Sealing plywood casting deck

[Ducky]

G’day Raiders,

An age old question I know but I’m looking for advice on the best product for sealing plywood. I will be carpeting of course but need to get a good seal 1st. Seems like Everdure 2 part epoxy and Bondcrete keep coming up. Are these the best options? This is a brand new boat I’m modifying with full custom casting deck so don’t want any shortcuts and needs to last the distance, relatively speaking. Any advice would be great. Cheers!

[rickmarlin62]

I put a ply floor in my mates tinny 8yrs ago and still there with no probs..I put it in the sun and painted it with fiberglass resin...sittin in the sun the heat soaks it in and seals well...rick

[kingfishbig]

Polyester fiberglass resin is not very waterproof. You can get epoxy fiberglass resin but it is not compatible with most chopped strand. I think Evadure is the go. You can paint over it as well for extra protection and better appearance. Ship Shape marine paint is good for this. I think it is made by Norglass. 

[frankS]

I have pimped out 4-5 boats using fibreglass to seal the ply. The one I am currently doing I am using Bondall Bondgrete from (would you believe ) Bunnings, cost about 35 for 4 litres and I have found 1 ltr will do a 14' tinnie floor, so would do cast decks OK. I used it straight for one coat ( hard to brush cause its so thick ) and then thinned it with water for the 2nd coat. Appears to have sealed it every bit as good as the much more expensive fibreglsss resin. Make sure you do the edges extra well.

Shame you live so far away I could have given you a couple of ltrs as I will never use what's left from the 4 ltrs.

Frank

[Jewhunter]

Hi Frank. From my knowledge of bondcrete it's water soluble, & breaks down when wet.

[kingfishbig]

38 minutes ago, Jewhunter said:

Hi Frank. From my knowledge of bondcrete it's water soluble, & breaks down when wet.

Yes, if he is thinning it with water then that would be a hint.

[frankS]

3 hours ago, Jewhunter said:

Hi Frank. From my knowledge of bondcrete it's water soluble, & breaks down when wet.

Jewhunter. OK I have a week before I need to put the carpet over the bondcrete so what I will do is treat a sample of ply with it and place it in a tub of salt water and see what happens. If you are correct and the bondcrete starts reacting after a week I will coat it with glass resin.

Don't want the floor to fall apart do we.

I thank you for your comment and take it on board.

Frank

Edited November 11, 2017 by frankS

[frankS]

Thinking about it a bit more. Concrete, cement is also mixed with water buy when cured is waterproof, although it always has a slight water content in it, water will not penetrate it. Perhaps this stuff being a crete works the same. Anyhow I would not like to recommend a product if it fails so I will do the water test for my own curiosity .

Frank

[Jewhunter]

Hi Frank. Good idea doing the test. Render & concrete only become waterproof at a minimum of 3-1 of sand & cement mix. 4-1 or 5-1 isn't waterproof. Same with concrete. It's the cement ratio in the mix that makes it waterproof.

What you will find with a coat of bondcrete over something is that it will go a milky colour & tacky when wet. I used to use it all the time building & renovating pools. Hence why it's not used to seal natural stone or pavers around pools. A good friend of mine was a Bondall rep for many years. Hope this helps & good luck with the floor.

 

[rickmarlin62]

If fibreglass resin isnt waterproof why doesnt my boat sink...rick

[Ducky]

Thanks for the advice guys and interesting discussion, so far I think I’ll go with everdure. It’s a bit pricey but hopefully will pay for itself down the track. 

[Jewhunter]

1 hour ago, rickmarlin62 said:

If fibreglass resin isnt waterproof why doesnt my boat sink...rick

Hi Rick. It's the polyester resin that's not water waterproof & the reason fibreglass pools & boats get osmosis.

Done in layers there is polyester resin for strength & thickness, a layer of vinyl ester resin which is waterproof & then your gelcoat which is also waterproof. The vinyl ester  resin is a very important layer. It's stronger & waterproof. The gelcoat is inherently brittle & usually only 1-1.5mm thick. Any thicker & it cracks easily.

Hope that helps!

[rickmarlin62]

sorry just being sarcastic

[macca02]

I used Evadure to seal a form ply deck which was carpeted in my tinny - this was approx 8 years ago and it is literally the same as when i first did it.

The boat has been stored outside for the whole time with a cover (not a very good one mind you) over it.
Its expensive from memory and a 2 part product, though worth it!

[Ducky]

3 hours ago, macca02 said:

I used Evadure to seal a form ply deck which was carpeted in my tinny - this was approx 8 years ago and it is literally the same as when i first did it.

The boat has been stored outside for the whole time with a cover (not a very good one mind you) over it.
Its expensive from memory and a 2 part product, though worth it!

Thanks macca that’s just what I wanted to hear!

[antonywardle]

you might find some helpful tips from Ryan Moody

 

 

[biggest_kid]

Mate if you want to do it properly, get a marine grade epoxy. Do not use bondcrete, polyester fiberglass resin, PVA glue, decking oils or anything like that.

Something like WEST system epoxy or Bote Cote epoxy. Yes you will pay more for them, but that's because the manufacturers of these products actually put research into them and they work. These premium marine epoxies are better because they have a low solvent but high solids content.
Apparently when the solvent used to thin-out (make them runnier) cheaper epoxies evaporates it leaves microscopic pores or 'tunnel's through the finish, allowing minuscule amounts of water in. It might not be much water, but over time it does damage to the wood. It should be noted that water and acetone are common solvents used to thin epoxy, both of which will degas in this way.

I recently used Bote Cote to seal a piece of 7mm ply to secure some switch panels to. And my God is it good stuff, I can safely say there won't be any water getting into that wood for a long, long time. Here is how to use it:

1) First cut all pieces to size and dry fit them in place with screws. Do this first because you need to seal all cut edges and holes drilled through the wood well as exposed edges are most susceptible to water ingress.
2) Remove the pieces of wood from the boat and sand properly
3) Use TPRDA, a low solvent thinner + timber preservative in one made from the same company that makes the Bote Cote, to thin the epoxy for the first coat
4) Apply this first thinned coat to the edges of the pieces and all screw holes, making sure it soaks right in - which it should have no trouble doing as plywood is exceptionally porous. After doing the edges coat the faces of each piece as well.
5) Wait for the first coat to cure and sand it lightly
6) Apply a 2nd coat of unthinned Bote Cote
7) A 3rd coat can be applied if you want to be thorough, but according to the manufacturer is not necessary unless the wood will be submerged under the waterline (this stuff was originally manufactured for wooden boat builders to seal their wood, so that should be a testament to how good it is)

Now just so you know I do not work for the company who makes this stuff or get paid to endorse it. It's just that I used it recently and think it is an exceptional product and thought I would share to help out fellow boaties.

Like I said I recently did a switch panel with it, and was using that as a trial. Well it passed the trial with flying colours and I will now be doing my tinny floor with it too. A wise man once said ''do it right or do it twice.'' I'm not saying the cheaper epoxies wont work, they just won't last as long. If you cannot afford the more expensive stuff then by all means use the cheaper brands, but please do not use bondcrete or any of those other products I mentioned.

Anyway hopefully this helps someone who was in the same boat as me a while back (excuse the pun).

[Ducky]

9 hours ago, biggest_kid said:

Mate if you want to do it properly, get a marine grade epoxy. Do not use bondcrete, polyester fiberglass resin, PVA glue, decking oils or anything like that.

Something like WEST system epoxy or Bote Cote epoxy. Yes you will pay more for them, but that's because the manufacturers of these products actually put research into them and they work. These premium marine epoxies are better because they have a low solvent but high solids content.
Apparently when the solvent used to thin-out (make them runnier) cheaper epoxies evaporates it leaves microscopic pores or 'tunnel's through the finish, allowing minuscule amounts of water in. It might not be much water, but over time it does damage to the wood. It should be noted that water and acetone are common solvents used to thin epoxy, both of which will degas in this way.

I recently used Bote Cote to seal a piece of 7mm ply to secure some switch panels to. And my God is it good stuff, I can safely say there won't be any water getting into that wood for a long, long time. Here is how to use it:

1) First cut all pieces to size and dry fit them in place with screws. Do this first because you need to seal all cut edges and holes drilled through the wood well as exposed edges are most susceptible to water ingress.
2) Remove the pieces of wood from the boat and sand properly
3) Use TPRDA, a low solvent thinner + timber preservative in one made from the same company that makes the Bote Cote, to thin the epoxy for the first coat
4) Apply this first thinned coat to the edges of the pieces and all screw holes, making sure it soaks right in - which it should have no trouble doing as plywood is exceptionally porous. After doing the edges coat the faces of each piece as well.
5) Wait for the first coat to cure and sand it lightly
6) Apply a 2nd coat of unthinned Bote Cote
7) A 3rd coat can be applied if you want to be thorough, but according to the manufacturer is not necessary unless the wood will be submerged under the waterline (this stuff was originally manufactured for wooden boat builders to seal their wood, so that should be a testament to how good it is)

Now just so you know I do not work for the company who makes this stuff or get paid to endorse it. It's just that I used it recently and think it is an exceptional product and thought I would share to help out fellow boaties.

Like I said I recently did a switch panel with it, and was using that as a trial. Well it passed the trial with flying colours and I will now be doing my tinny floor with it too. A wise man once said ''do it right or do it twice.'' I'm not saying the cheaper epoxies wont work, they just won't last as long. If you cannot afford the more expensive stuff then by all means use the cheaper brands, but please do not use bondcrete or any of those other products I mentioned.

Anyway hopefully this helps someone who was in the same boat as me a while back (excuse the pun).

That’s brilliant mate, some detailed 1st hand experience. I’m not afraid to fork out for the right product. A quick look online it seems to tick the boxes. Cheers!