cameldownunder

Does Marine Grade Plywood need to be treated

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Good Morning

I have to replace some part of my boat flooring. I have now cut out the same shape of new plywood, 12mm.

My question: Do I have to paint it with some timber sealant / deck oil / resin, before I glue the marine carpet on it?

Edited by cameldownunder

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Yes I would. I pay a little extra for the Stacer's to have this process when I am ordering a new boat. Marine ply being a natural product can varying in quality.

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Guest Aussie007

two coats of epoxy resin will be enough to seal the plywood, you will need to seal it if your laying down carpet because the carpet will hold moisture

thats a good deal there huey, a mate has the older stacer runabout 4.59m 2004 model and his floor went soft at the back middle

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correct me if I'm wrong , but my understanding between Marine ply & waterproof ply is the quality of the surface timber used , ie , MP provides a better finish..

The glue used on both is the same.

Unless the M.P.ply is to be used on exposed surfaces it's hard to justify the cost if being covered with carpet

Whatever you choose , give the bottom & particually the edges a good coat of paint to provide added protection

Geoff

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Guest Aussie007

correct me if I'm wrong , but my understanding between Marine ply & waterproof ply is the quality of the surface timber used , ie , MP provides a better finish..

The glue used on both is the same.

Unless the M.P.ply is to be used on exposed surfaces it's hard to justify the cost if being covered with carpet

Whatever you choose , give the bottom & particually the edges a good coat of paint to provide added protection

Geoff

your right Geoff marine ply is A/A faces meaning no imperfections and the highest quality ply, im pretty sure marine ply and the next best uses WBP (water and boil proof glue), i think there are two types of marine grade plywood australian made and imported (i could be wrong) the aussie stuff cost and absolute bomb the imported stuff is considerably cheaper but its imported

there are a few other plywoods good for boats Kokota Ply and Meranti are good and have WBP glue, im using both the Meranti and Kokoda plys on my boat build the price is a fraction of the australian marine ply

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two coats of epoxy resin will be enough to seal the plywood, you will need to seal it if your laying down carpet because the carpet will hold moisture

thats a good deal there huey, a mate has the older stacer runabout 4.59m 2004 model and his floor went soft at the back middle

I have seen all brands have soft floors from time to time-as I said being a natural product builders can get a bad patch. I doubt many, if any dealers would pay the extra at the time of the boat being made to seal the floor-but I guess when you have being doing it as long as we have you learn a trick or two.

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Marine ply will rot if it gets wet. There is a product called Evadure (International brand) which is your best bet for preventing rot.

Your will need to buy their solvent as well. Evadure is a two part epoxy, when thinned with their sovent actually penetrates the wood and fills all the microscopic voids. It is applied in multiple coats with the first diluted 50% by their solvent with subsequents coats less

diluted.

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Pay special attention to the endgrain when sealing.Any of the marine epoxies is fine,or you could use Deks Olje,an oil finish.There are a heap of different marine ply brands of widely differing qualities,none of them are waterproof,but the glue lines should be.

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I've been watching this thread as I will also need to replace some flooring soon.

Just so I've got this. Cut marine ply to size. Seal 2 coats all over. ( not just the top when it's installed?) screw down. Fit carpet?

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You can save money and get cheaper ply. You will be better off with cheaper ply such as structural

and treating it rather than just untreated marine ply. If you use Evadure it actually penetrates the

interior of the wood. If you just coat the surface with a non penetrating product water can get in

through imperfections, screw holes etc. You can over coat the Evadure wood if you wish to.

Edited by billfisher

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Good advice,my next fishing, boat will be made from structural ply,laminated in glass and epoxy.I only use marine if weight is a major consideration,but the best quality good light marine comes from Europe and is very expensive and hard to source,the last batch I bought had to be shipped from South Australia, it is for a couple of sea kayaks and a rowing scull where every kg counts.I have to say that boatbuilders are generally pretty sceptical about various manufacturers claims about how far their products penetrate more than someone else's,any good marine epoxy is a bastard to sand once it's gone off,and I guarantee you 2 decent coats will waterproof anything.Best practice is to recoat while the first still has some tack,that will give a chemical rather than just a mechanical bond.Bed any fasteners in epoxy,use a cotton bud or similar to saturate the hole,dip the screw in epoxy then instal;it will take heating with a soldering iron to get it out again once set.Epoxy needs UV protection,it begins degrading the moment it is exposed to sunlight;the carpet will take care of that.

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Why not be done with it and use laminated glass?

Just an idea.

Sent from my GT-I8730T using Tapatalk

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Guest Aussie007

u use exterior grade not structual for building plywood boats ;)

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Whoops,should have checked my post-exterior IS correct,it has the same glueline as marine,but there may be more voids and other flaws than are present in top grade marine,and lower grade faces.

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I cannot see the reply I followed, that said use only 1/4 - 1/3 of the recommended hardener. I did that, and it took the first coat about 2-3 days to cure, the second coat, with the reccommended amount of hardener took about 3 hours. I side of 1 half of the needed replacement done. It is quite a laborious work. Looks good and it looks very sealed.

Thanks for all the tips. Hope not to do this anytime soon again.

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Guest Aussie007

if your using epoxy resin it should be 5 to 1 ratio, the old resin mixture is 3 to 1, u cant use the resin on high humidity days or rainy days

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It would have been better to have used Evadure (also an epoxy but diluted with solvent) as it

penetrates the wood and makes it truely waterproof. It also densifies and strengthens the wood.

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It would have been better to have used Evadure (also an epoxy but diluted with solvent) as it

penetrates the wood and makes it truely waterproof. It also densifies and strengthens the wood.

I thought it needs to penetrate only the first layer, and the edges. The rest should be ok with the glue in between layers. I did not want to use solvent, I didnt want to "dissolve" the glue in between the layers. It is Fiberglass Resin. And the hardener is only a few mls. I really hope I didn't FK this up :-(

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It would have been better to have used Evadure (also an epoxy but diluted with solvent) as it

penetrates the wood and makes it truely waterproof. It also densifies and strengthens the wood.

Reading up on one article, it seems that using solvent is not a good idea, as the molucules of solvent are big, and leave holes. (If I did read it correctly ). Especially the "Epicraft Everdure" was not reccommended.

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Guest Aussie007

sounds like u bought Polyester resin not Epoxy resin

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sounds like u bought Polyester resin not Epoxy resin

Yes, you're correct. Is that bad? I mean, the total size is about 1800mm x 1800mm ( costs ) and I use Marine Grade Plywood, so the Coating is more of an additional protection. I'm not repairing a fiberglass hull.

Edited by cameldownunder

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Guest Aussie007

im not actually sure about polyester resin ive only played with that stuff a few times, when u sand the plywood once its coated with the polyester wear a good mask as that stuff is very bad for your health

when u mix it up from memory i only added a few drops of the hardner but i was only mixing up small batches so u may need a measuring cup to mix the right amount of catalyst

keep in mind u dont want to breath the fumes or dust when u prep the surface (sand) for gluing carpet down

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keep in mind u dont want to breath the fumes or dust when u prep the surface (sand) for gluing carpet down

That explains the headaches lately. It is not to amount of work, but the work itself.

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Polyester resin is not very waterproof compared to epoxy. The Evadure I mentioned is epoxy

but you are meant to thin it with decreasing amounts per coat of their special solvent to help

it penetrate the wood. As you mentioned there is a school of thought that solvents weaken the

epoxy and make it less waterproof compared to 'solid' epoxies. This could be true or it could

be a matter of people trying to steer you towards a rival product.

PS: I just coated some plywood with Evadure for a job i'm doing on my boat and the wood seem

to be a lot stiifer and very waterproof.

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I painted the ply floor of my first tinnie with two coats of Bondcrete nearly 30 years ago. Redid it about 5 years ago when I gave the boat to son in law, Simon. Its still in good order.

Also built my first boat (a 12Ft Hartley "Spearfish" model) using Bondcrete. A top product with wide uses.

Cheers

Paikea

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