what is the difference between marine grade plywood, and regular everyday plywood? and how does this translate into differences for boat building? just figured that if it was all sealed in epoxy, it might not matter.
just curious.
brad
Marine plywood vs. Regular
I'm not an expert in this, but I think there are two main differences. First, the marine grade plywood that I know of is made of a different wood than what we typically find as plywood which is spruce and fir. Secondly, and most importantly, marine grade plywood is has no voids (or almost no voids?) whereas typical plywood will. If you have a sheet of regular plywood and if its thin enough, if you hold it up to some light you will see a bunch of areas that let more light through because it is missing material in the middle.
Plywood
Camper1, I built a stitch & glue kayak with luana plywood (1/4 underlayment) the kayak turned out ok as far as functionality, but there two things I found different from the kit I bought with 3mm marine plywood. One would be the weight it is 2 times heavier than marine plywood. Appox. 6mm to 3mm thick for marine plywood. The veneer on underlayment is very thin and of poor quality. I ended up painting the kayak because of sanding thru the veneer. After a year of use, and being stored outside the kayak is standing up well with no problems of delaminating, or any other noticeable concerns. If the above problems do not concern you this may be a good alternative.
keith
keith
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Dark Horse
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- Joined: Thu Dec 30, 2004 8:36 pm
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Most Marine Plywood is either Meranti or Oklume, both are variants of Mahogany. Meranti is more resistant to rot, Oklume is lighter. Most suggest looking for the Lloyds stamp to verify grade and that it truly is Marine ply.
The glues resist water penetration in to the glue joint. A backyard experiment is to take a small piece say 6"x1' and boil it for a bit Marine Ply will not delaminate, most exterior plywood is soup.
Exterior grade Fir ply has been used to some success building boats, but it must be 100% epoxy encapsulated and a layer of Fiberglass is highly recommended to slow the Checking that Fir will have. It will not stop the checking only slow it down and keep the checks smaller. For a work boat no big deal, for a pride and joy its heart wrenching. Either way it uses more epoxy than the Mahogany Marine Ply, and ends up costing more as well, due to the extra Epoxy and Glass. Not to mention all the extra weight that ends up being added.
Jim
The glues resist water penetration in to the glue joint. A backyard experiment is to take a small piece say 6"x1' and boil it for a bit Marine Ply will not delaminate, most exterior plywood is soup.
Exterior grade Fir ply has been used to some success building boats, but it must be 100% epoxy encapsulated and a layer of Fiberglass is highly recommended to slow the Checking that Fir will have. It will not stop the checking only slow it down and keep the checks smaller. For a work boat no big deal, for a pride and joy its heart wrenching. Either way it uses more epoxy than the Mahogany Marine Ply, and ends up costing more as well, due to the extra Epoxy and Glass. Not to mention all the extra weight that ends up being added.
Jim