Marine plywood sealing question

Hello all!

Please let me apologize in advance if this issue was brought up before and answered because I searched for it but nothing really answered my question. I have been replacing a floor on a 18ft Mariner center console and I have an issue that I'm unsure of. I have replaced the 1/2"plywood floor with 3/4" marine plywood and am going to cover it with new marine vinyl (which was originally there). My question is, do I need to seal the plywood with an epoxy or something before I glue down the vinyl or will the glue be enough on the marine plywood floor? I wasn't sure that if I sealed the plywood, the glue would adhere correctly for the vinyl. Any help is greatly appreciated!

mpm

Re: Marine plywood sealing question

yes, its recommended to put down a layer of csm and resin on the bottom before putting the floor in. then covering the floor with a coating of CSM and resin.

take a look in the restoration sections. Oops and friscoboater have some really good threads on this.

Re: Marine plywood sealing question

The origional floor was put in with no protection, IMO if you seal the wood with three good coats of spar varnish it will out last you and your children.
Glen

Re: Marine plywood sealing question

The original deck wasn't treated with anything and they last a long time so anything you do will be an improvement. Some of us are coating our wood with a couple coats of epoxy, both sides and edges. A gallon should be plenty but it will cost about $85. The Spar varnish would be much more economical but it will look so nice you'll hate to cover it.

Re: Marine plywood sealing question

Read the instructions for the glue you plan to use....the glue that was recommended for my marine carpet had in its instructions.... do not apply over varnish......

Re: Marine plywood sealing question

Wow!
Thanks for the info guys, it is appreciated. Scott- I'm not sure what CSM is (epoxy?), but I will look into it and the threads by Oops & friscoboater as well. Dozer & Michael- I'll also look into the spar varnish, might be a good way to go. STARCRAFT16SS- thanks for posting your comment, I haven't chosen what glue I'm going to use yet (just another decision!) but I will definitely look out for what they recommend in their usage instructions before I seal any plywood. Thanks again guys, you all make it a little less painful (especially on my wallet!).

Re: Marine plywood sealing question

it's marine and 3/4 so a sealing with epoxy should be fine. no csm needed. if you use polyester, then csm. epoxy is more expensive but it's not a lot of money you are talking about. personally, i would go with a few coats of epoxy like MichaelP indicated.

here's a link for epoxy...

US COMPOSITE

Re: Marine plywood sealing question

I sealed my exterior grade plywood with epoxy from here: http://www.clarkcraft.com/cgi-suppl...esin&*******=9dc4fdd1e5a2e3ba99a65448a569d333 My wood was REALLY thirsty though and sucked up 3 gallons of the stuff. Two coats each side, hitting the edges with every coat. I then went the marine vinyl route also.

http://i176.photobucket.com/albums/w200/ezmobee/New Boat/DSCF2393.jpg
http://i176.photobucket.com/albums/w200/ezmobee/New Boat/DSCF2504.jpg

Re: Marine plywood sealing question

if you thin the epoxy resin down with xylene etc, it will REALLY "wick" into the wood nicely....leaves the wood noticeably more resistant to flex after 2 coats.....and leaves the surface of wood mostly like it was before, with no glossy epoxy coating for glue to not adhere to.

Re: Marine plywood sealing question

Glass both sides.
The underside a thinner glass.

Re: Marine plywood sealing question

island mike said:

Glass both sides.
The underside a thinner glass.

Click to expand...

P.s If you just coat it with resin,The sun will first yellow it and after a while it will start to peel and flake..
resin is not strong by itself also,look into bilge paint very very strong.(1 or 2 compound)

Re: Marine plywood sealing question

Beware the lurking glassers that might try to intice you into adding fiberglass to your beautyful tinny.
Seriously---Lots of good suggestions here. You can't loose with this bunch.

Re: Marine plywood sealing question

I would not recommend any type of polyester resin, because it no purpose. Its not water proof or resistant, you could epoxy or use a water proof primer but if you do you need to check to see what you need to do to get glue to stick to it.

The suggestion of using some epoxy sealer is by far the best and suggestion. Your glue will stick to it very easily as well. You may be able to use some epoxy two part paint, but now your getting into a floor covering itself so whats the point of doing that.

Re: Marine plywood sealing question

PKomrowski said:

I would not recommend any type of polyester resin, because it no purpose. Its not water proof or resistant, you could epoxy or use a water proof primer but if you do you need to check to see what you need to do to get glue to stick to it.

The suggestion of using some epoxy sealer is by far the best and suggestion. Your glue will stick to it very easily as well. You may be able to use some epoxy two part paint, but now your getting into a floor covering itself so whats the point of doing that.

Click to expand...

I dissagree: You say neither resin is not waterproof??What do you think boats are made of??You are mistaken about glue not sticking also,If you sand the dry surface of either epoxyed wood or polyestered wood a glue WILL stick.
You are missing the point.The point is sealing his floor. plywood decks are glassed under and above with either polyester resin or epoxy.Then they are painted with a primer and then a paint.This is the most common way and one of the best to seal a deck from the elements..Resin by itself is weak and not abrasive resistent,Thats why fiberglass is added.The way I described it is the correct way to seal a deck. Regards I mike

Re: Marine plywood sealing question

No Polyester resin is absolutely not water proof. You need to do more reading on this, there are hundreds of products sold because of this problem. Any Polyester resin exposed to water will develop blisters..

They way you described will work even with polyester resin, but the primer and paint is what keeps it from absorbing water. But let me qualify that statement, it absorbs water slowly not like a sponge, but if you scratch through the paint it will slowly absorb water.

If a guy takes plywood and gives it a coat of polyester resin, lets it dry and then trowels glue onto it, the floor will allow water to set in direct contact with the polyester resin, and it will absorb water. If the floor is exposed to much water it will not last, I would estimate 5 to 10 years depending on the climate. Up North where I am the water goes in in the summer and freezes in the winter and the resin is severely compromised and more water then gets in.

If you paint it, then yes it can last a much longer time, but then why not skip the polyester resin and just paint the plywood?

By the way No boat is made of polyester resin that is in direct contact to the water, thats why we have barrier coatings, they are to keep water away from the poly. They cost a lot and are a paint to put on but are necessary because polyester resin absorbs water.

Re: Marine plywood sealing question

Having done three decks which is probably not as many as most of you, I have had zero problems reported using 2 coats of 1 part polyurethane and then covering the deck with vinyl. I had a burn mark from a soldering iron in my new JetCraft deck and I decided to replace the vinyl. When I called up to Vancover they told me 1 part poly also commonly known as Marine Spar varnish is all that's needed. I was happy to hear that I'd been using the same technique that top of the line custom boat manufacturers use. The other thing they recommend was that I not glue the vinyl down on the top side but instead cut it large enough to wrap around the edges and 3-4 inches on the opposite side. Then just use 3M-80 spray glue and stainless steel staples to secure it to the underside. My deck is in panels so that worked perfect. If you want that one piece finished look you have to glue down from the top. I've used that method also using indoor/outdoor carpet/vinyl glue applied with a 1/8" spreader/ After the vinyl is applied smooth it out with a J-roller. It works well and if you roll it out well it, you won't ever trap any water under it.

If you think about it from a "What's necesscary" vs. "Built like a Tank" the poly is fine. I used 3/4" ACX on my MonArk deck and that was "Built like a Tank". 3/4 will span 36" without sag under normal weight and there wasn't load bearing areas that were over 2'. 1/2 or 5/8 would have been fine.

Re: Marine plywood sealing question

sschefer,
What brand of polyurethane did you use? Is it a regular type or is it a special marine formulation? I was going to use the 3M -80 spray like you stated, I just wasn't sure what type of sealer to use. Can you use the 3M-80 if you glue from the top? Did you have to "rough-up" the polyurethane once it dried with a steel wool (or something similiar) or can you just spray the glue on top once the poly has dried?

Thanks again to all you guys, the feedback has been awesome!
Mpm

Re: Marine plywood sealing question

mpm87 said:

Wow!
Thanks for the info guys, it is appreciated. Scott- I'm not sure what CSM is (epoxy?), but I will look into it and the threads by Oops & friscoboater as well. Dozer & Michael- I'll also look into the spar varnish, might be a good way to go. STARCRAFT16SS- thanks for posting your comment, I haven't chosen what glue I'm going to use yet (just another decision!) but I will definitely look out for what they recommend in their usage instructions before I seal any plywood. Thanks again guys, you all make it a little less painful (especially on my wallet!).

Click to expand...

CSM = Chopped Strand Mat i think

Re: Marine plywood sealing question

PKomrowski said:

No Polyester resin is absolutely not water proof. You need to do more reading on this, there are hundreds of products sold because of this problem. Any Polyester resin exposed to water will develop blisters..

They way you described will work even with polyester resin, but the primer and paint is what keeps it from absorbing water. But let me qualify that statement, it absorbs water slowly not like a sponge, but if you scratch through the paint it will slowly absorb water.








If a guy takes plywood and gives it a coat of polyester resin, lets it dry and then trowels glue onto it, the floor will allow water to set in direct contact with the polyester resin, and it will absorb water. If the floor is exposed to much water it will not last, I would estimate 5 to 10 years depending on the climate. Up North where I am the water goes in in the summer and freezes in the winter and the resin is severely compromised and more water then gets in.

If you paint it, then yes it can last a much longer time, but then why not skip the polyester resin and just paint the plywood?

By the way No boat is made of polyester resin that is in direct contact to the water, thats why we have barrier coatings, they are to keep water away from the poly. They cost a lot and are a paint to put on but are necessary because polyester resin absorbs water.

Click to expand...

I did not read a lot about resins but i have worked with it a lot at my former job at the boatyard.This is the way we did decks.Theres nothing that can COMPLETLY seal off the wood,resins absorb water yes,But minute quantities.I know 60 year wooden boats that have no fiber issues.I never stated to leave the deck bare ,As i described in my post the process involves a primer and paint.Why not just paint as you state,Well,As I stated in my last post,A properly fibered deck will outlast the owner,You should have read my post.
Fiber both sides,Prime,Paint.Done
Regards I mike