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Closet Powerboater
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When cruising the yards and sales lots, some of the potential boats I want to buy are known to have blisters. I also know that blisters are common in 80s vintage boats because of various production issues. I was raised to believe that blisters are boat leprosy. Simmilar to wood rot, they will multiply and destroy the boat. If the boat's got blisters, walk away!

Recent reading on the subject reveals several articles from supposed experts saying that blisters are in fact no big deal. How can that be? If they're no big deal, then why does everyone worry about them so much?

What's the verdict? Cosmetic, or a fatal disease?


MedSailor
 

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Most boat blisters are hype, unless the hydrolysis, etc, is deep into and affects the structural roving layer of the laminate. Blisters affect mostly the cosmetic matting layer of a laminate structure, the matting is a 'cushion layer' so that the gelcoat remains stable during the full term / many years 'curing process' of the resins.
Hull Blisters on Boats and Yachts - by David Pascoe, Marine Surveyor
 

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Most are cosmetic, some - especially if left alone for decades could allow water to infiltrate to the glass and then some repair would need to be done. As far as compromising the hull, I have never seen or heard of one failure.

too much ado about nothing. I have known several who spent $$$ to remove them, it is a labor intensive process with no guarantee that things will be better. A LOT of misinformation and "bar room" advice about them.

Speak with a surveyor or marine architect, if you were on Chesapeake, I would steer you towards Hartge Marine, they have quite a bit of experience with them. All the rest is hearsay, or worse.
 

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Thanks for posting this question. Nearly every used boat advertisement boasts "no blisters". ..as if it really means something. While I dont have any personal experience, I can tell you about a friend's experience:

He left his brand new un-bottom painted powerboat in the water for several months. When he pulled it out, he noticed that the hull "had blistered" This was several years ago. He still owns and uses the boat regularly. ...though he doesnt leave it in the water for months on end anymore. His assessment is "its just cosmetic".

So if I was dropping big bucks on a boat, I'd want an unblistered hull. But if I was buying an old cheapee, I wouldnt be concerned. In fact, that might be the key to getting a real steal on a used boat.
 

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Boat pox? No, I don't think it is so serious, as others noted. All blisters are all repairable, even the serious ones (although they are a lot more trouble). Even better, most blisters don't need drastic measures to remedy as other noted previously. Dig out the compromised material, let the divots dry over the Winter, fill with a good epoxy-based material (e.g. thickened epoxy) and fair them, then protect the hull with a good epoxy barrier coat such as Interlux Interprotect 2000E or equivalent.

So long as the barrier coat is not compromised by grounding or collision with something underwater like a deadhead, no more problems. That worked for my '84 and many other boats of the era.

Regards,

Tom
 

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Big issue is not that they destroy your boat but are very expensive to pay someone else to fix. Some boats like certain years of the Valiant it will be a reoccurring issue due to the flame retardant resin used. Others a grinding and barrier coat and you are better than ever.

If you like the boat and can do the work yourself go for it.

Sent from my ADR6425LVW using Tapatalk
 

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This is just my 2 cents. A couple of years ago we pulled 4 soggy layers of blistered fiberglass off a friends hull. The bill for materials only was about 16K. You find many so called experts who say it isn't a problem but it is or will be, I have seen boats in the yard with sections of the hull split straight as an arrow up the main bulkhead seam. If done incorrectly patching blisters is like trying to paint over wood rot and saying its fixed. There are too many good boats out there why buy a rotting hunk of $hit.
 

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4 soggy layers of blistered fiberglass? What kind of boat was that? My experience with blisters has been the same as other posters - kind of a pain, but not really serious. Unless you pay somebody else to fix them.
 

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This is just my 2 cents. A couple of years ago we pulled 4 soggy layers of blistered fiberglass off a friends hull. The bill for materials only was about 16K. You find many so called experts who say it isn't a problem but it is or will be, I have seen boats in the yard with sections of the hull split straight as an arrow up the main bulkhead seam. If done incorrectly patching blisters is like trying to paint over wood rot and saying its fixed. There are too many good boats out there why buy a rotting hunk of $hit.
In 2986 surveys I have seen two boats so compromised by hydrolytic blisters that the hull integrity was degraded enough to be a safety issue. The vast majority I have seen have been cosmetic in nature. I have written my opinion in length on this topic in Osmosis Testing
 

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Sea Sprite 23 #110 (20)
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This is just my 2 cents. A couple of years ago we pulled 4 soggy layers of blistered fiberglass off a friends hull. The bill for materials only was about 16K. You find many so called experts who say it isn't a problem but it is or will be, I have seen boats in the yard with sections of the hull split straight as an arrow up the main bulkhead seam. If done incorrectly patching blisters is like trying to paint over wood rot and saying its fixed. There are too many good boats out there why buy a rotting hunk of $hit.
please believe him.. it makes the boats with a couple of blisters -much- cheaper for the rest of us who can do the work ourselves
 

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Closet Powerboater
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Discussion Starter #11
People talk of doing the work themselves (which is harder to do these days with yards not allowing you to touch the bottom of the boat for environmental reasons), but are they doing the work to fix the cosmesis or are they doing it for fear that the blisters will cause a real problem of some kind.

Much of the advice is "they're not a big deal if you deal with them" but the surveyor types say they've never seen a structural problem, or it's vanishingly rare. So.... does one really have to "deal with them" or is it more like peeling paint on the topsides than anything else?

MedSailor
 

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People talk of doing the work themselves (which is harder to do these days with yards not allowing you to touch the bottom of the boat for environmental reasons), but are they doing the work to fix the cosmesis or are they doing it for fear that the blisters will cause a real problem of some kind.

Much of the advice is "they're not a big deal if you deal with them" but the surveyor types say they've never seen a structural problem, or it's vanishingly rare. So.... does one really have to "deal with them" or is it more like peeling paint on the topsides than anything else?

MedSailor
In the vast majority of cases I believe it's ok to live with it. Just be sure you know what you're looking at ... in the gelcoat only, no problem. If they have gone into the skinout mat you should monitor a little more closely.

Blisters are wildly unpredictable. My own boat was blister free for about 25yrs and then developed a heavy rash of them over one season. I stripped the bottom, put her in heated storage with heat lamps for about five months then applied 8 coats of epoxy. Five years later the epoxy blistered. I should have just left her alone.
 

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While it may not be much of deal on a solid hull ?

On cored hulls at least how Jboats builds them there is at most <1/8" of glass on the outer skin

I have samples from one of my J24s and a J160 that fell over and landed on the open bases of some jack stands and again there is not a whole lot of extra glass :)


I do know some people on freshwater lakes in Texas with boats that spends long amounts of time in VERY hot water and they seem to have more problems ?
 

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While it may not be much of deal on a solid hull ?

On cored hulls at least how Jboats builds them there is at most <1/8" of glass on the outer skin

I have samples from one of my J24s and a J160 that fell over and landed on the open bases of some jack stands and again there is not a whole lot of extra glass :)


I do know some people on freshwater lakes in Texas with boats that spends long amounts of time in VERY hot water and they seem to have more problems ?
My experience with J-boats suggests they should be considered as "disposable boats". I agree balsa cored bottoms are a different kettle of fish.
 

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I do know some people on freshwater lakes in Texas with boats that spends long amounts of time in VERY hot water and they seem to have more problems ?
It is well documented in the litterature that blisters devlopemnt increase with
a) fresh water
b) temp
c) time spent in water.

From this one could also conclude that
swimming pools made in GRP is a bad idea, and eg
a little fresh water inside the boat is not as innocent as one may think, and
integral water tanks made in grp is not a good idea either.

J
 

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It is well documented in the litterature that blisters devlopemnt increase with
a) fresh water
b) temp
c) time spent in water.

From this one could also conclude that
swimming pools made in GRP is a bad idea, and eg
a little fresh water inside the boat is not as innocent as one may think, and
integral water tanks made in grp is not a good idea either.

J
Agreed ... fresh water, warm water and moving water have been long known to exacerbate the problem. I kept my boat in a tight mouth,small, fresh water bay that was also the outflow for the cooling water from an electrical generating plant ... fresh, warm and moving 24hrs a day. I saw more blisters in that harbour than I've ever seen anywhere else.
 

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The fabulous original workmanship :( NOT in this ONE section of the hull that i would guess was done after it was pulled from the mold ?



Thats one of the tiny ones



A tom custom tube remover



with absolutely no issues in the rest of the layup





The original aliment job of the strut/tube/motor was so screwed it was just as well anyway as NOW everything is correct
 
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