Epoxy/Glass over paint?

[Bretster]

Hi All,
I did the following (below) and found checking occurred in less than a year so am now planning on glass/epoxy to seal exterior of 5x10 TD.

Original treatment (over birch plywood):
3 coats tb2, 2 coats SW Extreme Bond primer, 3 coats SW Emerald Rain Refresh.

My first question is, can I merely sand enough to rough up the surface before epoxy/glass or do I need to sand down to the plywood?

My second question is: based on 4oz fibreglass cloth, does anyone know approximately how much epoxy I might need (~220 sq. ft.)?

Thanks in advance!
Bret


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[RJ Howell]

This is from one that has not tested what I heard and by this I say test it first. If your SW paint is oil based, again only as I have read, can work. There's a qualifier mentioned as to use an oil based polyurethane as a transition. That also comes with a qualifier of age of the oil based paint/condition. I'd test first.

If you paint is not oil based to start with, I see no joy there.

[Pmullen503]

Sanding to wood will definitely work. Glass over scuffed paint? Maybe it will...

[Bretster]

Thanks for the replies. After talking to various people including boat builders suppliers, and an exhaustive web search, meh! But it does seem like the majority thinks stripping back to the plywood is a safer bet. I might be all right with a lesser degree of sanding, but then again, I might not. So, a sanding I will go. Then glass and epoxy and hopefully many years dry and trouble free.

Bret


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[RJ Howell]

I was kinda hoping you'd report something different.. My next build means I'll be adhering in one way or another of XPS and steel ribbing. Steel means oil based something (decision coming) and either a contact or resin adhesive. I'm testing a possible contact type against water infiltration now as it's about to rain here and my sample is out there to get drenched. Worst possible conditions set for the test and hoping for some reasonable results.

What I read sounded possible, yet with those dam qualifiers.. Not that I won't if indeed it's cost and duration advantageous.

Happy you found you choice of direction.Best of on your build.