Blisters

[ronobrien]

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

I am only the 3rd owner. The first owner had it 1973-2000. It had to be him as the most recent owner (2000-2020) knew noting about it. The guy that blasted the hull warned me beforehand about what might happen (CYA). When he was done he said he hadn't ever seen a hull it that good of condition. So, yes, lucky me. Thanks.

 

[psneeld]

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.

True that the binder doesn't dissolve but that doesn't matter. It wets out and sticks just fine.

 

[RickyD]

I bought a 1974 sail boat with a blister or more in every sq ft. We, me and my partner, ground off the gel coat, bagged the hull in plastic and added two AC units to keep the air inside dry, dried the hull from Feb 1 till the end of April. We then used West System Epoxy thickened with micro balloons to fill and fair the divots with a couple of applications. Then it was six coats of their epoxy. We could get on two coats a day. Then next work day started with light sanding, then two more coats. It held up for 12 years. Then every hall out we would have a blister or two maybe three. I would treat them individually. I sold the boat after 20 years of fun and yes the survey haul out showed a couple blisters, no big deal.

 

[psneeld]

Here is one opinion that I found agrees with many "experienced yards" and "glass experts" in and out of the boat business... and especially for those that think blisters (etc) are only cosmetic.

"In real life, we are starting to see failures in hull bottoms we think are directly related to
hydrolysis damage to laminate resin. In six separate cases, we have seen serious, though
the hull fractures at the keel roots on fin keeled sail boats. In each case, the laminate resin
was severely hydrolyzed. We have seen two cases of laminate fracture across bulkhead
hard spots in two powerboats which we thought were related to hydrolysis of the laminate
resin. The good news is that eight boats is not a lot of boats, but consider that these are
only the ones that we have seen. Surely there are more out there and surely there have
been boats lost for these reasons as well. Accident investigation on sunk boats is not like
aircraft crash investigation. Unless the boat is in the way, it is usually not raised and the
cause of sinking investigated.
We can suppose a lot from these tests and experiences, but we still cannot establish
specific strength data for an individual boat in the field. Suffice it to say that hydrolysis
weakens the bottom and we are seeing failures. This alone should be sufficient reason to
undertake repairs to hydrolyzed laminates as preventative maintenance as soon as
possible."

https://fiberglassatlanta.com/webdocs/blisters.pdf

 

[bogranjac1]

T.F. is a great site ?
You can quickly learn about everything Not wanted to be seen in a boat.?

 

[SoWhat]

Here is one opinion that I found agrees with many "experienced yards" and "glass experts" in and out of the boat business... and especially for those that think blisters (etc) are only cosmetic.

An "opinion" by someone in the blister repair business who bases his opinion on a 35 year old study by two individuals. It reads more like a sales pitch for his business.

Blisters are cosmetic whether or not caused by hydrolysis or poor lamination.

No boat has ever sunk from blisters.

 

[psneeld]

No .... not from blisters but which may or may not be a symptom of hydrolysis which could weaken a hull enough to sink it.

Fixing blisters without further inspection may be getting rid of one syptom but ignoring the disease.

The amount of info on the whole web is lacking ....but after finding hydrolyzed laminates in a 6 foot by 6 foot area of my hull under a fuel tank that was deeper than 1/2 way through the hull, I spent the better part of a year researching hydrolysis. It included visits to glass repaid guts and dozens of phone calls to yards that were experienced in this work.

The consistency of info at the top of the pyramid seems consistent with experience, not what I see in forums.

There is no way to prove whether a boat has or has not ever sunk from blisters, but I would think it rare. Hull cracks from hydrolysis damage.... much more likely a possibility.

 

[Steve DAntonio]

An "opinion" by someone in the blister repair business who bases his opinion on a 35 year old study by two individuals. It reads more like a sales pitch for his business.

Blisters are cosmetic whether or not caused by hydrolysis or poor lamination.

No boat has ever sunk from blisters.

I don't disagree that the author has a dog in the fight, and thus might be deemed biased, however, the decades old U or RI Rockett study remains seminal in the industry, nothing substantive within that report that I am aware of has been refuted.

The "tight" and "loose" gelcoat comments are a bit fast and loose and that theory is not widely accepted anywhere I'm aware of, and it's not contained in the study.

Most osmotic blisters are cosmetic, however, if deep enough and large enough, and if enough fiber whiting occurs/resin corrosion, osmosis can be structural.

Lying Little Port Walter, Baranof Island, AK

 

[SoWhat]

I don't disagree that the author has a dog in the fight, and thus might be deemed biased, however, the decades old U or RI Rockett study remains seminal in the industry, nothing substantive within that report that I am aware of has been refuted

The URI study was seminal in it's day but is very outdated. It was done at a time when Chinese/Taiwanese builders were changing resins and catalysts frequently. Gel coats were clearly more porous. Lamination quality was highly dependent upon the large swings in temperature and humidity. Gel coats, resins, and application techniques have changed considerably since 1986.

Most osmotic blisters are cosmetic, however, if deep enough and large enough, and if enough fiber whiting occurs/resin corrosion, osmosis can be structural.

Yes, per the URI 2000 report severe blistering that goes the hull could be structural but it is rare. Common surface blisters are not structural and can be easily repaired using polyester resin, chopped glass, and colloidal silica or alternatively the commonly used epoxy resin. Deeper blisters extending into the laminate (but not completely through) are also easily repaired but require a bit of expertise to determine how deep to go.

It is my opinion that both surface and deep blisters are cosmetic and easily repairable but if the number of blisters is in the hundreds or severe then I would be thinking about a bottom peel or a fire sale.

..

 

[psneeld]

It didn't take long to figure out the worth of much of the advice on the net. Nothing like actual hands on experience and in depth research to find out what you need to know. A lot of them there Taiwan boats still in use and being resold everyday. This is about them, not newer or different build boats.

 

[Old Sea Dog]

That right there causes concern.

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