While the shrinkwrap material should keep the water out -- and be rather easy to repair with duct tape should it rip -- you should consider a cloth liner to keep abrasive grit and dirt away from it. You can use a thin, lightweight polyester or nylon fabric which is just stapled to the hull's sheer chine before you apply the shrink wrap.

Depending on how you are assembling the frame, and where you put the staples, the liner fabric may also serve to keep the pieces in assembly order when the boat is disassembled. I suppose it is even possible that you could fold up the wood parts and roll the extra fabric around them. Add a couple of tie strings and you've got a cloth-padded bundle, and no need for a storage bag for the parts.

The fabric does not have to be waterproof, or even water repellent. It is primarily there as a dust trap. BUT, if you coat it with a couple layers of waterbased polyurethane it just might serve as a water barrier should the shrinkwrap get a really nasty tear. While the fabric will probably not be as tight as a kayak skin usually is, if it keeps you afloat until you can make land and repairs can be made, you'll appreciate having it there.

If your shrink wrap is clear, get a brightly colored fabric for the liner and the hull will have some translucency and brilliancy without paint. If your shrink wrap is blue, well, your boat will be blue.

Get the thickest gauge shrinkwrap you can find and put it on extra loose. As it shrinks it will get thicker, which is good, so apply your heat to the bottom of the boat first. That will gicve you the maximum thickness on the bottom, which is most easily damaged. When you've gotten to the point that the material is not getting any smaller, work the heat up the sides until the skin is taut. Lastly go for the sags and valleys and heat them to flatten them.

Once the skin is shrunk to fit, you may want to try running a strip of duct tape or packaging tape down the keel line on both the inside and outside to provide reinforcement against rubs from the frame and rough landings. For that matter, strips of tape on the inside where the frame rubs the skin will probably add life to the skin at a very low additional cost.

hope this helps

PGJ