How to coat plywood with 2-part epoxy resin

Stemar said:
Whatever coating you put on will be damaged the first time you drag the dinghy across it and will be penetrated after a few times at best. Water will then get in and be prevented from evaporating by the coating. I wonder if the best thing wouldn't be a couple of battens underneath to keep it off the wet ground and leaving the wood untreated.
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Or get an old pallet etc.
 
A mate who's a whizz with composites says it's a good idea to mix a very small quantity of collodial sillica in the coating mix. Apparently the hardner can leach into the wood faster than the resin, thus ending up with an imperfect cure. The collodial sillica stops this hapening.
 
Stemar said:
Whatever coating you put on will be damaged the first time you drag the dinghy across it and will be penetrated after a few times at best. Water will then get in and be prevented from evaporating by the coating. I wonder if the best thing wouldn't be a couple of battens underneath to keep it off the wet ground and leaving the wood untreated.
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Yes, or thin the resin after mixing to get good penetration into the wood.
michael_w said:
A mate who's a whizz with composites says it's a good idea to mix a very small quantity of collodial sillica in the coating mix. Apparently the hardner can leach into the wood faster than the resin, thus ending up with an imperfect cure. The collodial sillica stops this hapening.
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Yes, or thin the resin after mixing to get good penetration into the wood, then recoat with unthinned which should then stay on the surface.

Boo2
 
Sorry forgot to add the dingy storage area is made of a steel grid! So any water just falls below the grid, very very strong, don't rust, the problem is where my dingy is stored they have to be put away side on, it's bloody awkward trying to lift a 9ft dingy on you own, bit by bit across the metal grid, anything at all catches in the grid, ie my mounted plastic wheel mounts. So hense the use of ply, my question wasn't answered, is the resin better than the Yacht varnish, WBP ply is only one step down from Marine ply. This off cut only cost me £4. Full sht is £28.
 
Binman said:
Sorry forgot to add the dingy storage area is made of a steel grid! So any water just falls below the grid, very very strong, don't rust, the problem is where my dingy is stored they have to be put away side on, it's bloody awkward trying to lift a 9ft dingy on you own, bit by bit across the metal grid, anything at all catches in the grid, ie my mounted plastic wheel mounts. So hense the use of ply, my question wasn't answered, is the resin better than the Yacht varnish, WBP ply is only one step down from Marine ply. This off cut only cost me £4. Full sht is £28.
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If it's in full daylight then you will need to coat the epoxy with a UV barrier like outdoor varnish or paint anyway. IMHO thinned epoxy will give the longest lasting rot-proofness / water-proofness but as I say you may need to apply a top coat of something else too. If you want to apply just one finish then yacht or floor varnish should be OK but won't last as long.

Boo2
 
Cripes. In spite of reading plenty about epoxy, and having been very satisfied with the appearance of my epoxied ply, it hadn't occurred to me yet to cover the epoxy as well. Thanks!

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Old question, then...what's the best, longest-lasting varnish for cockpit-woodwork? Colour isn't much of a concern, I only want that protective layer.
 
Binman said:
Sorry forgot to add the dingy storage area is made of a steel grid! So any water just falls below the grid, very very strong, don't rust, the problem is where my dingy is stored they have to be put away side on, it's bloody awkward trying to lift a 9ft dingy on you own, bit by bit across the metal grid, anything at all catches in the grid, ie my mounted plastic wheel mounts. So hense the use of ply, my question wasn't answered, is the resin better than the Yacht varnish, WBP ply is only one step down from Marine ply. This off cut only cost me £4. Full sht is £28.
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How about using cheap teak oil, (decking oil?) on it?

WBP ply AFAIK means the glue is a certain standard, it says very little about the wood.
I've used cheap WBP for bits of my tender and it's lasted well, other wbp ply has lasted badly. pot luck?
A proper enough coating of epoxy to be worthwhile will probably cost more than the plywood.
And UV will destroy it in a few years anyway.

I'd say just paint it, but that will mark the boat when dragged over it.

Ps, it's not the £4 you paid, it's the £28 to replace???
 
A year ago (possibly two, or even three) I had a nice little idea of putting flat ply floors in the Osprey to keep SWMBO's backside dry...

...and some time early last summer I put two good coats of West epoxy on some of the sections of ply I had cut to size. Then I forgot about it and went sailing, and the panels stayed for six months in the garage. Lately I finally got round to cutting the stern cockpit floor panels to size, and the other day I gave them each a coat on one side...

...today I went back and took a look, and was shocked to find that it looks as if I'd done it whilst asleep (I wasn't).

There are some thickly-covered areas, but also large expanses of apparently bare wood. I don't understand it. I was wide awake and sober, and in no hurry, having wiped the wood clean with acetone. Might it relate to the low temperatures in recent weeks?

And today, looking at the forward boards which I gave two coats each in July last year, I found the finish gives the strong impression of having been subjected to long months of sunlight and abrasion, despite their having been stored in a windowless garage.

I wonder what I'm doing wrong? Could it be because I paint the stuff on with the ply upright like a wall? Maybe the finish would be more consistent if I lay it flat and apply it that way?

The only ply I've epoxied and already used on the boat, still looks okay and doesn't seem afflicted in the same way. Unfortunately I can't remember how I painted the epoxy on.

Can I assume that however deficient my brushwork, I'll eventually be able to cover the ply effectively by applying more and more coats, remembering to abrade the dried surface in between?
 
The primary difference between Marine ply and WBP stuff is, I'm told, is that the Marine stuff has been constructed with waterproof glue.

To minimise water penetration after treatment, round all the edges slightly before treatment. That's tedious ( 12 per block ), but not as tedious as removing 'em after 6 months and starting again.
 
Thanks Daydream. It's true that my brushes were of the 'five-for-£2' variety, could be my application wasn't ideal.

Actually I had another look today, and it's not quite as poor as I'd described.

Also, I had reason today to drill a bung-hole through the epoxied ply cockpit bulkhead I installed two years ago, and I was glad to see that the ply itself, which I'd thoroughly coated at the time, seems still to be exactly as good as new despite regularly being awash.
 
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