Epoxy from about 2001

I bought my CLC kit for the 17 LT about 2001 and got stuck at the point of doing the first epoxy step.  I had a twist in my hull that I was not sure how to resolve.   Then life got in the way, and here I am 12 years later resuming the project!  I have resolved the twist, and am finally moving forwared.

I tested the epoxy and it appears to harden just fine after the long layoff time.  I have already applied epoxy fillets and coated the interior, and am about to embark on the exterior.  

My current dilemma:  The current website how-to-videos presume non-amine blush epoxy, but I am not so confident that my old epoxy is the same stuff.  My old instructrion booklets reference re-sanding the epoxy if you allow the first coat to dry for more than 72 hours. 

Am wondering if I should plan for doing my successive coats of the exterior in quick succession (three days in a row) so I dont have to sand?  

Should I sand regardless, just to be safe?

Or should I just bite the bullet and purchase some new epoxy?

Thoughts, comments, opionions?  Better late than never.

Maybe I will hold the record for longest start-to-finish completion time!

Thanks in advance



7 replies:

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RE: Epoxy from about 2001

  I would bite the bullet. The cost of epoxy is nothing next to the labor you will invest, not worth the savings imo. You could contact the maker of the epoxy and get their take. Good opportunity for you to get non blushing formula.

  The reason for sanding after 72 hours is there will not be a chemical bond between coats applied out of that 72 hr window, all the sanding does is rough up the surface and give the new coat something to 'key' into. The chemical bond is preferred to sanding so I doubt the benefit of both.

  !2 years, wow. you may be hearing more about this...but for now welcome back to building! You may want to test the FG fabric and tape in your kit also and give the wood pieces a good wipe down with denatured alcohol before beginning.


RE: Epoxy from about 2001

If your old epoxy is curing properly, it should be okay. Epoxy resin lasts essentially forever. The hardener often turns brown with age, but still has a long shelf life. The thing to do is to test it, which you have successfully done. If your test had failed, new hardener would have been called for.

Regarding blushing, again, the hardener is the issue. MAS Slow Hardener is non-blushing. Medium and Fast might cause some blush. If you recoat before the underlying layer has cured, you don't need to worry about blush (or sanding). It also gives you a chemical bond, so that would be preferable if your time schedule permits it. If that isn't possible, scrub the surface with water to remove any possible blush and then do a light sanding to enhance a mechanical bond with the subsequent coating.

If you're not sure about the blushing properties of the hardener you have, I would check with CLC, or whoever you bought it from. Good luck.

Old Yeller

RE: Epoxy from about 2001

Thanks to both of you who responded.  Last question:


How soon after the first coat can I start a second coat...?

RE: Epoxy from about 2001

The best time to recoat for a chemical bond is when the epoxy has begun to cure, but is still a bit tacky on the surface. MAS epoxies recommends a "cotton ball test": Dab an inconspicuous spot lightly with a cotton ball. If cotton fibers stick to the surface, it's a good time to recoat. Fibers won't stick if the cure is not far enough along, or has progressed too far. How soon that happens depends on the speed of your hardener, and the temperature in your work area, so it can vary a lot.

Old Yeller

RE: Epoxy from about 2001

Keep in mind that for the boats sold here the "mechanical" bond is as good as the "chemical" bond. They're both stronger than the wood.

There's other advantages to working wet-on-wet or wet-on-tacky, but nobody's boat is going to fall apart because they waited until the base coat was fully cured before applying the next coat. Now high-performance fighter planes, on the other hand...



update: Epoxy from about 2001:

Thanks again.

Update: Two coats on so far (done today, sunday).  First coat took about 6-7 hours before I felt comfortable trying the second coat.  It definitely was still tacky.  It will probably be a minimum of 12 hours before I can do the third coat on Monday morning.  I expect the surface will NOT be tacky at that time, based on the experience of doing the interior seams and fillets.

If I am correct, and the surface is not tacky, and the previous coat was applied 12 hours ago, do I need to give it a light sand first?  

My old manual indicates the sanding is not necessary unless it goes beyond 72 hours, but I am just wondering.

Thanks in advance


RE: Epoxy from about 2001

At 12 hours no sanding needed. Trust the manual.



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