Is Osmosis Treatment More Like An Appendectomy Or A Prison Sentence?

[Simon F]

I've been browsing a lot of GRP sailboat listings in the, forty-something year old, twenty-something thousand quid range, looking for a boat which has been well looked after and seems (comparatively) well set up for a couple of decades to come. One thing that strikes me is how many adverts mention major and expensive osmosis treatment in the last 20 years. Maybe a third of them? It got me wondering about the efficacy of such procedures. I can’t think where I would look for figures that would shed light on this and so I’m appealing for a straw poll.

It seems to me that amid the heady optimism around the millennium a person with a twenty year old, forty grand yacht might very likely have viewed a few grand to peel and re-epoxy its pimply hull as a prudent measure to preserve their investment, but, fast forward a whole generation, (or, seven prime ministers in old money) and a lot of inflation in the epoxy market later and by the time it ends up in my hands, 10+ thousand pounds seems a disproportionate outlay to shell out on a 20k 45y/o bargain basement boat. Hence my question. If osmosis treatments are as effective a fix as having your appendix out, It would probably pay me to limit my search to boats that have had already the op. but, on the other hand, maybe the fact that treated boats needed treatment to begin with, marks them out as the kind of recidivist bad-uns who’ll surely re-offend and get banged up for another stretch in chokey?

I appreciate that it depends on a lot of factors - what was done? - why was it done? - when was it done? - was it done by someone who knew why it was being done, whether it had been done before or how to do it?…

None of that matters for the purposes of this discussion. I’m not asking about any individual boat even though that would obviously improve the accuracy of the assessment. The question is- BROADLY, does knowing that a boat around forty years old was treated for osmosis twenty years ago confer a higher or lower chance of problematic osmosis in its future than knowing it hasn’t?

I’m betting lower. I’m hoping lower. People can change. The system works.

 

[KevinV]

Extensive, expensive (and often pointless) osmosis treatment was all the rage, with very varying efficacy - simply preying on fear and ignorance.

I'd give little credence to any work done on a boat 20 (or however many) years ago and simply judge by current condition.

 

[alahol2]

I work on the principal that if a 40 year old boat hasn't got osmosis yet it's highly unlikely it will get it in the next 40.

 

[Simon F]

Extensive, expensive (and often pointless) osmosis treatment was all the rage, with very varying efficacy - simply preying on fear and ignorance.

I'd give little credence to any work done on a boat 20 (or however many) years ago and simply judge by current condition.

Thank you sir. That's exactly the kind of unequivocal answer I need.

 

[Wansworth]

Extensive, expensive (and often pointless) osmosis treatment was all the rage, with very varying efficacy - simply preying on fear and ignorance.

I'd give little credence to any work done on a boat 20 (or however many) years ago and simply judge by current condition.

It’s been mentioned many times in these hallowed forums that does it really matter,no boat has foundered due to osmosis.Knowing that your yacht is sodden with water could be a shame as it’s not perfect but it carries extra weight might improve its sail ability.

 

[Simon F]

I work on the principal that if a 40 year old boat hasn't got osmosis yet it's highly unlikely it will get it in the next 40.

Thanks TW and thanks for your anchorages site too. Very handy.

 

[Tranona]

Just like your teak deck question - assess each boat on its merits as it stands TODAY, not what was done 20 years ago. Your reasoning as to why treatment was carried out is sound. 20+ years ago a 10-20 year old boat with high moisture readings was seriously devalued by the market and the "lost" value could be restored and even enhanced by treatment. Not all treatment was effective so did not prevent future moisture absorption, but probably most were effective. However now probably the most common approach if the moisture has led to blistering is to deal with them by grinding out and filling, or even ignoring them.

In your position I would not reject a boat with blistering. The price asked will usually reflect this and in most cases the long term structural life of the boat is not compromised. You have to accept that almost all boats of that era (pre 1990s) will have in effect inbuilt osmosis because of the materials and processes used. Although you may seem to have a large choice of boats in reality finding one that you like that meets your requirements of providing a sound base for long term ownership without significant future expenditure is a challenge. You are buying the fag end of the boat's economic life.

 

[Simon F]

Just like your teak deck question - assess each boat on its merits as it stands TODAY, not what was done 20 years ago. Your reasoning as to why treatment was carried out is sound. 20+ years ago a 10-20 year old boat with high moisture readings was seriously devalued by the market and the "lost" value could be restored and even enhanced by treatment. Not all treatment was effective so did not prevent future moisture absorption, but probably most were effective. However now probably the most common approach if the moisture has led to blistering is to deal with them by grinding out and filling, or even ignoring them.

In your position I would not reject a boat with blistering. The price asked will usually reflect this and in most cases the long term structural life of the boat is not compromised. You have to accept that almost all boats of that era (pre 1990s) will have in effect inbuilt osmosis because of the materials and processes used. Although you may seem to have a large choice of boats in reality finding one that you like that meets your requirements of providing a sound base for long term ownership without significant future expenditure is a challenge. You are buying the fag end of the boat's economic life.

You're right, it is a challenge. But I've had good results in the past being thorough and patient and realistic and circumspect. It's very helpful having the boat owning fraternity to consult with too.

 

[Stemar]

Extensive, expensive (and often pointless) osmosis treatment was all the rage, with very varying efficacy - simply preying on fear and ignorance.

I'd give little credence to any work done on a boat 20 (or however many) years ago and simply judge by current condition.

I agree. From amateur research done over the years, I'm convinced that a few - or even a lot - of small blisters are nothing more than a good reason to get a price reduction when buying. You can deal with them when the boat's out of the water, or not bother.

Osmosis can be a problem, blisters the size of dinner plates would definitely get my attention, but is this osmosis or delamination due to faulty layup? Whichever, the repair is likely to involve major work.

 

[geem]

I've been browsing a lot of GRP sailboat listings in the, forty-something year old, twenty-something thousand quid range, looking for a boat which has been well looked after and seems (comparatively) well set up for a couple of decades to come. One thing that strikes me is how many adverts mention major and expensive osmosis treatment in the last 20 years. Maybe a third of them? It got me wondering about the efficacy of such procedures. I can’t think where I would look for figures that would shed light on this and so I’m appealing for a straw poll.

It seems to me that amid the heady optimism around the millennium a person with a twenty year old, forty grand yacht might very likely have viewed a few grand to peel and re-epoxy its pimply hull as a prudent measure to preserve their investment, but, fast forward a whole generation, (or, seven prime ministers in old money) and a lot of inflation in the epoxy market later and by the time it ends up in my hands, 10+ thousand pounds seems a disproportionate outlay to shell out on a 20k 45y/o bargain basement boat. Hence my question. If osmosis treatments are as effective a fix as having your appendix out, It would probably pay me to limit my search to boats that have had already the op. but, on the other hand, maybe the fact that treated boats needed treatment to begin with, marks them out as the kind of recidivist bad-uns who’ll surely re-offend and get banged up for another stretch in chokey?

I appreciate that it depends on a lot of factors - what was done? - why was it done? - when was it done? - was it done by someone who knew why it was being done, whether it had been done before or how to do it?…

None of that matters for the purposes of this discussion. I’m not asking about any individual boat even though that would obviously improve the accuracy of the assessment. The question is- BROADLY, does knowing that a boat around forty years old was treated for osmosis twenty years ago confer a higher or lower chance of problematic osmosis in its future than knowing it hasn’t?

I’m betting lower. I’m hoping lower. People can change. The system works.

We have just dealt with the nightmare of osmosis. My boat had osmosis treatment, circa 20 years ago. We have owned her for 13 years and sailed her 42,000nm. We came back to the UK last summer and whilst we were home we opted to deal with osmosis blisters. We needed to do the Coppercoat again but the bumps all over the keel and to a far lesser extent on the hull, suggested it would be a good time to sort the bottom.
A boat that had osmosis treatment 20 years ago may or may not have had a good job. I think ours was probably a poor job. My American boat builder friend calls osmosis treatment "the great osmosis scam".
The difficulty we had was that a failed epoxy treatment needs removing. We couldnt use a gelcoat peeler. We tried, but the epoxy coating was so hard, it could not deal with it. It was at risk of destroying the machine. As a result, we had no choice but to grind off the old epoxy with angle grinders and flap disks. This gets it off OK, but leaves the hull rough. We then waited for the hull to dry out.
What was obvious when you remove the old epoxy coating it how thin it is. Ours was paper thin. There was no way this coating was going to last indefinitely. Think of a boat with 7'2' draft in our case. If you leave a tiny hole in the epoxy, even a pin prick, on the bottom of the keel, the pressure of water trying to get in is pretty high. Even the smallest failure of the epoxy coating will lead to moisture ingress. I think this is what happened to ours.
On advice from my American boat builder friend, he suggested we laminate two layers of 300g cloth onto the hull if you really want to do a proper job.
So, this is what we have just completed.its not a job for the faint hearted. It does mean we have 3mm minimum of epoxy coating on the hull, reinforced with glass. The whole thing is horrendous and expensive. Even though we did a high percentage of the work ourselves, we are still into probably £15k for a 44ft boat. The labout cost from the boatyard to assist has been eye watering.
We are coming to the end of the process. We have another coating of fairing compound going on Thursday, more sanding then hopefully some paintwork at the waterline, then coppercoat.
It will be a rush to get afloat and off south to warmer climes before winter.

.

 

[superheat6k]

So has anyone on here yet found the elusive vessel that has sunk or even is about to sink resultant to osmosis ?

I would suggest this thread needs also a shout out for certain Surveyors who have between them created a complete rip off macro industry offering 'Osmosis repairs'.

Invariably coating an existing water soaked hull (there is a clue here - after all they are boats and they spend their lives somewhat saturated with water, so no surprise a small amount gets into the skin), will simply trap any moisture within where it will eventually decimate the 'new' coating at its interface with the original GRP.

The problem is that no matter how hard a repairer might try, and noting many of them will likely not try that hard, to get the gel coat peeled GRP properly 'dry' ANY moisture left will be trapped in by the new epoxy coating, where this now completely trapped moisture cann then never escape so instead it will do its worse.

So IMHO simpler to find another boat to buy than one that reports a replaced Gel coat - 10, 15 , 20 ... years ago. For me they are in the same category as those with Volvo Penta engines - avoid at all costs.

 

[Simon F]

We have just dealt with the nightmare of osmosis. My boat had osmosis treatment, circa 20 years ago. We have owned her for 13 years and sailed her 42,000nm. We came back to the UK last summer and whilst we were home we opted to deal with osmosis blisters. We needed to do the Coppercoat again but the bumps all over the keel and to a far lesser extent on the hull, suggested it would be a good time to sort the bottom.
A boat that had osmosis treatment 20 years ago may or may not have had a good job. I think ours was probably a poor job. My American boat builder friend calls osmosis treatment "the great osmosis scam".
The difficulty we had was that a failed epoxy treatment needs removing. We couldnt use a gelcoat peeler. We tried, but the epoxy coating was so hard, it could not deal with it. It was at risk of destroying the machine. As a result, we had no choice but to grind off the old epoxy with angle grinders and flap disks. This gets it off OK, but leaves the hull rough. We then waited for the hull to dry out.
What was obvious when you remove the old epoxy coating it how thin it is. Ours was paper thin. There was no way this coating was going to last indefinitely. Think of a boat with 7'2' draft in our case. If you leave a tiny hole in the epoxy, even a pin prick, on the bottom of the keel, the pressure of water trying to get in is pretty high. Even the smallest failure of the epoxy coating will lead to moisture ingress. I think this is what happened to ours.
On advice from my American boat builder friend, he suggested we laminate two layers of 300g cloth onto the hull if you really want to do a proper job.
So, this is what we have just completed.its not a job for the faint hearted. It does mean we have 3mm minimum of epoxy coating on the hull, reinforced with glass. The whole thing is horrendous and expensive. Even though we did a high percentage of the work ourselves, we are still into probably £15k for a 44ft boat. The labout cost from the boatyard to assist has been eye watering.
We are coming to the end of the process. We have another coating of fairing compound going on Thursday, more sanding then hopefully some paintwork at the waterline, then coppercoat.
It will be a rush to get afloat and off south to warmer climes before winter.

.

Hi Geem, I'm sorry you've had such a shocker! I hope the whole wretched business recedes into memory as you set sail for warmer climes. The Mediterranean presumably. Thank you for replying, I'm quickly forming the opinion that a boat with no history of osmosis repair would be my safest choice. I wouldn't have assumed that, honestly, so I'm glad I asked for opinions from all quarters. Fair winds! Simon Forbes.