How to coat plywood with 2-part epoxy resin

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Plomong

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I have a dozen or so pieces of plywood about 6 inches square that I want to coat with 2-part epoxy resin on all 6 surfaces -- 2 flat sides and all 4 edges.

What is the best way to go about this so as to waste the least resin possible ??

A) Hang them by a temporary hook or nail inserted in one of the edges and paint them hanging from a shed rafter ??

B) support them on some form of wooden blocks like Lego bricks and do top and edges in one go, doing the bottom surface in a second session 24-hours later ??

Any hints or tips welcome

Plomong
 
Plomong said:
A) Hang them by a temporary hook or nail inserted in one of the edges and paint them hanging from a shed rafter ??
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IMHO this. Also, if you want good penetration of the epoxy into the wood then consider thinning the mixed epoxy with no more than 10% methanol or acetone.

I assume you are already aware that epoxy itself is not UV proof so will need coating with a UV barrier like varnish or paint if it is to be exposed to the outdoor life ?

Hth,

Boo2
 
Boo2 said:
...consider thinning the mixed epoxy with no more than 10% methanol or acetone.
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I've read enough on the subject to be persuaded that this definitely isn't recommended...it sounds good in theory, but if the bond with the wood is good, the waterproof coating formed by the epoxy is quite sufficient, given a few coats...there are reasons why thinning doesn't improve penetration, or why penetration isn't necessarily beneficial; here is some explanation from West Systems:

Adhesion in all but the highest density wood is not enhanced by deep penetration of the glue into the wood. Research performed at the Forest Products Laboratory showed that adhesion to birch was increased slightly by using thinned epoxy. In lower density wood species like Sitka spruce or Douglas fir, the weak link is the cross grain strength of the wood. It does not matter if the epoxy penetrates 1/4" into the wood or 5/1000".

The strength of the wood, the amount of surface area and the adhesive ability of the glue determine the strength of a glue joint. Most types of wood glue do not penetrate deeply, yet, if used properly, they can exceed the grain strength. Epoxy is no exception.

Water resistance of a piece of wood is not enhanced by deep penetration. Wrapping wood in plastic makes a pretty good waterproof seal without any penetration at all. Likewise, an epoxy coating on the surface is more water-resistant than a thinned epoxy coating that has penetrated deeply into the wood because, in most instances, the epoxy thinned with solvent is porous.
 
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Bring the wood into a heated environment and let it warm up. Then when you take it out to the cold shed and paint the epoxy will be drawn in by the contracting air in the wood. Put 3 screws into a piece of scrap so that the points stick up and then paint one side then put on the screws while you paint the others. It will leave a few virtually invisible points on the wood when it dries but it helps avoid drips on the flat surfaces. Apply plenty to the end grain.
 
pmagowan said:
Bring the wood into a heated environment and let it warm up. Then when you take it out to the cold shed and paint the epoxy will be drawn in by the contracting air in the wood. Put 3 screws into a piece of scrap so that the points stick up and then paint one side then put on the screws while you paint the others. It will leave a few virtually invisible points on the wood when it dries but it helps avoid drips on the flat surfaces. Apply plenty to the end grain.
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I agree with this advice. Helps if the epoxy is warm too.

Colin. Www.solocoastalsailing.co.uk
 
dancrane said:
Adhesion in all but the highest density wood is not enhanced by deep penetration of the glue into the wood. Research performed at the Forest Products Laboratory showed that adhesion to birch was increased slightly by using thinned epoxy. In lower density wood species like Sitka spruce or Douglas fir, the weak link is the cross grain strength of the wood. It does not matter if the epoxy penetrates 1/4" into the wood or 5/1000".

The strength of the wood, the amount of surface area and the adhesive ability of the glue determine the strength of a glue joint. Most types of wood glue do not penetrate deeply, yet, if used properly, they can exceed the grain strength. Epoxy is no exception.

Water resistance of a piece of wood is not enhanced by deep penetration. Wrapping wood in plastic makes a pretty good waterproof seal without any penetration at all. Likewise, an epoxy coating on the surface is more water-resistant than a thinned epoxy coating that has penetrated deeply into the wood because, in most instances, the epoxy thinned with solvent is porous.
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Interesting but I don't think the grain strength is relevant to the OPs coating application. The part about referencing the porosity of the thinned epoxy is also interesting but personally I would ignore that and apply the first coat thinned anyway. Subsequent coats could be unthinned but I would just feel better about more penetration in the real world of abrasion etc. I guess WEST did write the book though...

Boo2
 
pmagowan said:
Bring the wood into a heated environment and let it warm up. Then when you take it out to the cold shed and paint the epoxy will be drawn in by the contracting air in the wood. Put 3 screws into a piece of scrap so that the points stick up and then paint one side then put on the screws while you paint the others. It will leave a few virtually invisible points on the wood when it dries but it helps avoid drips on the flat surfaces.
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Temperature forecast is for 27 Celsius in the early afternoon.

pmagowan said:
Apply plenty to the end grain.
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Will do.

Thanks, to all who answered,

Plomong
 
I put three coats on in one sitting on my new truss components and just left it to cure on release film (http://www.ecfibreglasssupplies.co.uk/p-1674-30-micron-red-release-film-15mt-wide.aspx) so it didn't stick. Did mean handling the slippery suckers though:

S1GvJyAl.jpg


If you have further finishing to do (painting, secondary bonding to glue it together etc) consider using peel ply over the top of the epoxy. Means no amine blush and no sanding afterwards to get it ready for the next process - best gift you can give yourself when working with West is Peel Ply!! (http://www.ecfibreglasssupplies.co.uk/p-374-peel-ply-1-mt-wide.aspx)

UqnSIz8l.jpg
 
IMHO, the best way to thin epoxy is usually heat.
Anything else, RTFM, as there are many different 'epoxy' products, blended for different purposes.
 
I have a 1.2x1.2x18mm piece of WBP ply, that I'm going to place under my dingys parking place, to make it easier to manhandle it in and out, stored upright, my question, is the application of 2 part epoxy resin, one coat, going to be better than yacht varnish? It is going to be exposed all the time, also dragging dingy in and out will no doubt scratch the surface.im hoping done properly the ply might last a couple of years.
 
Binman said:
I have a 1.2x1.2x18mm piece of WBP ply, that I'm going to place under my dingys parking place, to make it easier to manhandle it in and out, stored upright, my question, is the application of 2 part epoxy resin, one coat, going to be better than yacht varnish? It is going to be exposed all the time, also dragging dingy in and out will no doubt scratch the surface.im hoping done properly the ply might last a couple of years.
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Depends on the ply.
Some will survive fine on its own, some will not.
Is it going to be sat on wet ground?

You might do better to consider different materials?
Maybe nail on a bit of old lino?
I have a bit of old carpet on the concrete under the transom of my sailing dinghy, I change it every couple of years. Astroturf might be better?
 
Binman said:
I have a 1.2x1.2x18mm piece of WBP ply, that I'm going to place under my dingys parking place, to make it easier to manhandle it in and out, stored upright, my question, is the application of 2 part epoxy resin, one coat, going to be better than yacht varnish? It is going to be exposed all the time, also dragging dingy in and out will no doubt scratch the surface.im hoping done properly the ply might last a couple of years.
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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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