I built a kayak with the Russian Birch 8 years ago and it is still going great. It is a little heavy. If you look at the thickness of each layer it is clear that it is not a structural plywood. The thickness varies significantly and ounce for ounce I don't think it compares at all with marine wood but it has worked fine for me. The skin is thin so you need to be careful sanding on the edges.
Scott

: Jay:

: When I did my initial testing on the Russian Birch, I threw in a
: piece of, what I assumed, was exterior grade fir plywood. After
: one hour boiling in the pot, the plies basically fell apart in
: my hands. Perhpas the plies just soaked up to much water, I
: don't know.

: I cut all my frames from the Russian Birch and never came across a
: single void. The wood has swelled slighly after the testing and
: other than a graying in colur, retains inital shape and
: hardness. When I bought the sheet, it was not bowed or warped,
: as you often find with cheaper plywood. It cut extremly clean
: with very little splintering. It was finished both sides without
: even the smallest of knots. The thin, 13 plies I guess add to
: the stability. I'm guessing this is cabinet grade plywood.

: Although I live in a very "marine" location where
: commercial fishing is still big part of the economy and offshore
: oils is booming like you wouldn't believe, there is no marine
: plywood to be had locally. For me to order a 1/2" full
: sheet of Okoume, it would cost me 169.99 for the sheet and 98.00
: to ship it + tax. Finding out that a 30.00, 2x4 sheet of Russian
: Birch will fit the bill, is just gravy!!

: Cheers,

: Sean