: Other than the obvious expense,

Expense is obvious?

Face it unless you can get the fabric for free, whether you cover the boat with kevlar, or cotton, you gotta pay something. Subtract the cost of a canvas covering from what you pay for the kevlar and you may find the difference is not too bad.

: is there any reason that kevlar cannot be
: used to cover a skin on frame canoe or kayak?

A lot more depends on the strength of the fabric, not on the chemical makeup of the fibers. A very thin piece of kevlar, say something in the 1 ounce per square yard or lighter range, might not be as strong as a piece of 20 ounce nylon, polyester, or fiberglass.

At the same time, consider that the thickness of the waterproofing material might depend on the thickness of the fabric on which it is applied. A piece of cotton duck that is .08 inches thick and is saturated with a rubber compound will give you a rubber layer that is also .080 inches (80 thousandths) thick, while a superstrong synthetic which has the same strength as that cotton duck maight be only .010 thick (10 thousandths). If you saturate the thinner fabric and have a rubber layer that is only .010 thick it might be more easily abraded, or perforated. If that happened then although the fabric doesn't rip, you would get lots of pinhole leaks. You could keep applying the waterproof coating to the surface of this material, and build up a thick coating, but the additional layers of rubberized material would not be reinforced, so there would be no increase in strength, but the weight would come close to that of the cotton duck covering.

So, Kevlar is good if it is strong enough, and thick enough. Don't buy the thinnest you can find unless you are looking for a special purpose, extremely lightweight, and rather delicate boat. Are we thinking a backpacking boat here?

Assuming it is ok to cover a
: skin on frame canoe or kayak with kevlar, do you wet out the kevlar like
: you wet out fiberglass?

It should be simpler. Since there is no wood structure under it, you don't have to worry about forcing the resin through the fabric. There is no underlying wood to act like a sponge and suck away the resin, either. A roller would probably put on a nice even coating, which would soak into the fibers and weave. I'd just paint the resin on, and then go to the inside and brush away any drips I could reach with a (mostly) dry foam brush.

It might be worthwhile to try a sample first. If you can coat the interior surface of the cloth before attaching the skin you would have a stiffer material to work with, but the inside would be completely covered. applying that stiffer material to the frame you would need to slit it in several places to get it to follow the lines of the boat, but these cuts could be overlapped and glued with epoxy resin, and reinforced with an additional strip of your kevlar and resin.

The kevlar should go rather clear, and probably somewhat yellow in color. Carry your gear is brightly colored gear bags and it should look rather pretty. Or, add a pigment to the epoxy resin.

As long as you are using epoxy resin, coat the frame with 1 or 2 coats and let it setup for a few days before you cover it.

You may want to coat the boat with a UV blocking varnish if you have not added solid pigment to the epoxy resin.

hope this helps.

PGJ