Nick,

I had another idea for a poor man’s vacuum bag technique that might avoid some of the problems you are talking about.

I have always been fascinated with shrink plastic that is used to seal windows in the winter or the heavy duty stuff that is used to winterize boats. The stuff seems to shrink in all directions removing wrinkles and providing a fair amount of pressure. It seems that you could accomplish the same thing as a vacuum bag on the outside of the hull by wrapping the peel ply and bleeder sheet in shrink wrap and shrinking it with a heat gun.

With this method you are not drawing air out of the wood or leaving it in an evacuated state that could draw in water in the future.

The only problem I could see is that the heat to shrink the wrap would set off the epoxy too fast before the pressure would bleed out excess epoxy or do it’s job. As far as doing the insides vacuum bagging seems to be the only way to do a concave surface.

Any comments?

Jack

> I haven't done it yet, but I do intend to try eventually.

> One thing you need to watch out for is if you do a "wet" layup -
> wet out the glass then cover it with the bagging - you will draw air out
> of the wood. This air will need to pass through the glass and epoxy in
> order to be withdrawn. Chances are very good that you will get air trapped
> in the resin. A "better" way may be to do an infusion - bag the
> boat with the glass laid in place dry and draw your vacuum. Puncture the
> bag in a few places and hook up tubes to the punctures so the only opening
> out of the vacuum is through the tubes running to a bucket of epoxy. In
> this way the epoxy is drawn into all the cavities and presumably no air is
> trapped.

> The difficulty is if you create an "island" completely
> surrounded by epoxy with no effective bleader to the vacuum pump you can
> still get trapped air. But with care this can be avoided.