epoxy coats on plywood. how many?

[kerosene]

I am am making a structural plywood seat to a fiberglass row boat (polyester).

High wear areas will get 300g (1 oz) cloth as will all serious joints be taped with the same cloth. I think those are pretty clear
On cloth areas:
-most likely precoat
-actual glassing
-1or 2 coats to close and smooth the cloth weave. 1st one maybe with silica?

on top of epoxy I will put 2 layers of epoxy light primer and 2 coats of 2 component PU paint.

So my questions:
a) does the above sound OK, overkill or inadequate?
b) How many coats of epoxy do I need in areas that will not get glass but will be painted with at least the 2x epoxy primer (like inside a seat where sun doesn't shine)?
c) how about areas where the epoxy is the only coat? - again not exposed to sun and relatively dry areas, basically spots that are hard to get to with paint after assembly.

thanks.

 

[kerosene]

while at it? is dish soap mix with sponge the best way to wash residue from cured epoxy? how carefully do I need to rinse off the soap?

 

[fallguy]

300g is not 1 oz glass...you are converting wrong

1 ounce glass is quite light for a seat, can help to neat coat, 6 oz will offer a bit more ito strength, that is 200g, not sure which way you are converting wrong

no silica is used unless in a fairing mix and then combined with a low density filler that sands easily

 

[kerosene]

ok, wrong conversion on my part. it is 300g/m2 however..
whatever that is in ounces I guess ~10oz.

was going to use the silica for fairing as I have it at hand but I take it ends up too hard for that use.

 

[messabout]

Conversions for liquids: 28.35 grams = one fluid ounce of Imperial measure. Therefore 300 grams = 10.58 ounces. Life would be much easier if we Americans would adopt the far more sensible metric system.

Brits are only slightly less culpable. Some of them still, mischievously I suspect, weigh themselves in terms of Stones. (The term; stones, has an entirely different connotation among American rednecks)

 

[fallguy]

300g/m^2 • 1 oz/28.37 g• 1 m^2/1.196 yd^2

= 8.84ounces/sqyd, ...9

10 oz/yd^2 • 1.196 yd^2/m^2*28.37g/oz

= 339g/m^2

to be clear

 

[fallguy]

10 oz glass will do a better job for you

 

[kerosene]

yeah it is 300g cloth. Bought in metric. my conversion was wrong thought it is oz/sqft not sqyard.

but...

how many coats is needed to peoperly seal plywood?

and does using epoxy primer on top change anything? ie. can I get away with one coat of epoxy if 2x epoxy primer on top.

 

[Scuff]

while at it? is dish soap mix with sponge the best way to wash residue from cured epoxy? how carefully do I need to rinse off the soap?

Just water is fine. If you use soap and water you need to rinse that off with plain water. I use a scotchbrite scrubby with water to remove it. You can tell when you've removed it as it won't feel greasy. The scrubby also dulls the surface so you can see you've covered the area.

 

[fallguy]

yeah it is 300g cloth. Bought in metric. my conversion was wrong thought it is oz/sqft not sqyard.

but...

how many coats is needed to peoperly seal plywood?

and does using epoxy primer on top change anything? ie. can I get away with one coat of epoxy if 2x epoxy primer on top.

epoxy fills the weave faster than paint

in general the dry mil thickness of epoxy is at least double of varnish and even more than double most paints


Let your eye be the judge. Stop epoxy coatings when the weave vanishes. If you still see weave after two coats, sanding with 60-100 grit may reduce the coatings to 3 versus 4, etc.