Keep your fillets to a minimum, use only four ounces of epoxy in each end pour, and don't fill the weave on the interior, and you can meet your weight goal. The added weight of the second layer of cloth is negligible and not worth the trade-off in strength and abrasion resistance. My slightly larger Merganzer 17L hybrid came in at 41 pounds. -Wes

a light build is a matter of collecting a number of savings all of which add up.  a couple additional tips:

-   pre-pour your end pours so you strictly control the amount of material/weight used.  some people carve a light piece of wood for the end pour and attach it with very thickened expoxy with microballoons.   you can cut the weight of end pour by 1/2 and still get the strength you need and the ability to drill a hole that does not put a hole in the hull.

- pre-coat the wood with a thin layer of epoxy before glassing.  this prevents the wood from absorbing a lot of epoxy during the wetting out process.

- use painters tape to help you keep your fillets to a minimum...this will help you control the width of the fillet.   make sure fillets is not too wet....right amount of wood flour will keep it light.  too much epoxy just gets heavy.

- very careful epoxy work, clean up all spills and excess....particularly on the interior where you otherwise would not sand it off (similar to note above - do not fill the weave on the interior).

Here's some rules of thumb

A good layup is approx 1/3 glass, 2/3 resin/hardener.

Glass/resin/hardener weight approx the same as water.

Glass weighs approx the same as resin/hardener.

Glass weight is ounces per sq yd in the US (caution - may be one of the funny yards, like sailmakers' yard, which is not the same as 3 ft by 3 ft. Sigh, why aren't we metric?)

So putting all these together, skipping a 4 oz layer of glass should reduce the boat weight by approx 12 ounces per square yard. The actual decrease will depend on the builder's skill.

If the glass was on the outside, the boat will float on approx the original waterlines.

Have fun,

Laszlo

Thanks all for a lot of good suggestions.

Any comments on using cloth other than fiberglass in the cockpit?

What's the best application method for precoating the hull before fiberglassing?

My CH16 build last year came in at 44lbs. I probably used a couple of pounds of Brightsides on the hull.

for precoating the hull, use a plastic epoxy spreader (see the clc site product catalog). 

these are basically large pieces of bendable plastic, (similar to a credit card) that can be used to quickly and evenly apply a very thin coat of epoxy on the plywood.

all you are trying to do is wet it and then immediately wipe all the excess off.  this creates a barrier to further epoxy absorption that is lighter than would occur compared to wetting out the glass on raw wood.

if you apply the glass cloth within 24 to 48 hours after this application, no need to rough it up.

the spreaders are also extremely handy in wetting out the cloth and getting thin, even coats of epoxy.