany or birch ply. Boats are built like an empty paper egg crate dividers with full length parts and bulkheads.

The ply thickness used to for these is usually no thicker than 1/16" or 1/8", and usually warped and very coarse grained.Typical building techniques have you build the entire hull except for adding the deck, and seal the whole inside with epoxy for waterproofing.

Some of the parts, such as the cockpit sides inside the boat is what you will see when it it finished. Using epoxy on this type of wood raises the grain, does not completely fill, and is very difficult to reach to sand.

My idea is to "pre-coat" the parts before building with epoxy, using two large thick shelf glass you can buy for the home.

I have read a really good suggestion for a fiberglassing technique using PVC Vesqueen sheet housing plastic used for vapor barriers, ect. in house construction for glassing large, flat areas and having it come out smooth with none or very little sanding.

You spread a thin coat of fiberglass resin (it would be epoxy in my example) onto the sheet plastic, lay down your fiberglass onto the wetted plastic, wet the part to be glassed, and then apply the plastic to the part, then squeegy it out flat and let it cure. Once cured, you peel the plastic off and you are left with a perfect surface. The plastic does not stick to the cured resin, and leaves the resin with as good of surface finish of the plastic.

I was thinking of doing this to my boat parts, using the technique but instead just staying with epoxy and no fiberglass, and sandwiching the parts between the two pieces of plate glass shelving.

My question is will this help hold the parts straighter, when the epoxy gets a chance to soak into the wood and cure, and will it leave a nice smooth surface?

I realize there will be run off on the sides of the part that will have to be sanded down, or perhaps stringer notches re-opened on the bandsaw, ect. to get everything to fit again. The outside sheeting could benifit from this also if it is a good idea - inside corners would require no sanding, and I would be starting with "smooth" prefinished wood.

I am not sure if this would gum up bandsaw blades, or fill disk sanding pads past what I am willing to deal with, keep the parts straight, or add unwanted thickness to the parts that would affect it dimensionally through the build.

I would like to hear peoples ideas on this !

Thanks everyone...

I included a couple of pictures to help demonstrate the "unreachable" inside cockpit sides, and another of an old hull to show the thin ply sheeting of the bottom surfaces where it would be nice to have pre-finished before glue-up.

daven

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I've used that technique with fiberglass and mylar sheets (.014 thick) and then placed in a vacumn bag. You can get a very good finish that way. You can even primer or paint the mylar prior to laying up the glass and it will transfer to the finished part.

You need to wax the mylar well. Maybe you could use lighter ply and use fiber glass for the extra strength??