How to deal with old sunburned epoxy repairs?

I've got a bunch of different West System projects the got left out in the sun long enough to burn the resin out of the fabric on the surface. This is most obvious where I was using peel ply. Any thoughts on how deep the repair has been degraded? on the non structural stuff I was going to power wash the areas and recoat with epoxy. I have some more structural work that's gone yellow, but I'm assuming a 1/2" layup wouldn't be significantly degraded, but I'd rather not regrind to see how far the 'Yellow" go's. Any thoughts? thanks
 

cyclone

Super Anarchist
1,438
676
Maine
Quick phone call has always helped me
 
I tried that a while back and the tech I talked to hadn't heard that question before... "so maybe you could like sand it" ... I have called before with bigger problems and talked to a very sharp engineer, who agreed that I may be asking to much from 105. This was before G-Flex, which probably would have been the solution if in production.

So I'm just fishing for some boat yard wisdom. I personally have done the ninja fade before having to give an opinion when shown a sunburned composite experimental aircraft.
 

Kenny Dumas

Super Anarchist
1,217
461
PDX
If it’s not brittle, then it’s ok. Maybe try gouging with a screwdriver. If it feels like normal material, coat and cover.
 

CaptainAhab

Anarchist
844
230
South Australia
but I'd rather not regrind to see how far the 'Yellow" go's.
What other option would there be? Bonding with epoxy to an obviously damaged area would be stupid. You need to do prep work regardless. The resin is burnt out of the fabric. At the least, you need to grind off that top layer of glass and replace with more. There is no easy way jout. No one is going to say "She'll be right" and bury it under filler.
 
I hear you. From experience, do you have any feeling for how UV degradation penetrates? The ugliest spots are on the exterior of a canoe where I used Peelply and I think a squeegee. So basically zero resin floating over the glass, and the "soft" resin has been striped away with a power washer. The patches are full thickness, laminated from both sizes, probably 1/8" of hull thickness, and very much translucent. The interior shows no degradation. This particular canoe will get another round repair before getting faired and painted. The "structural" stuff is on a cruising boat under the waterline, that hasn't been in direct sunlight and just needs to hold paint.
 

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