*THE HULL TRUTH is the world's largest FREE network for the discussion of Boating & Fishing. Whether you're researching a new boat, or are a seasoned Captain, you'll find The Hull Truth Boating & Fishing Message Forum contains a wealth of information from Boaters and Sportfishermen around the world.
Welcome to the updated THT!
If you are having trouble signing in, please email feedback@thehulltruth.com with your username and we will help you. We thank you for your patience as we help you access the new site!
Someone just told me that all plywood made today is what used to be called marine (waterproof glue). I don't have real confirmation but it may be worth asking your lumber yard guy.
It's not (only) the glue that makes it marine grade. It's the lack of voids in the laminates. Look at the edge of a piece of regular plywood and then look at the edge of a piece of marine grade.
To the OP: Have you looked in the phone book and called around to any lumberyards?
Our Home Depot caries it. I don't know if their price is competitive or not because I've never shopped around for it. I also don't know if it is available in different grades as interior or furniture grade plywoods are but the stuff I've seen looked like it would be plenty good for a pontoon deck.
__________________
*Sometimes I sound like I know more than I do. Other times I don't.
Home Depot does not list marine plywood on their web site. I have never seen Marine plywood in our local (Pensacola) Home Depot stores. There is quite a difference between marine plywood and A/B exteriior. As Booker said, there are no voids in the inner layers. A/B exterior has voids in the inner layers. Some Marine plywoods are higher quality than others: Okoume, Hydrotek, Aquatek are all excellent brands of Marine Ply. These tend to have tigher laminations and more laminates than some of the cheaper woods. The hardwood plywoods are generally better than softwood plywoods. Soft plywoods tend to check--and then rot.
Can you use pressure treated wood? It has been used for transoms and stringers, but probably not a good choice for decks. It tends to warp. In either case, if you use plywood, be sure and epoxy saturate it, glass the bottom and top, with at least one layer of 6 oz glass, I prefer 12oz biaxial. If possiable glass the edges also. If you have to joint the plywood, scarf the joint 12: 1 and use epoxy glue, then glass over.
There is also the possibility of using a synthetic. I just re-did a cockpit with Nidacore, a hex cell, material which has mat on both sides and laminates well. It is not as strong as plywood, and I don't think I would use it for the torque forces which might occur in the deck of a pontoon boat--unless you used substantial glass, and were sure to use epoxy/glass re=inforcements where the hulls attatch.
Don't use the cheap woods, it is only a few more bucks, but it will make all of the difference--and avoid Home depot for this type of wood. Most marine wood suppliers will drop ship to boat yards or some place near your home. If I need any specialized wood not locally available, it is sent to a friends shipwright's shop from New Orleans area.
NO! Common mistake when you deal with people in the building trades. Were not dealing in the building trades, were in the boat building end.
All exterior plywood uses the same glue. It is waterproof. Interior plywood [Oak, Birch, etc,etc has a diffreent glue and will delaminate when exposed to water.
Now on to weight. The "Most" common Marine Plywood is Fir. [There are others.] Fir is lighter weight [good for boats] than Pine plywood that you find in the building trades.
Then there is the spec on the void factor.
Try the Freeze / Boil test on any plywood you are thinking of using. With a small piece, Boil it for 5min then Freeze it for 2hrs, Then boil it again for 5min, then freeze it again for 2hrs, then boil it again for 5min.
A/B Fir marine will pass this test and not delaminate. Others will not.
Quote:
I have never seen Marine plywood in our local (Pensacola) Home Depot stores.
Both Lowes and home Depot had it at one time Bob. The price was right, BUT it was all beat to crap. They couldn't sell it ans thus discontinued it. This was 6 or 7yrs ago.
Been told never to fiberglass over treated wood. But I did it anyway and was successful or at least it seemed to hold up 8 years no rot no delamination.
I roofed a shrimp boat with treated 3/4" plywood, let it bleach out for about 30 hot summer days, I cut some resin with styrene and laid on a good wetting coat, it soaked in pretty good. After that I laid 4 layers of 1/4 oz mat (2 at a time). After 8 years I had no issues, no leaks, warps etc... The rationale behind NOT using pressure treated was that the liquid inside the wood, would disallow absorption of resin and resin would not stick. Mine stuck fine.
__________________ Generally inadvisable to eject over an area you have just bombed.
I use a product called Advantek for all my subfloors. Now, I am not endorsing it's use in marine applications but I will say that I have personally seen it exposed to WX for MONTHS at a time with absolutely no delaminating/swelling. It's HEAVY and very strong.
Building "stuff". Building a house, who cares how heavy it is?
Building a heavy boat, you pay more in the beginning for extra materials and keep paying more in fuel costs to push it.
Dude thats some good info your spewin, I talked my brother out of treated plywood and he had already bought and cutout all new flooring for his 27' Magnum. The boat is already a slug( late 80's) he got some real marine plywood and sealed it up good. I like your rig, did you paint the truck to match boat?
I would order it from here. http://plywood.boatbuildercentral.com/ My son and I built a 12 foot wood skiff last year and got our wood from this place. Good prices, excellent choices, good shipping.
3/4 " marine plywood 
It's Awlgrip too. 
