Marine ply floor

[peeterb]

do you need to coat both side of the marine plywood deck with resin.I have read that you only cover the top side .<br /><br />Thanks for any advice.

 

[Boomyal]

Re: Marine ply floor

Absolutely essential to coat the under side of the ply. That's where they rot from. It's best to use a penetrating resin (CPES) first, letting the ends drink as much as they will. If using standard epoxy, thin as much as the mfg allows. If properly coated, I don't think it's necessary to go to the expense of marine ply. The only difference between ABX and marine is the total lack of voids and a whole bunch of dollars. <br /><br />I was able to buy some 1/2" ABX, 7 ply, mahogany one side for $25.00 a sheet. It does have small void which I pumped full of resin where visible on the ends.

 

[rverano]

Re: Marine ply floor

Not totally true on the marine plywood. My friend is a cabinet builder and said the difference is in the glue that bonds the laminates together on marine grade plywood. He said that regular plywood does not use the same type of glue. That's how you can easily tell if old plywood is not marine grade because of how the laminates seperate.

 

[Boomyal]

Re: Marine ply floor

Originally posted by rverano:<br /> Not totally true on the marine plywood. My friend is a cabinet builder and said the difference is in the glue that bonds the laminates together on marine grade plywood. He said that regular plywood does not use the same type of glue. That's how you can easily tell if old plywood is not marine grade because of how the laminates seperate.

All indicators, discussed in this forum, point to exterior grades and marine grades using the same waterproof glue. The only difference is the lack of voids in marine ply. That all, I recall, comes from at least one of our esteemed members, who is in the plywood business. You can do a 'search' for marine plywood and see all the past information.

 

[petrolhead]

Re: Marine ply floor

Rverano, I'm afraid your friend is wrong, both Marine and Exterior ply use the same Phenolic Formaldehyde adhesive, both are rated WBP (Water and Boil Proof). The difference is in the allowable species used for marine ply and the lack of voids.<br />You did say your friend said "regular" ply, maybe he meant regular ply for indoor use? In which case he would be correct, but Boomyal was comparing marine and ABX (ABX being an exterior grade, X for Exterior).

 

[lark2004]

Re: Marine ply floor

And the answer is still YES, you need to coat both sides of the floor. This prevents any moisture under the floor soaking into the ply.

 

[Elk Chaser]

Re: Marine ply floor

Yes, all of this is true......<br /><br />But, using exterior grade ply will not prevent moisture from condensing in the voids in the middle of the wood where you cannot pump it full of resin and the result is eventually the wood will rot from the inside out. <br /><br />No way to stop this from happening.

 

[starrider_68]

Re: Marine ply floor

Ok ... here is a stupid question. In looking at building my project boat I am left to wonder... why do I need to use plywood at all? cant I use O.S.B. (oriented strand board) ** not particle board** for the forming of the shell and use "glass" or "reisen" to cover it...If done correctly the osb should give as much life as plywood...shouldnt it?

 

[TwoBallScrewBall]

Re: Marine ply floor

OSB is 20% heavier than plywood, ,which results in at least a 20% heavier boat, and is similar in strength but not the same, it is not as strong as ply. Also, not sure if you can get X grade OSB.

 

[petrolhead]

Re: Marine ply floor

OSB won't last, guarantee it.

 

[BillP]

Re: Marine ply floor

Ditto...you need to coat the underside of the floor to prevent rot or getting waterlogged. I used pressure treated ply to get away from the rot problem. Once throughly dry, the cca pt process won't stop resin from sticking. It's also available in marine grade if you want to spend the bucks.

 

[thehermit]

Re: Marine ply floor

glass...use a plastic spreader...be effecient..and it dosnt really take a whole lot extra to do the underneath of deck.good luck

 

[Boomyal]

Re: Marine ply floor

Home Cheepo, and I assume other places, have standard 9" paint roller specifically for epoxy. About $2.93 each. I bought several and cut them to fit my 4" trim roller. I just pour some resin out onto the flat surface and roll away. They put on a real nice smooth, even layer of resin and do not shed or soak up a bunch of resin. As soon as you're done, remove the roller and wipe off your tool. They do real well for coating all your dimensional lumber too.<br /><br />I even used the rollers to wet out all the glass tape I used on the stringers. It works especially good for applying resin on vertical surfaces that you will apply glass to.