blister repair -- advice needed

[pegasus1457]

The hull of my 1980 Pearson 32 was bead blasted today. Once the accumulation of years of bottom paint was removed it became apparent that I have hundreds of small holes to deal with. I presume these started out as osmosis (blisters) and they popped.

I plan to wait as long as possible before repairing them to allow any trapped moisture to escape -- probably 2 months. Ultimately I will apply a proper barrier coat.

But how do I deal with these craters? Do they need to be ground out before filling? What kind of product is recommended for filling the holes?

Thanks for any advice.

[camaraderie]

This will give you all the info you will need.
http://www.zimmermanmarine.com/docs/blisters%201.pdf

[stm]

Also check out Zahnheisers marina web sight(spelling) in Solomans Isle, Maryland. They have an extensive explaination of blisters and repair.

[pegasus1457]

Originally Posted by stm

Also check out Zahnheisers marina web sight(spelling) in Solomans Isle, Maryland. They have an extensive explaination of blisters and repair.

Zahniser's site is enough to make your blood run cold. The only repair they are willing to discuss involves a peel, relaminating, and a barrier coat. Cost: about $20K for my $20K
boat. There has to be a more moderate approach.

[soulesailor]

Pegasus~ are you sure they are blisters that popped? If you have craters after a blasting they may have been air pockets from the resin not fully penetrating the cloth in the original lay-up. I've seen this on my friend's boat. They were everywhere, dry as a bone. Originally they were bubbles between the cloth laminate and the inside of the gelcoat, very blister looking. The blasting might have blown off the gelcoat side of the bubble, leaving you with the craters. If this is the case you don't have to wait for your hull to dry, you can move right in and get to work.

[Freesail99]

Unless you have a heated area to work in, I wait till mid March to work with the epoxy.

[pegasus1457]

Originally Posted by soulesailor

Pegasus~ are you sure they are blisters that popped? If you have craters after a blasting they may have been air pockets from the resin not fully penetrating the cloth in the original lay-up. I've seen this on my friend's boat. They were everywhere, dry as a bone. Originally they were bubbles between the cloth laminate and the inside of the gelcoat, very blister looking. The blasting might have blown off the gelcoat side of the bubble, leaving you with the craters. If this is the case you don't have to wait for your hull to dry, you can move right in and get to work.

After my initial panic, I began to wonder the same thing. I had my previous boat bead blasted about 9 yrs ago, and there were no such blowouts.

But I am inclined to agree with your diagnosis, especially since the surveyor went over the hull below waterline with a mallet and a moisture meter, and I would be surprised if he missed such widespread water intrusion.

So maybe the difference between the previous job and this one was the technique used in laying up the hull (different manufacturers) or the guys who did the blasting were more aggressive this time. I recall that last time after the blasting job I had a whole day's sanding to remove the remaining islands of bottom paint - all small, pimple-sized. This time the only bottom paint remaining is under the jackstands.

If the craters are not blister-related, then the repair consists of one afternoon with a spatula and epoxy filler...

[sailingdog]

They sound more like small gelcoat voids, rather than osmotic blistering. IF they were osmotic blistering, you'd have them weeping a rather nasty acidic mixture. If they're dry on the inside, and it sounds like they are, they're layup voids.

[camaraderie]

Move the jackstands a bit and by hand get down to the gel coat and see if there are indeed blisters...and if they weep when you poke them. If not...fill 'em & barrier coat and go on your merry way!

[sailingdog]

Wear eye protection when doing this, because if they're osmotic blisters, you don't want to get the liquid in them in your eyes... and if you're poking at the blisters and break a new osmotic one open, the liquid is generally under some pressure and will spray quite a distance.