doug hodder wrote:I agree....while I'm certainly no production boat or tear builder I've built several of both. Home/ shade tree builders aren't supporting the bulk of the marine grade ply industry. However, having also worked in the sign industry for a number of years....my option would be to go with the MDO ply on a non aluminum clad tear, unless it's a woodie. Marine grade ply isn't necessary on a tear, but on the boats I've build, I do use it on the hull. Done both fir and mahogany. I believe that the 1088 BS certified ply does have an anti-fungicidal thing in the glues. Not sure if the regular exterior does.
What marine grade ply does have is a thicker exterior veneer and in the mahoganies as opposed to many of the other veneered plys, gives you a chance to not sand through it, unless you get carried away. Doesn't really matter if it's going to be covered with aluminum or painted, but on a woodie to be finished "bright"...that's what I've done. I get the thin stuff, and laminate it to a regular ply substrate...it's just for the grain and color. FWIW. Doug
1088 does and doesn't have fungicides in the glue.. it's an option but not a requirement for the certification.. you can also get pressure treated 1088 both still wet, and dried post treatment.
marine ply and most exterior grade ply have thick face veneers because they are primarily structural.. most interior and cabinet grades have thin face veneers because they are sanded and intended for paint or veneer applications either in the factory or post production.. they use the outer layers to 'smoothen" the surface of what are generally thick and very coarse inner veneers.. the exception to his is very high grade ply like Appleply and Baltic Birch where all veneers are A or B grade including the core.. they also have relatively thick face veneer and a larger number of core veneers..
these are all generalizations because there is literally hundreds of variations on the market and some specifications overlap into other categories.. for example, we have sheets of 7ply 7/16" poplar.. it's 1088 with A grade core and faces of equal thickness and has the face veneers running across the 4 ft length.. not something you find at Home Depot