marine ply query

It's worth splashing out on the real thing. WPB is all right for quick, temporary repairs or internal structural work clear of the bilges. The real benefit of MArine Ply is the lack of voids. In WBP internal laminate sections might not properly meet up leaving internal voids where damp can reside and start to spread all sorts of nasty side effects. You'll eventually see wrinkling on badly affected panels. Sometimes you can be lucky with WPB but it's best not to take a chance and go for the real thing. I went to Waller & Wickham for plywood when building little sailboats for the kids and repairing old boats. They used to be very good.

Even better - use epoxy resin.

Yes, the cut edges are plywood's Achilles heel. I remember the late Peter Dunne of Rogerstown showing me how to make what he called "bones" to dress the exposed edges of marine ply by rebating the ply into hardwood slips, or stringers, as the case might be.

I have to say Feargal, that your boatbuilding work is first class.