Check the archives for a thread involving Sam McFadden and vac bagging. He said it's a tightwire balancing act. Pull too much vacuum too early, and the cloth is starved. Pull too little too late and you lose the benefit. It works much better on multiple layers than on singles. I'm not convinced that you will be able to get your full-depth, finished epoxy coat in one shot this way. Let us know how it works, OK?

: OK, I'm about to start construction on a CLC North Bay XL, and I need some
: advice. My first S&G effort (Ches. 18) weighs as much as a battleship -
: too much epoxy, needless extra glass. On the new boat, I'm on a huge kick
: to reduce weight without compromising strength, so I'm looking into vacuum
: bagging. Here's my plan - fire away!

: 1. Stitch hull as normal using microballooned fillers and a sheer clamp made
: from ceiling moulding (the coved kind... can you imagine this?), and
: pulling the copper wires. So, I guess that's not normal, but nothing too
: whacky yet.

: 2. Seal the inside surface with thin coat epoxy, sand lightly.

: 3. Carefully tape heavy-duty painter's dropcloth (5 mil? 10?) to the inside
: of one side of the hull. (Duct tape - the handyman's secret weapon!) Wrap
: cloth over the boat, trim to shape so it wraps onto the opposite, inside
: surface of the hull. (This is the vacuum bag.) Pull plastic back over,
: exposing the wood. Also prepare individual plastic sheets cut in exact
: shape of the panels. (These are the barriers between the glue and the
: breather layer.)

: 5. Glass outside with 4 oz. satin-glass w/ extra layer on bottom.

: 6. Carefully lay down the barrier layer. Stick the breather layer (maybe
: cheapo felt from a fabric store?) down with double stick tape, maybe a few
: spots of 3M 77?

: 7. Wrap the plastic back over the boat, tape it down.

: 8. (If you're not laughing yet, here it comes...) Stick a shop-vac hose into
: the bag, tape it up as best as possible, and let 'er rip.

: 9. Roll out as much epoxy as possible - I think it should only take a couple
: of hours before the vacuum has done its work.

: The whole point of this is to avoid the second and third coats of epoxy, as
: they do nothing for strength, and only add weight. Please offer your
: critiques, suggestions, jibes even... I'd really appreciate it.

: And if you think this is nuts, just wait to see what I do with the deck!

: Nathan