Drying the hull

[PANorth]

Over the past year I've been doing a major blister repair job for which I've sought advice under different entries in this forum. I had always heard that one way to deal with blister is to simply dry out the hull. Well, in the process of filling our ground-out blisters we discovered three that had not been ground deep enough - there was still liquid under deeper layers of laminate. I marked them for additional grinding, later, so as to avoid contaminating the rest of the places I was filling. I assumed that after a year, including a hot summer, these blisters would be dry. It turns out that one of them held it's fluid. So there is a lesson - even after a year of drying, including a couple months of hot weather, a hull may hold onto significant moisture.

 

[David Vaughn]

We are looking at a moderate blister repair job on our E31, in the not too distant future. I've read through some of your posts, and was wondering, in retrospect, was there anything that would have indicated earlier on that those specific spots were not drying out completely?

 

[PANorth]

Tenn-Tom, that's a good question. You saw the pictures so you know we did a lot of grinding. Perhaps if we had sounded (tapped) each spot after we had removed the blistered material we could have told that there was more to do. We discovered the continued moisture when we heated the sites before applying epoxy. Moisture bubbled up very quickly. On tapping they sounded hollow. It was a few months later, with air temperatures in the 80s that I ground them out further and discovered that only one still had a pocket of water, which was deep within the laminate.

 

[David Vaughn]

Interesting that you found the moisture when you heated those sites. That's making me wonder if careful application of a heat gun or something on the worst of the blisters would speed our process. Or at least help us check, along with thorough tapping, that each area is properly dry.
We will have to do this in a marina yard, so it will matter about the time. Hoping it won't be too bad, but won't know for sure till we start grinding.

 

[PANorth]

We bought this boat last summer knowing that there were blisters to be addressed. We did not learn the extent of it until we removed the bottom paint. It turned out that small blisters, that did not show through the bottom paint, were everywhere. Fortunately for us, we had parked the boat on our boat partner's lot for a refit, so storage is free. We are approaching the end of the project.