OSMOSIS - Do all boats get it? Or just a few?

[mrk123]

Looking for a boat, 80s, 90s 30ft+.

Some have serious osmosis, some have slight.

Is it really something to worry about? Do all fibreglass / GRP boat hulls get it eventually or are some boats built better than others?

[Rumrace]

Polyester is not water proof. Vinylester is.
Blisters are cause by water travelling inside the glass. A few hulls claim to be solid Epoxy but they are not. My boat has two layers of Vinylester which gives the boats a nice durable shine. One layer of roving is Kevlar and Kevlar banding added in key stress points.
Catalina caught up to competitor Jeanneau in 1994 by adding a single Vinylester skin. There would be a dramatic difference between and future osmosis on future Catalina’s Now to get a blister the hull needs to be damaged.
The real cure for a blistered hull I’m sure you know is to sell it.

[boatman61]

To the best of my knowledge no boat has ever sunk because of osmosis, slowed down hull speed yes, but sunk.. No.

[bil56]

" no boat has ever sunk because of osmosis"
never sunk, ok, but less rigid hull, distended rigging to be taken up often, soft bottom and risk of significant damage to the bottom in the event of grounding on the keel

[rslifkin]

Even with all-polyester hulls, it depends. If it's got an epoxy barrier coat applied early in life, it'll probably never blister unless something gets damaged. But even without a barrier coat, some hulls are prone to blisters, others rarely blister. All depends on the exact resins used, the hull layup, etc.

[maine50]

I have a Tartan 41 built in 1974. Still no blisters.

[boatman61]

Originally Posted by bil56

" no boat has ever sunk because of osmosis"
never sunk, ok, but less rigid hull, distended rigging to be taken up often, soft bottom and risk of significant damage to the bottom in the event of grounding on the keel

I think more hulls are damaged by over tight rigging than osmosis.. I am just going on a dispute with an insurance company about hull coverage on a boat with 'early signs' of osmosis.
They were reluctant to issue cover, I made the argument and they accepted it and gave me the cover.
Hull rigidity to my mind depends more on internal bulkheads, stringers etc than a lumpy bottom.
Osmosis is an American paranoia, in Oriental the yards main work came from boat Hull peeling..

[Rumrace]

Take care of your bottom mother said or you’ll get blisters

[Bowdrie]

Originally Posted by mrk123

Looking for a boat, 80s, 90s 30ft+.
Some have serious osmosis, some have slight.
Is it really something to worry about? Do all fibreglass / GRP boat hulls get it eventually or are some boats built better than others?

The Clean Air Acts of '63 and '70 instigated the process of severely limiting the amount of VOCs that various chemical compounds could contain.
Polyester resin contained copious amounts of Styrene, (a bad VOC).
The billions of fibers in fiberglass mat were held together with a "sizing" that would dissolve in the presence of Styrene, this allowed the fibers to "wet out".
When the new "Low(er) VOC" resins were first introduced, they did not totally wet-out the mat, leaving microscopic "pathways" that moisture could travel along.
Cloth and Roving had little issue, they have little sizing, (mostly as an anti-static measure,) but if you hold them up to light you can see that they have a lot of "open space", kind of like a tea strainer.
Gelcoat, with its large solids content is, (or can be,) rather impervious to moisture penetration, more so than plain resin.
As problems with blisters began to surface two things became apparent.
1, The sizing in the mat was preventing total wet-out.
2, The main cause of blistering was the vapor pressure of water/moisture/humidity INSIDE the hull forcing its way to the outside surface where it accumulated under the gelcoat.
For the years of boats you're looking at, little worry.
The fiberglass and resin companies fairly quickly reformulated their products to insure complete wet-out.
There were some real serious problems with Uniflite boats, they used a fire-retardant resin, "Hetron" that exacerbated the problems.
The newer stuff is better, and the "bad" stuff was fairly short-lived, and even with the bad stuff the problems had much to do with the initial care and quality of the lay-up schedule, lots of roving and cloth=good, too much mat=not so good.

[fstbttms]

Originally Posted by mrk123

Do all fibreglass / GRP boat hulls get it eventually...?

Speaking as a professional hull cleaner with almost 28 years (and many, many thousands of boats) experience, I can say that the majority of boats do NOT get blisters.

[Rumrace]

Bowdrie that was a perfect explanation.

It’s also why Jenneau went back to hand laid and why Lurs and Hatteras had some serious de lamination. I saw serious chunks come out of Mainship and Cheolee.

It’s also why I firmly believe we are about to see our yachts 3D printed. Hanse printed Yacht has some serious ability to not only assure each molecule is attached carbon fibre or polycarbonate connects can be made in long strands circling the entire hull @.05 mm accuracy. Hanse with a dual head machine CnC the surface leaving a perfect Vinylester surface better than cast.
Several smaller boats have started production and the current 3D printer at Hanse could print up to a 55’ boat.
Polyester gel can not be exposed to oxygen curing. Topical gel coat pushes a wax to the surface to prevent it from being exposed to air. In a mould the wax is just release was and there is no wax in this gel coat.
It’s feasible and likely we will see hulls and couch roofs being printed in printed moulds.
Until then if your hull was not made with an 80,000$ a year QC person it’s good chance it has a void some place. Some manufactures were never told the interior gel coat is as important as the exterior.
Some buried chopper gun and foam filler.
Each boat has some silly flaw to watch.
Best defence I think is repair instantly. Coach roof or hull get on it. There is a 1965 SeaRay up north owned by the natives at Casino Rama. Has a beater outboard. Being a tribe possession everyone uses it. Has one bad patch on the port gunnel otherwise clean. They never bottom paint it. Just wax. I saw the hull on its log cradle it’s mint!
I have an 86 Donzi hull a couple dock cracks two blisters and likely from beaching the hull. Some folk did exceptional work for a period.

[mrk123]

Originally Posted by fstbttms

Speaking as a professional hull cleaner with almost 28 years (and many, many thousands of boats) experience, I can say that the majority of boats do NOT get blisters.

No, but if a boat is listed as with osmosis, it's a cause for concern yes?

[Rumrace]

Yes a boat listed with blisters is likely a heart breaker. Like the pros here said it doesn’t have to happen to any brand but it can. They all have a few skeletons in the closet and there are some truly garbage boats never intended for a long life.

[rslifkin]

Originally Posted by Rumrace

Yes a boat listed with blisters is likely a heart breaker. Like the pros here said it doesn’t have to happen to any brand but it can. They all have a few skeletons in the closet and there are some truly garbage boats never intended for a long life.

And then there are boats that are a little bit cheaply built, but will last fine with good care. But many of those were sold for a low price, so they've had bad owners and have been allowed to go to crap over time.

[Rumrace]

About 16-18 years ago some dealer was trying to unload a Bayliner 40’ Express Cruiser. Was a good looking boat, at a distance. He showed it at the Winter Toronto boat Show, The Orillia in the Water Boat show. No boaters were going for a tour just people at the show or prospective boaters I guess. Some guy in a massive cottage bought it. We could see the roving through the blue stripes. The gel coat was not consistent and we all knew 60% of the hulls structure above the water was chopper gun and foam. It why a guy with too much money bought the boat.
The cottager hit a rock up near the top of the lake. Was at peer 11 being repaired. The cottager got a much smaller more expensive Cobia and the Bayliner slipped from memory.
Fast forward a business associate calls me at tells me one of our clients has bought a boat and he wants me to teach him how to drive it. Sounds fun so I meet the new owner at Ontario place to give him lessons. Damn if he didn’t buy that cursed 40 Bayliner “ dirt cheap” he pointed out. Lake Ontario had good rollers on. 4 adults 2 big trim tabs 2 454’s and the boat handled like light weight junk. It’s delaminated by now and will never ever be missed. The owner died from unrelated heart disease so I will not speak ill of his unfortunate purchasing thinking. Not to say Bayliner didn’t make great boats. I know several 32 Contessa’s going strong with clean hulls. I don’t know where Bayliner popped the 40 out but their crew did crap work.
A decent surveyor with the right equipment will sound the hull. Some just charge for insurance sake with a long list of their experiences. This is the “Noah “ surveyor more concerned about their history than your boat. Frankly the best kind for a pox boat cause he will scare you with stories.
The “Scientist” surveyor will know ever pressure every hard point Mount every bearings age the likely condition of the engine and forecasting long term budget for restorations.
Surveyors often already know the boats in your area. If not they have seen sister ships 100 times.
A good one is a great investment.