If Baltic birch is the same as Scandinavian birch then I can tell you something about it. In Scandinavia Birch is an all-purpose hardwood used in furniture skis, all kind of tools, floors. I think it is a bit to heavy to use as boat plywood. And also birch can't take water any good. So you have to protect it with epoxy. But I have used 1.5mm birch airplane plywood as a canoe deck with very good result. I have seen birch plywood kayaks and well keept they looks nice

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