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jaeger
10-07-2006, 01:14 AM
Hi all,
Some time ago I decided to build the 6 hour canoe to get some practice for a bigger sail design hopefully to come in the future. I used fir ply and fir trim. The construction went well, barring the gun'l split. Next I coated the entire canoe, in and out, with West System 105/206 epoxy followed by 2 primer coats and 2 finish coats of a marine paint from Home Depot, I don't remember the brand. The paint was sprayed on. Well, I goofed. I forgot about the blush before painting so naturally the paint didn't stick, and it looked so nice for a while. So once I finished the appropriate amount of cursing a sanded of all of the primer and finish coat, wiped the hull down with acetone followed by alcohol and repainted. I thought I was all set but the peeling has come back. So now the 6 hour canoe has become the 6 year canoe (stop laughing Matt, :)) and I'm about ready to give up. What can I do? Where did I go wrong? Any suggestions are greatly appreciated. It would be nice to see her float :|.

Thanks, Bruce

Jim Mathieson
10-07-2006, 07:04 AM
You say that you sanded the paint off,sounds like you may not have sanded the epoxy coating everywhere....?,
I'm just assuming the peeled parts of the hull were not sanded,but only rubbed with acetone and alcohol.....?
Cured Epoxy won't stick to paint without sanding.

jaeger
10-07-2006, 10:56 AM
I used a disc sander to take it down to the epoxy. I thought I got a little into the epoxy, enough to scuff it, but maybe not. Am I correct that the solution is to sand it all down again and start over? Do I need to go to bare wood?

Bruce

capt jake
10-07-2006, 11:01 AM
As long as you are down to epoxy, you should be good to go. :)

Thorne
10-07-2006, 07:34 PM
Maybe the epoxy didn't fully cure? Try sanding into the epoxy a bit, then wipe to clear any blush, then let it sit and cure/breathe for a week or so. Wipe again and let dry, then try a paint sample.

How long does the paint last before peeling, and is it related to getting it wet / use? Could it be the paint? Any chance of trying a different paint on a test section?

Frank Wentzel
10-07-2006, 10:59 PM
According to old posts from people who are supposed to know epoxy coatings, and also, I believe, in some "System 3" literature, paint adhesion problems have to do with unreacted amines from excess hardner in the epoxy layer. You have to remove the unreacted amines. In most situations a water wash will do it. Not acetone, not alcohol nor paint thinner but water. In a case where the might have been a larger amount of unreacted amines do to excessive hardener, a wash of acetic acid (white vinegar) will give further assurance of amine removal. If there is sufficient unreacted hardener in the epoxy film, sanding will not eliminate the amine problem but only expose more amine laden epoxy. Water and a vinegar wash (followed by another water rinse) should do the job.

/// Frank ///

Dave Carnell
10-08-2006, 07:40 AM
It's too late now, but why did you gild the lily of such a simple project with the cost and time of epoxy coating. Anyone with a similar project should just prime with 100% acrylic latex exterior primer and finish with 100% acrylic latex house paint.

Jim Mathieson
10-08-2006, 09:17 AM
My Nephew made the same six hour canoe and coated his with a non blushing epoxy, Premium Blend from Paul Omans Progressive Epoxy Polymers.
He's had no problems with paint.
Being a ply boat I think it's a good idea to coat with epoxy,

jaeger
10-08-2006, 01:29 PM
To answer some questions:
I used the pumps for the West System which should have measured out the right amounts. I did see an air bubble occaisionally while pumping so maybe the mix wasn't quite right.

The paint started peeling within a couple of weeks the first time, maybe a couple of months the second.

I don't think wetness was the cause. The hull was kept in the garage during that stage. Possibly humidity, I'm in central Florida.

The gilding was for 2 reasons. Fir ply is notorious for checking, I was hoping to avoid this. So far very little checking has shown up. Second, I am using this project as a training ground for a bigger project to come.

pipefitter
10-08-2006, 02:51 PM
Here's another thought. Interlux suggests using their 401/404 primer over epoxy encapsulates as it is more forgiving to amine issues when coloring with one part alkyd paints. When using a primer,you can tell if you have adhesion problems when sanding as it will not sand to a fine feather edge. I painted directly over raw epoxy with brightsides and had no issue but I washed the boat 5-6 times with amonia and water before sanding and after with the aid of a scotchbrite pad.Then before paint,I wiped down the hull with mineral spirits and clean white paper rags until nothing transfered to the rags while turning them frequently and tossing them and replacing often. The initial key for primer should be no finer than 180 grit on the epoxy and no finer than 320 between coats of paint for one part paints. Before you commit to totally painting,try a small patch and let "totally" cure and then sand it off and see if you can get a feathered,semi transparent edge on the test area. This will tell you if you have adhesion issues before painting the whole boat.

Solvents such as acetone or laquer thinner will actually bring more trapped amine to the surface and you can tell because it will make the surface somewhat tacky again. The advantage to washing with water is you can rinse with plenty of running fresh water.Acetone and other fast dry solvents just move the contaminants around more than remove them.

Frank Wentzel
10-08-2006, 11:22 PM
Bruce
From what I have seen a layer of epoxy without glass or other reinforcing material will not stop checking. I think it will delay checking more than any type of paint but to stop checking you need reinforcement material in the epoxy.

/// Frank ///