: I tried to use the 1/4 inch luan for the deck of the Mill Creek, but it
: couldn't make the radius of the curve.

My experience is similar to Dan's. Five or 6mm luan is mainly core with veneer skins. Its been years since I've seen any luan with voids. Recently, it is showing up with worm holes on one face verneer. Glassed it is strong enough for any kayak. But its ability to assume the tight radii of a curved deck is limited. Three mm doorskins will work much better. I found I had to go about 3 hours down the interstate to get doorskins. It seems that the flooring trade, which mostly uses this product, demands it in some areas and doesn't in others.

You can cheat a little by back scoring 5 or 6mm luan to make it more flexible. Do this by running a guided router with a 1/8" veining bit set about 1/8" deep down the length of your sheets. I'd score the sheet every inch. I know a sheet scored in this manner will assume the curves of the Mill Creek 13' deck. Be advised that the outer veneer may crack over the scoring if the sheet isn't formed evenly into shape. To restore some of the strength lost by scoring thickened epoxy should be squeegee'd into the scores just before the deck is fastened down.

Another option is 5-6mm for the hull and strips for the deck.