Blisters

Hello all. 1981 GB 36. Hauled yesterday for survey. Multiple blisters ranging in size from 1" to 4". Surveyor believes that the larger ones are into the glass.
Thoughts....... View attachment 1

Most 40 year old Taiwan boats have at least a few. It wouldn't be a deal killer for me. Grind out the bigger blisters and fill, wouldn't worry so much about the smaller ones. Try and negotiate a discount from seller??

Interlux has good information on repairing blisters.

A couple of 1” blisters on a 40 year old boat wouldn’t bother me. 4” blisters do bother me. At this point you need to decide if this boat is special or if the price is special. If not then either require the seller to repair or walk. I am inclined to walk as the boat will develop more of these big blisters over time.

If the boat or the price is special then you can either ask that the seller repair or negotiate a better price. Blister repair is expensive, not the repair work but all the yard fees that add up while waiting for things to dry. Just remember, some day you will be the seller on this boat. You want to be in the boat so cheap that you won’t feel troubled if you practically give it away later.

It’s always hard to do a valuation from photos but that boat looks like it has a lot of 1” blisters.

Blisters are the minor issue most of the time, it's hyrolysis of the laminates that can get complicated.

I ground halfway through my hull in a 6x6 foot area to build back hydrolysis damaged laminates...plus other areas much larger than the largest blisters to get to dry solid glass.

Did your boat spend a lot of time in southern waters?

It's always worth a look to see just how far the damage goes if you care. If like most people that think I am crazy, sure just patch'em up and keep trawlin".

Looks like it`s been repaired previously, so well established in the hull. Repair it and it will likely recur. Grinding them out, ensuring they are dry, repairing with layers of glass mat, and finishing smooth, is a time consuming job. We did it, all over, lovely smooth hull for 6 years, then it came back. Disappointing when you think you nailed it.
We haul out and antifoul here every 12-18 months, making doing a few each time feasible but in USA there seems to be years between a/fs. If you buy it assume you`ll be living with it.

I sold a 1982 boat in 1995. In 93, I saw that it had under 2 dozen 2" to 3" blisters. On my next haulout, I ground to dry laminate, filled with thickened epoxy and covered with bottom paint. Not a fancy fix, dirt cheap and quick enough to do between the end of power washing and the application of bottom paint on a 4 hour lift at the club. At that time I thought I would own that boat long enough to get fancier if necessary.

Before that happened, I bought a trawler and listed that boat. When I sold, the purchaser's surveyor complimented me on the fix, so there was no impact on the price I got.

YMMV

A boat yard owner told me, "blisters never sunk a boat, put your money somewhere else".

It is a mostly cosmetic issue that buyers use to drive a deal down. Some say it occurs more in fresh water than salt.

Would not be an issue for me if everything else was good.

Choices said:

A boat yard owner told me, "blisters never sunk a boat, put your money somewhere else".

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Agree, it's cosmetic issue.

If laminate was showing I did a proper repair. If it was just gel coat I sanded and faired with thickened resin. A very laborious job. I would not do it again.
Fortunately I don't have to, bottom still looks good after a few years.

If you are going to have a yard do the work, get a quote before agreeing on final price.

if you think blisters are always just a cosmetic thing, you haven't done enough research.

Most often they are, but not always and I have posted pictures plenty of times proving that point.

Just thinking cosmetic can also be the ostrich approach to this matter.

psneeld said:

if you think blisters are always just a cosmetic thing, you haven't done enough research.

Most often they are, but not always and I have posted pictures plenty of times proving that point.

Just thinking cosmetic can also be the ostrich approach to this matter.

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I’m going to agree with psneeld.

If I had a boat with 4” blisters I would certainly ground out the wet material and patch it. Maybe problem solved or maybe just kicking the can down the road, doesn't matter if I already own the boat I already own the problem.

Buying some one else’s problem is different. I’d be much more cautious before I buy some one else’s problem.

Maybe others can confirm, but I was told there are two types of blisters. The ones where water penetrates from the outside (outside in) and the second kind (inside out) where the blisters are formed from a chemical reaction in the laminates. If you pop the blister and it has a vinegar smell, it is the inside out type, and is more difficult to repair in the sense it is deeper and will be an ongoing problem. Whereas the water blister problem can be solved with a couple coats of a epoxy barrier coat.
I did a blister repair on my last boat (hardest job I ever did). The blisters were the vinegar smelling type. I ground them out and had to wait about 10 days for them to dry out. Hindsight I would have paid to have the bottom peeled. I see now where the cost of buying a peeler has really dropped. Just a couple things to consider when pricing in the cost of a fix.

psneeld said:

if you think blisters are always just a cosmetic thing, you haven't done enough research....

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Agree. Guys who did mine said occasionally they have to repair from the inside to the outside of the hull, ie right through. That doesn`t sound cosmetic. Nor did the depth of some of mine. Or the width.

FWIW, we bought Sarawana about 15 years ago, with existing osmosis damage. We negotiated a reduction to cover the estimated repair cost, which if memory serves was about $25K.

The boat still has the blisters, to about the same degree as when we bought the boat, we check her each time she is lifted.

Given the above we have no desire to lift, dry and glass the hull. We use her as is and when it comes time to sell I expect some potential buyer will do the same to me as I did to the PO.

One thing though, I will be quite upfront about the osmosis, not like our previous owner who tried every stupid thing in the book to disguise the issue. It was this behaviour that almost caused us to walk away, which in hindsight would have been a pity as Sarawana has been a terrific boat for us.

Andy, unreliable memory is seeing the redoubtable Sarawana, lifted, resembling a reverse dalmatian. Lots of small widespread blisters I think treated with white filler. Fortunately it remained the same for 15 years of happy cruising, hopefully for many more.

Different though to the larger deeper ones affecting Doriana, which did need work.

My Willard 36 had a decent crip of blisters when I purchased 25-years ago. Negotiated a fair credit with the PO and I figured I would pass it along when I sold. I have fixed most of them over the years so bottom is in decent shape.

4-inch blisters does sound extreme so I would definitely get an opinion whether it's more than cosmetic, which is very unlikely but I'd get a professional to weigh in and discuss.

Obviously, I wouldn't hesitate to buy a boat with blisters. But it doesn't mean I'm naive about effect on resale. Some folks get really nervous about blisters so market is skinnier.

Good luck.

Peter

Blisters and hydrolysis need to be looked at 2 different ways... I have fixed boats with both.

When laminates a bad enough and you can strip of a trash can full by hand, and you still want to put that boat in more of a pond, you are very brave or very foolish.

Yes.... boats have been declared unseaworthy or uninsurable because of hydrolysis. They are far and few between but they do escape buyer's ad surveyor's inspections when they think "don't worry, blisters are cosmetic".

From a story and photos by Steve C. D’Antonio

https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Blisters-and-Osmosis.pdf

"From this description, it is clear that the blister is the
final step in the hydrolysis/osmosis problem"

Thank you all for your input. Just got the engine and generator report. It is as I feared. Little yearly maintenance and replacement of older items have stacked up. Waiting on general survey to see if I will proceed with this boat. If there were only one area to focus on..... not sure I want to tackle 2. Still hoping to loop next year, but time is ticking.

Hello old sea dog. Pulled out my GB32 1978 and the Hull was full of blisters we call fiberglass osmosis. Had to dig them out and let them drain for a couple of weeks. Sanded down the hull completely removing all the layers of antifouling down to the gel coat. Filled up all popped blisters with fiberglass and applied two coats of epoxy based primary and then two coats of antifouling. Perfect result. See photos

koliver said:

I sold a 1982 boat in 1995. In 93, I saw that it had under 2 dozen 2" to 3" blisters. On my next haulout, I ground to dry laminate, filled with thickened epoxy and covered with bottom paint. Not a fancy fix, dirt cheap and quick enough to do between the end of power washing and the application of bottom paint on a 4 hour lift at the club. At that time I thought I would own that boat long enough to get fancier if necessary.

Before that happened, I bought a trawler and listed that boat. When I sold, the purchaser's surveyor complimented me on the fix, so there was no impact on the price I got.

YMMV

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so you basically filled the lost material and leveled out.
I am hearing others use of mat as a filler and the return of blisters. Wondering if that is related.

Soo-Valley said:

so you basically filled the lost material and leveled out.
I am hearing others use of mat as a filler and the return of blisters. Wondering if that is related.

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I don't believe epoxy resin is all that compatible with the styrene binder in mat. Might be more of a case of poor adhesion rather than return of blisters.

Mat doesn’t wet out well with epoxy unless the mat it is sewn like in 1708. But epoxy is the resin of choice for blister protection. So I would not use mat in that application.

Chopped strand matt and epoxy work just fine.

Was repairing a glass canoe yesterday with matt and epoxy.

Epoxy doesn't dissolve the binder in matt like styrene so matt might be harder to get to form on curves/corners, but flat....it wets out just fine and adheres just like any other glass.

The trouble with chopped strand matt close to the water is the random fibers are exposed and help wick water through that layer.

It's overuse was because it hides the print of roving between gel (porous) and the roving below.

So no, it's not a great product for outer layers of immersed areas.

From Wests Systems -

Can WEST SYSTEM® Epoxy be used to wet out chopped strand mat? The answer is yes. The fiberglass strand in mat wets out with epoxy, but the binder holding things together does not dissolve. (It does get put into suspension and is sealed in the cured epoxy.) This undissolved binder causes the wet-out mat to remain a bit stiff compared to wet-out with a styrene-based resin. For gently curving or flat projects like cabin soles or plywood decks, mat and epoxy should work fine. The fabric does not wet out perfectly clear with epoxy. Wet-out clarity of mat with epoxy varies somewhat with different suppliers, but none of them wet out as clear as a good 4 oz or 6 oz fiberglass cloth.

Greetings,
Many years ago I was told that there are two kinds of fiberglass material. One is ONLY compatible with polyester resin and is NOT suitable for epoxy resin and the other is compatible with both poly and epoxy resin. I can't remember if this applied to both cloth and mat but cloth, for sure.

RT Firefly said:

Greetings,
Many years ago I was told that there are two kinds of fiberglass material. One is ONLY compatible with polyester resin and is NOT suitable for epoxy resin and the other is compatible with both poly and epoxy resin. I can't remember if this applied to both cloth and mat but cloth, for sure.

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True of chopped strand matt if using on sharp to almost low radius bends because it just won't lay with epoxy. It's not the resin that's an issue.

But for nearly flat surfaces it works fine. All sources I have read says wetting out and adhesion is just fine. Better materials for different cases, but simple general purpose? Just fine.

Here is my work from yesterday with 1oz chopped strand matt. 2 layers outside, 2 layers inside and stronger than original hull. On radiused hull of canoe.

Comodave said:

Interlux has good information on repairing blisters.

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I am a strong advocate of Interlux products, especially their Interprotect 2000e epoxy primer, which I've used for decades with good results, however, I don't buy into their, or anyone else's, theory that "wet" bottoms can be dried, there is no scientific proof this works for long-term blister reoccurrence, but it sells primer I suppose.

More here https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Blistology-Pt-1-PMM-Jul_Aug-06.pdf

Overall, depending on their severity/depth, I'm not sure I'd let this stop the sale, but the devaluation at resale should be taken into account in the selling price now.

Lying Crawfish Inlet, AK

I supervised scores of osmotic blister repairs for over a decade when I managed a yard that specialized in this type of work, we offered a 10 year warranty and never had a payout, because we followed science based on the U of RI study funded by the USCG, that investigated and determined the causes, proper repair and prevention, of osmotic blistering. We used vinyl ester resin and fairing material exclusively for repairs, with Interprotect 2000e as a binder/primer for anti-fouling. You can use epoxy for repairs and many DIYers do because it is easy to mix and has no VOCs, so much more user friendly, but much harder to work with otherwise.

Old Sea Dog said:

Hello all. 1981 GB 36. Hauled yesterday for survey. Multiple blisters ranging in size from 1" to 4". Surveyor believes that the larger ones are into the glass.
Thoughts.......View attachment 130016View attachment 130017View attachment 130018View attachment 1View attachment 130019View attachment 130020

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I bought my 1973 GB36 in Nov 2020. The hull looked good but I was intending to refit the boat so I wanted to bring it back to basics and had it glass bead blasted to expose any problems. Fortunately the boat was (apparently) barrier coated at the factory and was in excellent condition. The point to my rambling is that I might suggest having it glass bead blasted to open up all problems. Make said repairs and then epoxy (barrier) coat the hull. This repairs everything, protects everything and adds resale value to the boat. I did have one oddity. There was what looked like cavitation holes in a band about 3" wide, at the water line from the bow back to about 2-3 feet. I figured this to be some sort of erosion from the bow wave over the years. A little glass repair and some epoxy filler and it is good as new. Good luck.

I don’t think that in 73 they were barrier coating. Probably some PO did it. Lucky you!

RT Firefly said:

Greetings,
Many years ago I was told that there are two kinds of fiberglass material. One is ONLY compatible with polyester resin and is NOT suitable for epoxy resin and the other is compatible with both poly and epoxy resin. I can't remember if this applied to both cloth and mat but cloth, for sure.

Click to expand...

It is my understanding that you can put epoxy over polyester, but not polyester over epoxy. There is polyester and vinyl-ester. I'm told that the vinyl-ester works well with both polyester and epoxy and is lower cost. Apparently the working time with vinyl-ester is very short. Also the binder material in CSM & 1708 doesn't liquefy with epoxy, but does with polyester. This is what I get from the fiberglass guy at the boat yard.