Well, thanks for the replies. Now, I know more about plywood than I ever could have imagined. I have brought this boat up on this forum earlier and don't want to overstay my welcome on this. But, it is kind of slow going for me. But, if your patience is still holding, I will respond to some of the points you raised:

First, my boat is not a S&G. It has a couple of frames, a centerplank and stringers. I attatch the plywood to this with nails. ( I believe someone looked up my model when I first posted, it is a 16' double, designed by Hartley Marine and sold on the Glen L website). I suppose this means that the plywood does not have to bend so much.

Secondly, someone asked where I live. It is Montréal. I fear that shipping costs would be prohibitive.

Thirdly, I am hoping to keep the finish natural and cover it with fiberglass.

Fourthly, thickness. Someone mentionned that one eigth might be too thin. I believe someone said that that maybe too thin. that may solve the problem. Because I believe one place said that they had 4mm and 6mm sizes in 1088 BS but not one eigth.

Fifthly, I am changing as I go along. First, I had planned to use luan. I bought it, in fact. But, after considering the time I am putting in and the nice wood that I have for the frame, I decided that I should invest a little more in the plywood.

As I am very inexperienced at this, I am open to any suggestions you might make. Thanks for all the help so far!
Joe

: Hey Joe

: Getting the okoueme: Where do you live? Hardwood shops are the usual place to
: go for such things, the Home Depots of the world don't carry that stuff.
: There's a listing out

: What it is: There's real okoume plywood that meets the British Standard (BS)
: 1088 and there are lots of fakes. (All the fakes are out of the China,
: Malayasia, Indonesia area, the same place where crappy tools and goods are
: made, and the majority of spam houses are, too.)
: This link has the BS 1088 standard:
: http://www.glen-l.com/wood-plywood/okoume.html
: There's a real good article in this month's Wooden Boat magazine by Chris
: Kulzinski, the guy who wrote the book on building S & G kayaks, all
: about okoume plywood. It's a must-read!

: Some additional information on working with marine plys, including okoume is
: found here: http://www.glen-l.com/wood-plywood/wp-index.html#index

: Where to get it: This link has a list, somewhat dated, that can help find it.
: Buying and transporting sheets is better then ordering and shipping. You
: want to inspect the sheeys for cracks, voids, gouges, bogus stamps, etc.
: The lists: http://www.glen-l.com/resources/lumber-suppliers.html
: http://www.woodfinder.com/

: Things to keep in mind: That BS1088 certification is hard to acheive, few
: manufacturers are certified in the world, and even fewer are certified by
: Lloyd's of London. That said, there are lots of plys that have these
: stickers stuck on that say that they meet the BS 1088 standard. The only
: "commonly" available BS1088 standard okoume ply certified by
: Lloyd's is from the Joubert group in France (Spain, UK and elsewhere).
: They have a staff at the manufacturing plants near where the okoume grows
: that watch the process daily. The other groups haven't responded to my
: queries or if they do, have a QA/QC program that is insufficient. The
: Joubert link is: http://www.joubert-group.com/uk/1.htm

: On thickness: To quote Jethro Tull, "To be thick, as a brick" The
: standard for kayaks seems to be between 1/4 inch (which "equals"
: 6 mm ply) and 4 mm (which "equals" 3/16 ply). The difference is
: that the thicker stuff has 5 ply and the thinner stuff has 3 ply. There's
: a 20% difference in weight with the thicker ply being about 20 pounds per
: 4X8 sheet and the thinner 4 mm being 16 pounds per 4 X 8 sheet.
: The 1/8 inch is used by some but to me seems too thin. There are lots on this
: board who have made wonder yaks with the thin stuff, but wimps like I
: don't dare to go thinner then 4 mm. Then again, I'm new to this S & G
: thing and of course dove in with helping on several yaks in the 'hood. The
: 6 mm seems too heavy but easy to work with, the 4 mm is just fun and
: light. A friend and I are building his S & G Night Heron in hopefully
: 10 days, and are using ply we found locally, cutting it out, etc.

: Hope this helps