Boat Building Forum

Find advice on all aspects of building your own kayak, canoe or any lightweight boats

Re: Epoxy not curing?
By:Pete Rudie
Date: 4/11/1999, 3:38 am
In Response To: Epoxy not curing? (Gerard Dolmans)

I agree with everything in Paul's most thoughtful post except the warning about the solvent. None of the solvents you can buy in a paint store will harm cured epoxy except methylene chloride. MEK, acetone, xylene, MIBK, rubbing alcohol, none of those things will touch cured epoxy. They will emulsify uncured epoxy though, or improperly metered and mixed epoxy. In fact, the way they test the stuff in the real world is to wipe it with MEK. If it doesn't come off, it's right. Ergo, if it does come off with MEK it isn't right. The danger of a physical test (i.e. it feels dry) is that it can be partially cured, dry enough to fool you, but far enough out of ratio to be well under specified strength figures. With all the work you put into this boat, and considering that you will be trusting it to get you home, it would seem prudent to make certain that the resin is full-strength. Start with a rag and MEK, wearing solvent gloves and a respirator with charcoal filters. Wipe down the whole boat, one small area at a time. That will tell you if any of the surface layer is bad or not. If any of it comes off, concentrate on that area until the entire perimeter is removed back to sound material. Then look for blisters, bubbles and delaminations. These may be uncured material beneath a layer of cured stuff, another trap for the unwary. If you find any, sand them down to bare wood.

Check your pumps or other mixing and metering apparatus. Don't assume that one stroke on the pump gives one complete unit in the cup. Little chunks of debris or crystallized resin can get caught under the check valve and bleed fluid back into the container without burping, and throw your ratio way off. How far off you can be varies with the product. System 3 says you can be 20% over with resin or 10% over with hardener and still be OK, other products may be different. Even though you use pumps, you should still use measuring cups to double check the volumes. Each molecule of resin needs a molecule of hardener to find true bliss, and if that ratio is very far off the end product will never come up to strength, no matter what the time or temperature.

There is a silver lining inside this big dark cloud. Better to find out now, than when paddling in surf and your boats folds up.

Messages In This Thread

Epoxy not curing?
Gerard Dolmans -- 4/11/1999, 12:07 am
Re: Epoxy not curing?
Gerard Dolmans -- 4/12/1999, 12:07 pm
Re: Epoxy not curing?
Stan Heeres -- 4/12/1999, 12:58 pm
Re: Epoxy not curing?
Nick Schade - Guillemot Kayaks -- 4/11/1999, 11:05 am
Re: Epoxy not curing?
Pete Rudie -- 4/11/1999, 3:38 am
Start sanding
Paul Jacobson -- 4/11/1999, 2:10 am