You have so much substituioon of parts that this is beginning to sound like some kind of badly mixed recipe.

: 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.

OK, let's deal with that part first. You have a lot of details to share with us:
How many gallons of epoxy did you use?
Did you use a sealing coat?
What weight of glass for taping seams?
What weight of glass for sheathing hull and deck? Did you glass deck?
Did you glass interior?
What thickness of wood?
What kind of wood?

: 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!

Vacuum bagging is not a guaranteed way to "reduce weight without compromising strength" It should reduce the weight a bit, but there may be some compromise in strength. Wait, let me correct that. There is ALWAYS some compromise in strength. you just want ot be sure that ou have sufficient strength and that whatever you trade to get this is not too big a matter. Your choices are usually weight or dollars. If youwant more strength you add glass (dollars and weight) or go to a stronger, lighter fabric for reinforcement ( dollars and weight). You are proposing to simply cut down on the excess resin, which will save dollars and weight, but you don't need to vacuum bag for this. Changes in technique and additional sanding can also work for you.

: 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.

The ceiling molding is going to be made from a hardwood like maple, birch or oak. You can save a few ounces, and a few dollars, by cutting your own from cedar boards. You get a considerable amount of strength from the sheer chine. You don't want to make it too light.

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

Do you plan to glass this later? Going with a layer of glass on both inside and outside will give you atronger constuction than just sheathing the outside with glass. This should allow you to use thinner, lighter wood panels. You could go to say, 3mm from 4mm for a 25% reduction in the weight of the wood. If you glass the interior you can leave off one layer of heavy tape on your fillets, too, giving smaller, lighter fillets.

: 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!)

Are you doing just the hull? (No deck on yet?) Get a roll of 4 mil 10' by 25' polyethylene at the hardware store or Wal-mart for about $10. Open it up and then fold in half, giving you a 5 by 25 shape. Tape the long edge and one of the short edges, and, when you are ready, slide the boat in through the open remaining edge. No cutting and one seam is taken care of by the fold. Alternately, place half the palstic on your building table, lay the boat on it, and after applying the glass and resin, fold the plastic over and seal the edges as above

: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.)

You want to get real peel ply. If you try making your own you risk geting those palstic sheets glued permanently into your boat. And you put this on AFTER you apply the glass and resin.

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

OK, now you cover the thing with peelply and a breather layer. The excess resin is forced through the peelply and absorbed in the barrier, which should not stick to your boat as the peelply forms a parting barrier

: 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?

I'd be afraid of ending up having a boat with fur on it if I used felt. It sheds a bit, and at the wrong time. If you want to do this, go for the right materials.

: 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.

Shop vac may actually be a very expensive way to do this. The device is very powerful and will certainly pull a good vaccuum, but the motors on home vaccuum cleaners are not designed for continuous duty when pulling a near total vacuum. Unlike a vacuum pump. Once you get the bag sucked up tight there is no sir left to flow through the deivce to cool the motor. You can feel the drop in air flow by holding you hand near the air exhaust. With no air flowing through the shop vac there will be no air to cool the motor. You might get away with this once or twice, but you might also burn out the motor. Vacuum pumps don't get cooled by the air they are sucking in, so they can take continous use, even when they are sucking a vacuum. If you use a shop vac, connect it with some excess material that you can seal to hold in the vacuum, and then you can turn off the shop vac. This won't give you as much pressure (vacuum) as a vacuum pump but if you turn the motor on and off at intervals, and your methods of sealing the bag is good, then you might get sufficient vacuum and still end up with a shopvac that works.

: 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.

Do a small test panel at the same time and keep checking that. when the epoxy on the test panel has set up you might as well unplug the vacuum. The resin may still be soft and green, but it won't go anywhere.

: 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.

Well, they also fill the weave of the fabric, giving a slick surface with less water resistance. Imagine if you will a magnified view of your hull with one coat of resin on the fabric. the weave is plainly visible, with each strand showing as a half of a cylinder. Lots of hill and valleys. Now the wetted surface area of this is going to be the total of all those hills and valleys. If each fiber shows up as a cylinder, then for the width of the fiber the circumference of it will be the diameter of the fiber times pi ( 3.1417...) and for all those half cylinders of fibers your roughly finished glass job will have about 1.6 times the wetted surface area of a smooth finish. That can be significant. It will cut your glide and require more paddling effort. The smooth finish is better.

Ok, so how do you get a smooth finish with less effort? And less weight.

One idea that has already been proposed is to go with lighter cloth and sand back into it. That is half good. If you leave that unsealed then water will eventually wick into the microscopic spaces around the exposed glass fibers, and your resin will be slowly damaged. Might take 10 to 15 years for this to happen, though. Just using thinner cloth will give you a finer weave and therefore lower hills and valleys to fill. you may get by with a single light fill coat on 2 ounce or 1 ounce cloth. You get the strength of 4 ounces of glass with 2 layers of 2 ounce cloth, but you get a finer surface finish on the lighter cloth.

Personally, I'd hit Defender for some 2 ounce cloth, (www.defenderus.com) and probably qualify for the 25 yard discount. One or two layers inside, and two or three layers outside. 8 ounces on the bottom is probably more than needed. You'll have some scratches there from wear and tear, but unless you get frequent penetrations, 4 to 6 ounce fabric should be adequate. Besides, you can always add another layer or two on the highest wear spots later if your boat shows that it definitely needs it.

If you are working with 2 ounce cloth, try this technique: cut your panels and apply a "starved" coat of resin to seal the wood pores. Let it set up. Then, lay on a single layer of 2 ounce cloth on the inside of the panel and affix it with the minimum of resin. Do this while the panel is flatso the resin can't dri or pool. Use a squeegee to get the glasswetted, and then to scrape off any excess resin. Through out what you scrape off. When the resin is set, lightly sand the panel, which should be easy as it is flat, and then drill, stitch and assemble as usual. You cna seal the outside while the panel is flat, too, and if the material s thin enough, you cna put on a 2 ounce layer of cloth, too. Working with thick materials and heavier glass may make it more difficult to pull the panels into alignment on assembly. Once you av the thin layer of glass on the plywood, your scarfs are reinforced, and you have a smooth base for the next layer or two of thin cloth and resin.

Hope this helps.

PGJ

: 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