TOPIC: plywwod selection for the floor

The floor on the Glastron is 1/2", probably a regular exterior grade plywood. What would be a good choice for a replacement? The same stuff? A hardwood plywood (birch, oak, etc.)? I really don't think I need marine plywood since it is not a major structural part of the hull. Am I wrong on this? Personally, I'm leaning towards a hardwood, but would a regular plywood epoxy coated be satisfactory?

Hey bud. I wouldn't go too terribly far from either marine grade or if you have to exterior grade plywood. The wood species is less of an issue than the glue or adhesive that holds it all together. We'd look pretty stupid if we got all that work done just to have delamination down the road. Good luck.

Shipster is 100% correct. Many a time I thought I would save a little money not buying marine grade and ended up costing me alot more. Also, the space between the hull and upper floor will gain moisture and rot the ply from the inside out, unless you foam the inside space, which I would suggest. Also, you need marine grade glue(resin) when installing the floor. If you're not going to foam, then you want to prefinish the underside first before installing.

I've been told that exterior grade plywood is now made with waterproof glue, that's what I used on my floor (1/2"). I did soak with thinned resin and then fiberglass (csm) both sides before the installation, with an additional layer of csm over it once it was "glued and screwed" down. 1708 Biax strips along the seams and sides, for added strength. Lord knows I'm no expert, just doing the best I can with what I have to work with.

to ALL,

MDO plywood will likely outlast the hull if coated with penetrating epoxy & ALSO likely to outlast the hull if NOT coated with epoxy, as it lasts for DECADES as "the big green highway signs" when simply painted.

these days (personally) i see NO good reason to use marine ply for ANY job unless the panels must be BENT a great deal.
("Dynamite" Payson & his son built a 18' CLAM SKIFF out of 3-ply pine exterior grade plywood over 18 years ago & it has remained FINE in commercial fishing/clamming/lobstering all that time with ONLY painting with latex house paint.)

yours, satx

"Marine grade" is really overkill unless, as SATX mentions, you are going to be doing some extreme bending... the only real difference is the allowable number of voids in the inner laminate. If you can find a good quality exterior grade ply, it will be fine. It can be tough to find, though- Most of the stuff sold at the 'big box' HE stores is pretty bad.

Lowes used to stock a nice plywood made by a company called Arauco. It was exterior grade, AC, and there were very few, if any, voids... I used it in all my projects, and had come to really like it. Regrettably, the factory burnt down last year, and you can't get it any more. They are in the process of rebuilding the factory, so hopefully it will be available again soon!

-Andrew

I wanted marine grade for the transom because of the loading. No voids seems like a good idea. We a couple of local lumber yards that have higher quality wood, but I have never checked them for plywood. The place where I got the marine stuff is only about 12 miles away so I could always go there, but they tend to be very expensive.

I am looking at a similar problem. Does this look like an original floor, or a repair? I was just going to patch it, but worry that I may be trapping moisture under the patch. I don't see any drains or access under the floor.

Daniel77 et. all.,

IF i was doing that job, i would cut some holes in the floor & put grates over the holes so that NO water could get trapped under there AND gasoling vapor (which PUDDLES like water) couldn't gtet rapped either.
(most marine catalogues have grates in various sizes/materials & they are NOT expensive.)

yours, satx

Daniel, I would replace the whole thing. You have no idea the true extent of the damage just by that one area.

Satx, the only problem I see with the grate idea is that it would also potentially allow more water and gasoline fumes under the floor as well as make it easier (at least for the water) to remove them. Getting fumes from under a floor would likely require some kind of blower.

There was also some mention about filling the space with foam and seal it up. I am very reluctant to go that route as foam can get soaked if there is any leak.

thetudor,

in my experience neither actually happens though a "bilge blower" is a GOOD plan.

yours, satx