Osmosis...the horror, the horror...or not, as the case may be

Greenheart

Greenheart

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I just read the Yachtsnet page on osmosis. I'd always supposed that osmosis is a fatal scourge of older GRP boats, the only cure to which is epoxy, at huge expense.

This page doesn't exactly wipe that worry away, but it does seem to describe it with an informed perspective. Worth a serious look:

http://www.yachtsnet.co.uk/osmosis.htm
 
dancrane said:
I'd always supposed that osmosis is a fatal scourge of older GRP boats, the only cure to which is epoxy, at huge expense.
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Yeah, scary stories to make people shovel money for "epoxying" , only to have epoxy blister off in ten years or so to be 'repaired' again...

Well, once I've seen a boat with blisters going into the hull laminate proper most of thickness, delaminated in spots big as hand. But guess this was just low quality resin mix,or job sloppily done in those places. Otherwise mostly it's just gelcoat blisters, outer cover failing, nothing is permanent after all. What do you do when surface is weathered with age? Sand, wash, paint, ain't it?.

Buying 40 year old hull I was advised by surveyor she is wet. Really wet.
Topsides acceptable (quite a surprise in Welsh horizontal rains), just below waterline - high reading; but bilges awfully saturated, sure osmosis sign... :eek:
Drying recommended, and a treatment. No idea how could I dry those bilges, happens to be watertank, full at the survey.

So it was soaking for 40 years, from both sides, and with fresh water to make it even worse. Still there, nevertheless :cool:

Just a thought: people worry about some blisters on bottom that can be easily faired and painted over should one care, no-one will see anyway - but go buying cored decks, sometime even with teak screwed into... :confused:
 
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Last year I had 30 years of antifoul blasted off, great job but then told I had osmosis and gel peeling suggested at about 6K, nearly 25% of the value of the boat, after taking lots of advice the local painter at the yard suggested sand, fill, prime and antifoul for £600, huge difference, everyone admires the bottom when ashore and no one can see when afloat, a pragmatic solution for a 33 year old boat built like a tank!
 
Dancrane, many thanks for posting that. It's very interesting, isn't it. I can say that it has certainly helped me towards a decision on my own boat after I have the hull blasted.
 
SeamanStaines said:
Does anyone know of a boat actually sinking because of osmosis? As I see it it just ends up a tad heavier!
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The "tad" is tiny and not really measurable. There are pictures on the web of hulls damaged due to Osmosis/Hydrolosis such that structural integrity will likely have been lost. I own a so called MAB and looked into this subject and I concluded that for the majority of older boats it's not likely to be such a big issue. Indeed, I would not want an old yacht that had the GRP planed back as part of an Osmosis cure.
 
SeamanStaines said:
Does anyone know of a boat actually sinking because of osmosis? As I see it it just ends up a tad heavier!
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No boat experience, but my late mother's GRP loft water tank started a slow leak. Goodness knows how long it had been dripping before we spotted the wet patch on the ceiling; mould suggested it might have been a while. And the tank was decades old and no doubt predated any knowledge of "osmosis". A quick Google shows it's quite an industry...

Mike.
 
BlowingOldBoots said:
I would not want an old yacht that had the GRP planed back as part of an Osmosis cure.
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This is what I found particularly interesting in the Yachtsnet article...the suggestion that the cure may be more damaging than the problem...

...unhappy news if one has lately shelled out a quarter of the vessel's value on epoxying.

The idea of epoxy forming a seal that is proof against ingress of water, is very appealing...so, hearing that water molecules are small enough to invade their way through any coating/finish, is a worry...

...then again, the periodical low-tech response to local blistering sounds like a practical, not-very-irksome strategy.
 
Makes for happy reading compared to other tales of woe. Of course, steel, ali, ferro and wood enthusiasts will not be so positive.
 
(Sorry Mogy, this doesn't relate to your question)

A pal of mine is a car-nut, knows little of boats...he asked me the other day, how does the lifespan of GRP boats compare with the age of cars?

He meant, how long till a plastic boat, even if cared for, reaches the end of its intended/expected lifespan, like an E-class diesel with 300,000 miles on the clock.

I only said that we don't really know - because many early GRP boats are still going strong, so there's no inevitable decline. That may relate to the cautiously heavy lay-up of early glassfibre boats, but in principle GRP is massively tough stuff. I hope I was right?
 
dancrane said:
(Sorry Mogy, this doesn't relate to your question)

A pal of mine is a car-nut, knows little of boats...he asked me the other day, how does the lifespan of GRP boats compare with the age of cars?

He meant, how long till a plastic boat, even if cared for, reaches the end of its intended/expected lifespan, like an E-class diesel with 300,000 miles on the clock.

I only said that we don't really know - because many early GRP boats are still going strong, so there's no inevitable decline. That may relate to the cautiously heavy lay-up of early glassfibre boats, but in principle GRP is massively tough stuff. I hope I was right?
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Occassinoaly quite by chance you may stubble across a little huddle of grp yachts gradually merging with the greenery in some backwater boatyard.The only way to make them disappear is to burn them or cut them in little bits and land fill.....Considering how may must have been moulded its quite strange that they hide so easily...
 
mogy said:
Occassinoaly quite by chance you may stubble across a little huddle of grp yachts gradually merging with the greenery in some backwater boatyard.The only way to make them disappear is to burn them or cut them in little bits and land fill.....Considering how may must have been moulded its quite strange that they hide so easily...
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Maybe old hulls can be dropped into a vast 'chipper', to come out as a constituent element of road-building aggregate which won't need excavation? Maybe. :rolleyes:
 
I remember getting the survey done, quite a few patches of minor osmosis found, hull is 32yrs old though so no suprises.
Surveyor says it won't get better, to keep an eye on it whenever the boat is lifted out for routine stuff. Said it could be a problem in about 25 years.

By which time I will be six foot under and beyond caring.

As for selling on, I will be her last owner I think. When I am done with her it'll be off to the mincer.
 
dancrane said:
I just read the Yachtsnet page on osmosis. I'd always supposed that osmosis is a fatal scourge of older GRP boats, the only cure to which is epoxy, at huge expense.

This page doesn't exactly wipe that worry away, but it does seem to describe it with an informed perspective. Worth a serious look:

http://www.yachtsnet.co.uk/osmosis.htm
Click to expand...

Is it conceivable that the whole yachting industry saw the Osmosis fenomena as a money making scam and only now that boats are STILL floating and owners are still sailing that they have decided to come clean and admit that Osmosis was not such a killer......
 
mogy said:
Is it conceivable that the whole yachting industry saw the Osmosis fenomena as a money making scam and only now that boats are STILL floating and owners are still sailing that they have decided to come clean and admit that Osmosis was not such a killer......
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A bit like the "Y2K" computer problem 13 years ago, back when I was still in the IT industry...

Mike.
 
mogy said:
Is it conceivable that the whole yachting industry saw the Osmosis fenomena as a money making scam and only now that boats are STILL floating and owners are still sailing that they have decided to come clean and admit that Osmosis was not such a killer......
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First part of sentence: yes indeedy. Second part: they knew that from the start. We bought a 13 year old 28 ft AWB in 2001. When she was lifted for survey I spotted the blisters, and the surveyor and broker agreed they needed attention. We got £3k off the price (based on a quote from a specialist company), spent £1k having it fixed by a very competent one man band, and sold the boat two years later for the price she was originally offered before we bought her.
 
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