"Jay Pique" wrote in news:1122341807.260251.82180
@f14g2000cwb.googlegroups.com:

So my dad wants me to make a couple of replacement bumpers for his boat
trailer. Basically they are pieces of plywood covered in outdoor
carpet. He's insisting that they be made from "marine grade plywood",
in spite of my suspicion that he has no idea what "marine grade" even
means or if the originals were even made therefrom. (from it?)

"Marine grade" is one of those terms which the marketing weasels
have made essentially meaningless. About all you can be certain
about with "marine grade" is that it's made with waterproof glue
(which means it's equivalent to any exterior grade ply). Marine
_should_ mean it's made with more, thinner plys, and it has no
interior voids, but the stuff you get from Home Depot isn't made
that way. If you really want marine quality ply, you have to look
for BS1088 rated plywood.

For your boat trailer, any exterior grade ply should be fine. It's
not a structural application, you don't need the extra strength
that a true marine ply would provide. If your dad is worried about
rot, coat them with epoxy - you'd have to do that with any ply,
marine or not, to get a long life out of it.

John