Blister Repair Project

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Senior Member
Oct 6, 2007
Nothing is as scary to boat buyers than to hear the surveyor say "This boat has blisters" .* In my business as a Broker,* I hear it all the time.* It will kill a boat deal faster than anything.

But in my role as a trawler owner, I knew my baby had developed some blisters over the past few years, but getting good reliable information about what to do about it, and what it costs was a mystery.*

So with my laptop in hand, I set out to find what was available on the Internet..NOT MUCH I found.

I did however confide in my friend at my local boat yard who told me about Tom, with Boat Savers, A Gel Coat Removal company.* A couple phone calls and we were set.

But without me having to go into all the details right here, I started a chronicle on my Cruising Blog that will explain the causes up to and including the peeling and repair.* Go to my blog below and go to May, 2008 to read where we are to date on Blisters and Hydrolysis.* Here you can see photos of how it works, prices, everything you'll need to remedy your problem if you've been thinking about it.

I just met with Tom this morning and he's satisfied the hull's dry enough to begin putting my trawler back together.* I can't wait!
Uh, we have a glitch here. I can't see the original post, but I can see the first sentence in preview....

Well, once I posted the above, I could see the original note. Here are some sites with info. on blisters and repairs. Long story short, I used the HotVac system to post-cure my hull. Worked great but took a long time since I had a cored hull.*(.PDF file)

-- Edited by Keith at 16:16, 2008-07-30
There are blisters and there are BLISTERS. I'm glad I'm not a broker and have to deal with them.* I've seen a few rip off artists when it comes to blisters and there repair. I've never seen a blister sink a boat.
We just pulled the Eagle and have several hundred blisters less than dime size which are not big enough to be a concern/repared.* When blisters get to the size of a quarter is when they should be replaired.* We had three quarter size bottom paint blisters that were repaired.*

Many blisters are just the bottom paint and not the hull.* To thick of bottom paint*is many times the cause.* Bottom paint and/or blister under the size of a dime do not have to be repaired.* So before*doing a big blister repair, determine the size and the cause of the blisters.*
I've found that the biggest issue involving blisters is not the boat itself but the lack of understanding by boat buyers and or owners. They are nothing to be scared of, and as RollsDoc says, they have yet to be shown to sink boats.

What is missing in the thought process is that blisters are a symptom of more troubling issues, structural deterioration. All boats having blisters are having hydrolysis within the hull; but just because you do not have big blisters does not mean there is not hydrolysis going on. If left long enough without attention, you WILL have troubles. Generally, the size and number is indicative of the extent of the troubles.

For instance, I had a number of quarter sized blisters on my hull, but when we peeled the hull, the worst damage was occurring where there were NO blisters. An area about 8 inches by 24 inches will have to have the glass removed and replaced on the stb side just below the waterline about amidships.

Go check out my cruising blog, you can see it there.

Those blisters have been there for at least 10 years, and do not seem to be changing, since I do the bottom painting sanding/prep and painting.* The ones I have broken are bottom paint.* I had an out of the water survey done just incase the insurance company requested, and he rap on the complete hull for about 30 minutes and found nothing.* The surveyor was not concerned either.*
I photo document pretty much everything done on my boat. Here are a few pix out of hundreds from my blister repair project. Now THESE were blisters! After fixing them, not a single one has appeared since.


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Nice job Keith. It almost looks like the OEM glass job did not fully wet out the fabric???
Possibly, but I think we were just shaving off the tops of the mat, and that's why it looks that way in places. Here's what we put back after drying:

3 sessions of 1.5 oz. fiberglass mat with vinylester resin
2 coats Interprotect 1000 - High build epoxy primer
2 coats Interprotect 2000 - 2 part epoxy barrier coat
1 heavy sweep Interprotect VC tar2 - Watertight 2 part epoxy putty
3 coats Interprotect 2000 - 2 part epoxy barrier coat
2 coats antifouling - Petit Trinidad SR (4 gallons).

Blisters begone! And stay gone.
Blisters are an indication of internal fiberglass hydrolysis. Once it begins, you have the problem forever unless you take steps to correct it. Patching a few blisters make look better, but you still have the problem.
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