Epoxy coat times

I'v been reading through the epoxy instructions for coating the fiberglass (WD10) and they imply I should put the first coat on and let it harden before floating the 2nd (and if needed 3rd coat) on.

The boaters I know (who have glassed more things than I'll ever do in my lifetime) are suggestiong I float the 2nd coat on after the first coat epoxy is started to set and is tacky (3-4 hours), not wait 24 hours like the manual says, otherwise i'll be left sanding fiberglass to get it prepped for the 2nd coat.  It should be just as strong, and be more efficient with my time/effort.

Any comments?


2 replies:

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RE: Epoxy coat times

The sanding requirement comes from the fact that epoxy doesn't bond well to a smooth chemically-neutral surface. So if the time between coats is long enough that the previous coat is no longer chemically active, it needs to be roughed up for the next coat to adhere properly. The cure rate is dependent on temperature and the particular chemistry used in a manufacturer's resin blend. Cured only to tacky guarantees that it's still chemically active.

As long as you don't let it cure to near completion before the next coat, you won't need to sand it. Depending on the brand of epoxy, that could be up to 3 days. So tacky or 24 hours, either should be fine.

To be absolutely certain, go to the epoxy manufacturer's website and check out their documentation. I got the 3 day figure from System 3 for their epoxy

Have fun,

Laszlo

 

 

RE: Epoxy coat times

I'm using the West Systems, and after reading it + alot more online i'm going to not let it totally cure and aim for my layup in 2 or 3 thin layers back to back without it toally setting.

That seems to confirm what I was going to do and in my attempt to "check twice, epoxy once" this should help out.

After reading about a few build experiences i'm also going to dryfit the fiber cloth, take it off and then wet coat the wood surface, finally laying the glass on top and start to roll/squeegie it on.

I'll let you know how it goes!

 

 

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