Blisters in barrier coat

[lost soul]

I pulled the boat after several years and as I was scraping the barnacles I started to notice small blisters.....

The boat was epoxy barrier coated in 2008 and has been in the water until this march, in Florida. There were a few hundred blisters about 1/4 inch. I sanded each one and they went into the gel coat but never penetrated into the laminate.

I call them barrier coat blisters. They were sanded out and filled with West System epoxy. I used just the resin and then came back with a resin and micro balloon filler. I sanded the spots and the thickness is very thin.

Now the bottom has a lot of spots but is otherwise ready for paint. I am wondering what to, do if anything.

-----A little more history: The boat is a 1974 Tartan 34. It never had a blister as far as I know. I have owned it for 20 years. The bottom was
"washed out" and was peeled and re laminated with vinylester in 2001. Gel coat was applied over the new laminate and anti fouling over that. The boat was in the water, in South Florida until 2008. Then it was hauled and there was no sign of blisters.

There were lots of tenacious barnacles that were scraped and sanded off. The gel coat was thinned in many places, so I decided to do an epoxy barrier coat as a primer to protect the gel coat (and laminate) from future wearing from sanding. I used rolled on West System epoxy, cant say how many coats or the thickness. I will say that I did a terrible job, with runs and sags all over the place. I did not know this until the haul out. I spend the entire month sanding the hell out of the bottom. The epoxy cured with a "mottled" finish. I sanded and sanded and would sand thru one layer of epoxy, yet still not have the anti fouling sanded off. Picture attached. Anti foul layers are brown and grey. Gel coat is whit and grey.



SO what should I do? I am thinking I need to use a primer to protect the bottom. But I am worried that I will have the same issue with blisters. I could use a non epoxy primer but epoxy is very hard.
I was thinking of Sea Hawk Tuff Stuff. I looked at a Sea Hawk video of the Tuff Stuff application, but was not impressed. The epoxy went on with a texture and not at all smooth....

Any ideas, experiences, and recommendations?

thanks!!!

 

[shemandr]

So am I reading correctly that your boat was in the water for 9 years? I would think that it would be unusual to not have blisters after that long in the water.
So far as I can tell you have opened the blisters, dried them and put thickened epoxy in the holes. I would sand them smooth, apply a couple of coats of barrier coat and then bottom paint and go on with my life. I might not bother with the barrier coats but there probably is some value there.
Yes, you probably will have blisters again. But if you get 9 years I would call that a win.

 

[lost soul]

So am I reading correctly that your boat was in the water for 9 years? I would think that it would be unusual to not have blisters after that long in the water.
So far as I can tell you have opened the blisters, dried them and put thickened epoxy in the holes. I would sand them smooth, apply a couple of coats of barrier coat and then bottom paint and go on with my life. I might not bother with the barrier coats but there probably is some value there.
Yes, you probably will have blisters again. But if you get 9 years I would call that a win.

Yes, you have it right, 9 years in Florida water. Actually it has been in the water continuously since 2002 with only a 2 month haul in 2008. Now it has been out since March. I hope it is good and dry by now.

I agree with your thoughts. I hope I would wait another 9 years, 5 maybe.

Thanks for the reply.

 

[Gunni]

West Epoxy neat is not a satisfactory barrier coat primer. You have learned the hard lesson of taking short cuts and using hear-say solutions with this very tedious job. For many many years the boating industry was flummoxed by blistering and many failed solutions were tried. Those are the old days. We now have proven barrier-coat primers specific to the job and you have to prep and apply them properly. It sounds like your epoxy failed and blistered. But you have another problem too, micro-balloon filler. Although it is easier to work with it is not a good filler for underwater repair. Cabosil or similar mineral filler is the thing to use. Use one of the purpose designed barrier-coat primers and get the recommended build thickness on the barrier coat.

 

[DArcy]

We had a product that was built with vinylester resin but for some reason had polyester gelcoat over it. As expected, the polyester soaked up moisture and caused problems. We ended up going through quite a bit of testing on various moisture protection coatings when immersed in warm water. There were a couple of epoxies and gelcoats but the product that worked significantly better than any other for minimizing moisture absorption was InterProtect 2000E. If my boat was in the water year round that is definitely what I would use. It really does work as advertised.

 

[Maine Sail]

Part of the problem, and one people very, very often make is inadequate hull dry out time before the barrier was applied. This leaves moisture between the two layers that will try to escape.

 

[lost soul]

Could be that my hull was not dry enough. Probably it was not dry enough. Gel coat was wet?
I would have been just fine if I did not put the barrier coat on.
I guess I will use some epoxy barrier coatt as a primer/sealer. A vinyl ester laminate does not need a barrier coat from what I have learned.

If I get more blisters I will use cabosil next time.

Thanks for the comments!!