afreegreek wrote:doug hodder wrote:Veneers used, glues, moisture content and a whole lot of money.....
At the risk of catching a lot of flak, I'll go out on a limb and say that for a tear, marine grade isn't necessary and I'd be willing to bet that very few do use it. I've used it as a overlay on top of my exterior grade ply sides, just because I wanted the mahogany. Living in Dayton, your humidity isn't so high that it is required for a build. Precautions should be taken to seal all the edges, whether it's marine grade or otherwise. I've used it on 4 of my tears for the sub floor and the walls, but used MDO on the last tear. Medium Density Overlay....takes on an epoxy coat great if you are doing a painted tear.
There are plenty of tears built from exterior grade that are doing just fine. I had a '49 Kit that I'm sure wasn't built from marine grade or exterior grade for all I know, and was in great shape after 40 years. It too was in a drier climate. Doug
marine grade ply is not necessary but for the few extra dollar you get a lot more than just waterproof adhesive. real marine grade is tested and certified. it has high grade core veneers and face veneers as thick as the core veneers. it's a much higher quality product all the way around whereas exterior grade is generally a lower quality product with a better glue.. the other factor is it's finish quality, hit it with 220 and your ready to go.. both faces too.
all things considered it's the best bang for the buck there is.. you get all the attributes of baltic birch with a real waterproof glue. can be had in many species, some that are half the weight of baltic birch and it comes in 4x8 and 4x10. you can also get it with the grain running across the panel if you want it.
I agree, Marine plywood is really the best choice. I have used it for kayak building with no issues. My problem is finding it. I am in Central NYS and it is impossible to find anyone that sells Okume plywood. I did find Baltic Birch, but I was told by the supplier that Baltic Birch is definately not exterior and will delaminate if exposed to any moisture. He showed me a piece of 1/8" that was damaged and discarded in their dumpster. It had rained a couple of times on it. It was warped and severely delaminated.
I still bought 4 sheets anyway, to use on the interior. I intend to seal everything with epoxy inside and out, with glass on the exterior. I am still looking for Okume ply within 150 mi.