Osmosis treatment

Surely the real question is whether the boat is worth all that expenditure. Unlike 30 years ago when osmosis treatment was flavour of the month, boats that might have osmosis have fallen in value, treatment cost have risen to the point where it is difficult to justify financially no matter how long it may last. Historically treatment might be something like 10 or 15% of the value of the boat and it was almost impossible to sell a boat that had evidence of osmosis. Now the cost might be 30-50% and have little impact on the short term market value. Some operators have been offering guarantees of 5 years or more, but realistically it is impossible to put any reliable figure on life - let alone define what constitutes failure!
 
Well, I think that is really a piece string question. In theory, if you believe water absorption comes from the seawater through the gel coat, then if you remove that porous gel coat allow all the water in the laminate to dry out and then coat in a relatively impervious epoxy coating plus epoxy based Coppercoat, no water should ever get back in and then leach out in blisters. However there is not agreement even among experts that blisters and wet laminates are necessarily the result of water ingress so the laminate could still bleed out under the coating. There is plenty of evidence that treatments can fail, but that could be due to poor preparation, poor application, inferior materials etc. So it is a bit of an act of faith committing to such expense (perhaps mitigated by a guarantee from the contractor), weighing up the benefits against the cost. Hence my suggestion that this is the starting point rather than "how long will it last" when it is clear there is no definitive answer to that simple question.
 
I would not waste the time on getting it sorted, enjoy the sunshine and go sailing. There is no record of any boat dissolving in water due to osmosis and life is short.
 
Seems like you have found the piece of string - but not the end! Suspect not unusual, nor unlucky. Few owners keep their boats long enough to find out how well it lasts and subsequent boat owners tend to just accept what is so doubt you will get any reliable data about failure rates and times. As I suggested earlier some believe that the chemical reaction continues within the laminate and that the primary cause of breakdown is not water absorption through the gel coat. If this is right, he peeling drying and recoating only delays the process.
 
i got my entire hull down to gelcoat during lockdown as naf all else to do , ive put 3 layers of epoxy paint and 2 layers of vinyguard and 2 layers of antifoul would that be enough to guard against osmosis, luckily there was no signs of osmosis.
 
Rhylsailer99 said:
i got my entire hull down to gelcoat during lockdown as naf all else to do , ive put 3 layers of epoxy paint and 2 layers of vinyguard and 2 layers of antifoul would that be enough to guard against osmosis, luckily there was no signs of osmosis.
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All depends on the condition of the gelcoat and the laminate under the gelcoat: you might have greatly reduced the chance of blisters developing, or you might have accelerated the development of incipient blisters by sealing in moisture. Did you get a moisture check on the hull befoire epoxying?

I'm actually personally not too worried about "osmosis" in an old and heavily laid up hull. I bought a boat with maybe 200 very defnite blisters, quickly individually ground out and filled, without any prolonged drying. Something like 12 years later there were maybe 20 new blisters when I sold the boat.
 
jwilson said:
All depends on the condition of the gelcoat and the laminate under the gelcoat: you might have greatly reduced the chance of blisters developing, or you might have accelerated the development of incipient blisters by sealing in moisture. Did you get a moisture check on the hull befoire epoxying?

I'm actually personally not too worried about "osmosis" in an old and heavily laid up hull. I bought a boat with maybe 200 very defnite blisters, quickly individually ground out and filled, without any prolonged drying. Something like 12 years later there were maybe 20 new blisters when I sold the boat.
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I never got a moisture check but the boat has been out of the water since October so i am crossing my fingers and hoping for the best.
 
Rhylsailer99 said:
I never got a moisture check but the boat has been out of the water since October so i am crossing my fingers and hoping for the best.
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Assuming that it is water getting into the hull that causes "osmosis" (opinions occasionally vary but it is definitely true that it never ever happens with GRP that doesn't get wet), then if water molecules take 20 to 30 years to get in they are not going to escape that much in 6 months. I tend to regard time ashore as time the water is under no pressure to get in, rather than much deep drying out happening.

A boat that might get blisters in 15 years if always in the water might be fine for 30 years or more if out for six months year. The other big factors are water temperature and salinity. The warmer the water definitely the faster you get blisters, and freshwater seems worse than salt.
 
jwilson said:
Assuming that it is water getting into the hull that causes "osmosis" (opinions occasionally vary but it is definitely true that it never ever happens with GRP that doesn't get wet), then if water molecules take 20 to 30 years to get in they are not going to escape that much in 6 months. I tend to regard time ashore as time the water is under no pressure to get in, rather than much deep drying out happening.

A boat that might get blisters in 15 years if always in the water might be fine for 30 years or more if out for six months year. The other big factors are water temperature and salinity. The warmer the water definitely the faster you get blisters, and freshwater seems worse than salt.
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The boat was out if the water for about 8 years and only been in for last 18 months and is on a drying mooring not sure if that would help.
 
CalicoJack said:
We had ours done about 7 years ago, and I’ve just found some nasty smelly blisters. Damn! normal or just unlucky?
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I suspect normal. Osmosis treatment used to provide a lot of employment for purveyors of snake oil.

If you're out of the water, I'd grind the blisters out, leave them to air as long as you can, washing regularly with warm water, then fill with an epoxy filler and go sailing. If you're in the water, go sailing first.
 
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