I have called around a number of local lumber yards, to order 5' x 9' X 1/2" plywood, either douglass fir ext grade or marine grade. They make it seem that 5x9 is not made anymore, or at least not available from their suppliers.Really prefer getting the 5x9, because it will require three 4x8 to do the floor and end up with another seam. Two 5x9s will allow me to do the floor plus have a piece left to do a casting platform. Do the large chains have this to order (Home Depot or Lowes)? The ones I tried were mainly lumber yards, which I thought would be better equiped to get this.
The lumber yards did come back with some type of plywood in 5x10. Don't remember the name, but it is not one I heard of for using in boats, and it was fairly expensive. Looks like it will end up being 3 - 4x8 sheets.
Common names are Baltic birch or Russian ply. Very strong, high quality ply with high lamination count much like marine ply but I'm not sure of the glues they use for it. If it was sealed properly I think it would be great for marine use.
RodC,The name started with a "M" and sounded exotic, ie something that would come from a tropical climate. It was over $150 a sheet, and I would still need two. Three sheets of 4x8 marine cost about the same. Three sheets of ext doug fir will be less than $100. The original floor, which is out of a 60's starcraft, was only ext ply (doug fir), painted one side only, and it lasted this many years.