I am sorry to be bouncing around but my de-laminated deck discussion turned to one on  blisters - so I'm starting this new thread. I wrote a long reply - in the Ask Bud forum that I'm not going to repeat. This is really a show and tell -- of a failed barrier coat - done in 1991 - and with a heavy epoxy. It might have done well for a while but now it is coming off in large ugly blisters. The good news is that almost none go beyond the "mystery blue layer" There is a very thin coat of blue - right before you get to the laminate. There is white gel coat over that and then the heavy epoxy barrier coat and then the bottom paint. After popping about 50 blisters -- only like 2 have gone beyond the blue layer into the laminate.

I can pry much of the blistered layer off - but I really can't do that for the whole bottom. I'm thinking I would like to go down to the blue layer and then light sand that to expose bare laminate to breath. The one photo show where I did this with a grinder.

Is that blue layer a special coating that was applied to the back of the gel coat prior to the laminate? It is very thin - so I'm not sure I need to completed removing -- but I do want this hull to dry out -- so maybe sandblast down to the blue and then lightly sand till there is very little blue?

I am happy the the actual hull laminate appear relatively dry and sound -- but if I'm going to do this I want to you this right. My guess is that this blister job probably show signs of failing 10 years ago.

http://i1215.photobucket.com/albums/cc520/jengle53/blister2.jpg

http://i1215.photobucket.com/albums/cc520/jengle53/blisters.jpg

http://i1215.photobucket.com/albums/cc520/jengle53/blister1.jpg

I'll be attacking this job soon -- aren't boat fun?

Hey Jim, how did this turn out? I have a similar situation.

I've had hull #700 for 15 years with zero trace of blisters until last summer. All of them are just under the barrier coats the previous owner put on which are layers West System plus Interlux 2000. I've had two moisture meter readings and both show the laminate wet but they never ground through the barrier coats. I haven't had it profiled yet, where they grind a 6" to 8" diameter area down through layers of roving until they get to dry layers to figure out how much has to come off. Everything I'm reading says you can't really dry a wet hull - the best solution is take off the wet layers and replace them.

 

http://i1215.photobucket.com/albums/cc520/jengle53/barehull.jpg

The posted picture is after the peel which still left a fair amount of sanding to get rid of the ridges. I did not want the yard to go too deep on the peel and they did a great job. After sanding, the surface is smooth and very dry - and will be ready for a few spot repairs and then the barrier coats. I was pretty amazed at how good the bottom looked - considering the ugly barrier coat failure and what I have seen of other boats.

All the blisters (except maybe a half dozen) were between the epoxy barrier coat and the gel coat -- but the gel coat was definely gone. There was a separation between that black/blue layer and the white -- but not beyond the black/blue.

I believe peeling is the way to go -- yes it must come off -- but underneath does look very good. The peel was done July 2011 so she has been drying out for a while -- but she could have been barrier coated in the Fall if I had had the time.

You do need to do the test grind -- and hopefully your situation will be no worst than mine. Trying to read moisture through the mess of failed barrier coat is not going to tell you anything.

Good Luck!

Jim