I agree with the bending and creasing and splitting and breaking issue. I
check the bending radius of the plywood against the smallest bending
radius on the boat. I used lauan underlayment on a one sheet boat which I
bent as much as possible to get as much carrying capacity as possible, and
creased the underlayment a bit but not so that I couldn't use it. I even
soaked the panels in a rain barrel for two weeks to see if it would bend
more. I called taht boat a Loonie and sent the desgin and construction
details to Duckworks magazine where it appeared as an article. They've
archived it to CD now but I recently scanned some of the photos and put
them on my website at www.ncf.ca/~ag384/LULoonie.htm. If you look in the
index to the website www.ncf.ca/~ag384 you'll find a file called
BendingPlywood.txt which has the bending radius of some plywoods,
including what I found for lauan underlayment. However bending gunwales
and chine logs is a lot bigger problem than bending the plywood skin. I
had no trouble with the underlayment skin on the small skiff I built but
lots of trouble with the chinelogs and gunwales.

I've also posted in this newsgroup a technique I've used for finding and
filling voids in lauan underlayment. In a dark room you run a reading lamp
over the surface and look on the other side for the red streak which
indicates a void, and mark it with a pencil. Then you drill small holes
through a piece of tape and one face ply. With a caulkling gun you shoot
in some sort of goop to fill the void. I've used ordinary latex house
caulk and PL Premium polyurethane construction adhesive. Just keep
squeezing until the stuff runs out of the next hole. The piece of tape
keeps the goop from getting all over the surface of the plywood. I've
recently used the same technique to repair a crack in a small daggerboard,
drilling holes along the split, pumping in PL Premium, and weighing the
board down flat with bricks over plastic sheeting until the goop dried.
Although it sounds a bit involved there are some people who will walk a
mile to save a dime. I'm one of them. I have the dimes to prove it.

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