Hull blisters... on a 1964 boat?

[starsoup]

Irredentist hull blisters refusing surrender on early glass hull.



Personal background: longtime dingy racer looking at first "big(ger) boat" purchase. Have read extensively on late 70s to early 80s blistering - or what I'm likely to encounter with certain older, lower price point boats - and generally narrated as the manufacturer's search for less expensive chemical compounds subsequent to oil shock of the time. Resolution (I believe, by way of common consensus) is to grind off original gel coat completely, barrier coat and re-gel coat. Pass on any boat so effected unless the selling price anticipates this repair.



But haven't heard of the condition as manufacturing issue on earlier boats. Present owner believes this is indeed the case.



He's had the boat for 10 years or so. And the owner before him for at least as long. When present owner first bought the boat, it was covered with blisters below the waterline, his description was "everywhere". He ground these out, re-glassed and painted. And this repair appears to have held. He did the same repair to less extensive blistering above the waterline last year and it came out great. But within 6 months, extensive large blisters returned with several now "popped", palm sized sections of paint missing. Owner is competent, long time boater, did his research before the repair and was advised by local professionals. And he describes similar, unsuccessful attempts by the previous owner. As best as he can conclude, the original glass must have some unsuccessful mix. It's a 38' hull, he didn't grind off the original gel coat entirely. He treated his repair in sections, grinding these down, applying barrier coat and repainting. The recurrent surface defects are blistering and what he describes as a weird gel coat-like crazing in the paint where there is no crazing present below in the gel coat proper.



Interested to hear if owners of first generation fiberglass boats have encountered persistent blistering and what may be the cause when it appears to be characteristic of the entire hull.



cheers.

[SailingHarmonie]

As you are learning, "blistering" is a good deal more complex a topic than the usual story from the armchair sailor crowd. You can tell somebody doesn't know about blistering if they tell you WHY without looking or asking questions. Most people (including professionals) just repeat whatever story they heard. The chemistry is way more complicated.

If there is blistering above the water line you can safely say it is NOT an osmotic effect, but an intrinsic property of the aging lamination. New gel and/or barrier coat seems unlikely to help.

I think you will find--despite the pronouncements to the contrary--not all fiberglass hulls are forever.

[Bowdrie]

Originally Posted by SailingHarmonie

As you are learning, "blistering" is a good deal more complex a topic than the usual story from the armchair sailor crowd.

True enough.
Research has shown that the causes are myriad.
We have learned that proper climate control during the laminating/lay-up process begets a higher quality product.
Keeping the mat/cloth/roving in a clean and DRY environment before use is important too.

[starsoup]

Originally Posted by SailingHarmonie

If there is blistering above the water line you can safely say it is NOT an osmotic effect, but an intrinsic property of the aging lamination. New gel and/or barrier coat seems unlikely to help.

Interesting. So you'd surmise (as the present owner has via default, that past remediation hasn't worked) that the issue originates from time of manufacture? Some chemical conflict within layup of hull itself, breaking down, emitting gas - whatever - over time, making surface enclosure like gel coat impossible.

For any following along this is the best rundown on the question I've read:
https://www.passagemaker.com/technic...per-evaluation

Moisture meter is a waste of time unless boat has been out of water long enough to dry out.

And then several spots need to be taken down to glass and that visually inspected.

If it's dark and clear, it's ok. The moisture at fault is between glass and gel coat. (That remediation is ONLY stripping the gel coat, barrier coating and repainting.)
If it's returning to white, that indicates separation of resin from laminate within the glass itself. And the question is how many layers are so effected.

In the mildest cases, the moisture might be just beneath the gelcoat at the first layer of fiberglass material. In a moderate case, the moisture might be between the first and second, or second and third layers of fiberglass.

In the more severe cases, the moisture might have worked its way all the way into the structural laminates, perhaps 1/8 inch deep or more. In order to make an informed buying decision, you must know the answer to this question.

A healthy laminate will be dark and somewhat clear. If the laminate is milky with yellowing and/or whiteness, moisture has found its way in. Invariably a milky laminate will also ping the moisture meter. This cloudy laminate, referred to as “hydrolyzed,” speaks to the crux of the blister issue.

All is lost. Give up. Only a fool entertains hope.


Tough situation when someone wants to sell their boat. And get it out of dry storage and onto their mooring. Simply no way for prospective buyer to understand how much needs to be cut out.

[Jim Cate]

Considering the number of similarly aged boats available, it seems quite unwise to pursue this one. Such pervasive laminate issues will not be easy to solve and perhaps are not solvable. You are risking a long term problem with no clear ending.

I would seek another vessel.

Jim

[Scrimshaw4]

Older hulls, pre-approx. 1998, were made with polyester resin. This is a linked molecule product that allows moisture to migrate across it. Failed / old barrier coats actually allowed moisture to weep through and subsequently penetrate the gelcoat where it then was captured by the polyester resin. The moisture then spread traveling from molecule to molecule allowing room for more moisture to be absorbed..
Around 1998 builders switched over to vynlester resin, a non-linked molecule. When moisture penetrated it tended not to migrate. Problems have been found with barrier coat products like Interlux 2000e after about 5-7 years. They tend to brake down and some say start to trap moisture against the gelcoat.

A heavily blistered hull probably should be peeled, reglassed, faired, gelcoated, 2 part epoxy barrier coated and then bottom painted. (I prefer the Sherwin-Williams barrier coat.) The process can be expensive but that's up to the owner to decide if it's worth it. JMHO

[GILow]

Originally Posted by Bowdrie

True enough.

Research has shown that the causes are myriad.

We have learned that proper climate control during the laminating/lay-up process begets a higher quality product.

Keeping the mat/cloth/roving in a clean and DRY environment before use is important too.

Even these rules are far from reliable. The yard where the Swansons were built was notoriously dusty, humid and full of salt laden air. And yet, osmosis in Swanson yachts is a rare and trivial issue.

I don't think there really are any hard and fast rules. Guidelines perhaps.

At the end of the day, one of GOOD things about buying old boats like these is that their reputations are well established in terms of osmosis and structural issues, so it's easier to avoid the lemons.

[boatpoker]

Originally Posted by Scrimshaw4

Older hulls, pre-approx. 1998, were made with polyester resin. This is a linked molecule product that allows moisture to migrate across it. Failed / old barrier coats actually allowed moisture to weep through and subsequently penetrate the gelcoat where it then was captured by the polyester resin. The moisture then spread traveling from molecule to molecule allowing room for more moisture to be absorbed..
Around 1998 builders switched over to vynlester resin, a non-linked molecule. JMHO

The Issue was orthopthalic versus Isopthalic polyester resin (easily researched). Isopthalic polyester resin is still used in the vast majority of fiberglass boats built today. You are misguided in your understanding of cross linking in polyester resin.

Some manufacturers do put a vinylester gelcoat on their polyester boats and even fewer put a vinylester skinout mat but no production boat builder builds a hull solely out of vinylester.