Joe,
Both of these materials have drawbacks but they will work. Door-skins are about 1/8 in thick so they're not very sturdy. They're decorative interior panels and are not made with waterproof glue. If water gets to a door-skin it could delaminate. If this stuff was used on a S&G it would require 6 oz. 'glass sheathing on both sides. Since you have a frame doing the outside will probably be sufficient.
Luan will work also. Luan is not a structural product. It's a 1/4 in. thick shim that's laid over rough flooring so that vinyl sheet flooring or tile can be laid on top. The outer plys are very thin and don't contribute much strength to the product. It needs sheathing also.
If this were my call I'd use the door-skins because they're lighter and would be a suitable base for the 'glass/epoxy which will be the real strength of the hull. The inside of the boat needs at least two coats of epoxy to insure that water never gets to the door-skins.
Whichever way you go let us know how it turns out.
Charlie

: Hello,

: I am building a kayak from Hartley Marine http://www.hartley-boats.com/
: That is a 16' foot double. I started building it before I knew about
: stitch and glue, or I would have saved myself a lot of work. But, I now
: have the framework built and am about to sheathe it in. On the advice of a
: local boatbuilder I decided to use what I believe are called, 'door
: panels' or something similar. A very thin kind of plywood. The boatbuilder
: in question said that since I had a relatively cheap source of epoxy, luan
: would be a good choice. i could coat it well, he said, then cover it with
: fiberglass. I just want to check this out with you. Is this a good idea? I
: cut the luan in strips and plank the boat, rather than the stitch and glew
: method. What do you think.

: Although probably an older design, and with a frame, this boat seems to me
: similar to the CLC Mill Creek 16. I am wondering if it is similar enough
: to put their sailing rig on it. I'd appreciate any help,
: Joe