Epoxy - Hairline Cracks

[schlaboatnic]

The plans for my 17' Kayak call for sealing the deck with 1 or 2 coats of unthickened epoxy prior to varnishing. If 1 or 2 is good, then three should be better, right? Well, now that it has had time to dry thoroughly, I checked it out this morning and found hairline cracks over the entire deck. Should I have stayed with just 1 or 2 coats? Did I wait too long for the 3rd coat? Not long enough? Any suggestions how to fix? I am using Fiberbond epoxy at a 2:1 ratio. I would insert a pic. if I could figure out how! Thanks for any insight.

[Stephen Hutchins]

Is there a general direction that the cracks run? -Fore and aft? Athwarthships? The cracks are in the epoxy?

[schlaboatnic]

They run all directions, like a cracked egg. They don't appear very deep, like they are limited to the 3rd. coat. I've got a pretty good picture, but still can't figure this picture posting thing out.

[Jim H]

Too bad The Chemist is no longer around, I'm sure he would figure this one out. 2:1 ratio, IIRC, is supposed to be slightly more flexible that a 5:1 epoxy like West. I've never had it happen to me regardless of the number of coats of West.

[alteran]

Go to misc. non boat related and see the thread, "What is art?"

Tell them about your new art form, sell it on E bay for big bucks and start over. smile.gif

Hey! its a thought.......

[RonW]

Spider web cracking is due to stress. In this case contraction. The first coat was probably a little thick, and before it thoroughly cured you put a nice second thick coat on, and before it completely cured you topped it off with a nice thick 3rd. coat. The first and second coat are curing and contracting slightly and something has to give. Wait several days and sand about 1/3 of the epoxy off, which should remove the spider webs, and refinish lightly. It also shows that that type of epoxy is not good for a thick buildup.

Too thick ( and/or too quick)of a buildup with certain products will lead to fracturing or cracking and spiderwebing, just what you have.

[schlaboatnic]

Thanks much for the replies. What Ron says makes sense. It appears that a light sanding with 150 grit takes it down enough to get rid of the cracking effect. What if I just do that then go with the varnish, forgoing any more epoxy?

[kc8pql]

Originally posted by Jim H:
I've never had it happen to me regardless of the number of coats of West.I've never seen it with System Three either.

[RonW]

I don't think you need more epoxy, just varnish.

A little is good and more is better doesn't always work. That is why they make wax strippers, to start over again.

With some stuff it is not only the thickness, but the time frame between coats. Coating too quickly can cause problems that using the same product and building up with proper drying times between coats and it works fine.

[Bruce Hooke]

I would also avoid that brand of epoxy in the future...

That said, another thing to do would be to call up the manufacturer and get their opinion on what happened.

[P.I. Stazzer-Newt]

Seen that effect with a panel which was disturbed - and slightly flexed - while the epoxy was curing.
Sand lightly and paint with something opaque.

[Jim H]

I thought about this some more last night. The last time I coated a hull, I let each epoxy coating get to the "green" stage then recoated. It saved me the extra sanding and cleaning.

[kc8pql]

I try to recoat within 24 to 48 hrs. System Three says that if a coat is applied within 72 hrs. of the last you get a chemical bond between the two. If applied after the previous coat has completely cured, you get a mechanical bond.

Ken

[schlaboatnic]

My recoats were done approx 24 hrs apart, per the instructions from the supplier. I am suspect of this particular brand of epoxy.