Osmosis Advice please

[Guest]

I am about to buy my first boat 29ft, 1982 my dream boat an I am in Love! The price is right but the survey which was done when the boat was taken out of the water suggests osmosis may be a problem in the future. The boat has now been out of the water for 8 months so she had dried out I have had two conflicting suggestions re my problem.

One suggests I leave it put the boat back in the water enjoy my sailing and sort out the Osmosis when it appears ,on the basis that any 20 year old boat will have it one day

The other says I should have epoxy treatment NOW while she is dry this will prevent Osmosis for up to 15 years.

Could some of you old hands please give me some advice what would you do.

Thanks James

 

[Guest]

Polyester hydrolisation

Who told you that a dried out boat on the hard would be susceptible to the dreaded misnomer 'osmosis'? (My boat a Jeremy Rogers 1968 is as sound as sound can be - she surveyed every year and the moisture meter still reads reads zero)

'Osmosis' in GRP is stagnat water getting into the voids and hydrolising it creating 'vinegar' plus expansion.

The boat that you want has a price. If the AYMSDA Surveyor of your choice says that it has a potential Osmisis problem, then all you've got to do is to get a quote for slurry blasting and re-epoxying. Deduct this plus 10% from your offer which should be at least 20% less than the asking price if you are going through a broker ...

NigeCh (RogueWave Inc)

 

[Guest]

osmosis is better treated as soon as possible.*

*

 

[Guest]

Only if you have it.*

 

[Guest]

Dont worry about it. From what you say it sounds as if the Surveyor is just covering his ass. Go for it and happy sailing.

 

[Guest]

The \'leave it\' school wins.

There is no guarantee that, even after 8 months out of the water, she is dry enough to treat.

If she has no osmosis (or whatever you care to call it, boat pox is as good as any in my view - scientifically speaking it is not osmosis)she is unlikely to develope it to a sufficiently serious degree to require immediate action for afew years. If you do treat it now, you won't get a guarantee of more than five years, maybe only three, from the people who do the job, so you could be just throwing money away. Pox treatment may last for 15 years but, as I found to someone elses cost, it can also last just two years.

In my view, and this is slightly controversial, if your boat gets pox in, say three years, I would not bother with treatment for at least another three or four years while monitoring its progress carefully. Indeed, unless it got very advanced, I would leave it until the boat came to be sold then price her to allow for the new owner to do the job if he wished. It is extremely rare for pox to be so bad as to threaten the structural strength of a hull boat.

 

[Guest]

That\'s a refreshingly sensible post to find on this BB. (nm)

 

[Guest]

Most boats of this age will have absorbed water moisture. A couple of hundred pounds weight is not uncommon in a 30'. I'm afraid that this is a fact of life which should be allowed for.

However, water moisture absorption does not lead to osmotic blistering (as NigelCh says) - the causes of which are not clearly understood - instead it could be Polyester Hydrolysis or even water accumulating in voids in an inert manor (like water in a sponge).

Has the anti-fouling paint been stripped off and the boat stored undercover?

If not, I doubt (esp with the amount of rainfall we have had recently) that the hull will have been dried sufficiently during the past 8 months.

If you buy the boat, either get the antifoul blasted off and leave it for 3 months over the summer and then have preventative epoxy paint treatment or sail it over the summer and then get it dried properly over the winter.

Of course it could be the surveyor covering his back...

 

[Guest]

On what you have told us you do not have osmosis - yet; this would be visible. You have a surveyor who, like many in the profession, has proabably looked at the age of the boat and advised you to take care; reasonable enough. But is this a direct call to action?

Clearing off the hull and applying 5 coasts of 2 pot is no small undertaking, but you will feel better having done it, any future purchaser will be somewhat reassured, and any moisture in the hull will likely not increase as much as if you took no action and sailed on. This is what I did; and 8 years later the boat sold easily and without suveyor caution, because there was no deterioration.

I suggest you do not take a dismal view of your prospects at this stage - you appear not to have grounds for such.

Peter Gibbs

 

[Guest]

Found a site that appears to be give practical advice on osmosis and surveying. www.turbolink.co.uk and look for the marine survey page. Brian Jessop

 

[Guest]

I take it you've asked your surveyor to tell you exactly what he means by "may be", "problem", and "in the future". He's an engineer of sorts. Should be able to put some ballpark numbers in there. If he has no evidence, he should say so. If the boat is from a builder with a bad reputation for this, he should tell you. Blistering problems mainly arise from poor control at the manufacturing stage and hulls which have been moulded in properly controlled conditions seldom suffer. Even where problems exist, the action required is, I believe, seldom as drastic as the fixers would sometimes suggest. Whatever you do, absolutely do not use a solvent based epoxy as a preventative barrier. The previous owners of my boat did this and got away with it. According to my surveyor, had there been an incipient problem there, they would have had a major disaster on their hands; whereas - hope it works this way! - I got a boat that's been tested to the edge AND has an impermeable barrier. Certainly, 12 years on I've no signs of blistering in a 22 year old boat.

 

[Guest]

"If the boat is from a builder with a bad reputation"

So who are the builders who should be avoided and, on the other hand, those with a quality record when it comes to this osmosis stuff???

 

[Guest]

Dangerous territory

Don't know whether the site can stand a "name and shame" thread. Doubt it. On the other hand.... A few years ago, I read a review of the old Princess 32 motor cruiser from which a comment stuck in my mind that osmosis was virtually unknown in them or other boats from the same stable, the stable being Marine Projects in Plymouth. Since the mid-70s, almost all Moodys and Sigmas, and goodness knows what else, came from this builder. I'll vouch for one Marine Projects Moody from 1979 showing no symptoms: haven't a clue about the rest, other than I've heard no complaints.

 

[Guest]

Talk to Paul Hockey on Symblast site and have a look at www.yachtsurvey.com - this is an excellent American site which amongst many other topics covers blistering. They do not call it osmosis. In your position I would bight the bullet and slurry blast and epoxy if only for peace of mind and to make a future sale potentially easier.

 

[Terence Davey]

I am about to buy my first boat 29ft, 1982 my dream boat an I am in Love! The price is right but the survey which was done when the boat was taken out of the water suggests osmosis may be a problem in the future. The boat has now been out of the water for 8 months so she had dried out I have had two conflicting suggestions re my problem.

One suggests I leave it put the boat back in the water enjoy my sailing and sort out the Osmosis when it appears ,on the basis that any 20 year old boat will have it one day

The other says I should have epoxy treatment NOW while she is dry this will prevent Osmosis for up to 15 years.

Could some of you old hands please give me some advice what would you do.

Thanks James

From Terence Davey
I have read the many replies to the above posting and am astonished to discover the subject of osomosis in polyester-glass mouldings remains the subject of so many myths and so much ignorance.

1. So called osmosis is no more than the slow decomposition of the materials of the moulding through instability. This may be speeded up by the presence of moisture, floating in warm water or the unusally high number of the tiny voids that are always present in g.r.p.!


2. Excluding the presence of moisture from the moulding is not only impossible, but effective desiccation (also impossible) would not arrest the decomposing reactions in g.r.p when the decay has become significant.

3. Polyester of even the simplest formulation is when effectively cured, very stable, resistant to acid and likely to have an indefinite service life if it is not stressed unfairly by poor design or unfair usage.

4. The reasons for instability of cured mouldings are beyond numbering but the most common are poor formulations, errors in mixing and low temperatures during the cure.

5. Most peel and paint treatments are merely cosmetic and the high strength-high build paint films slow the reaction for a while and also prevent the pressure of the decomposition from being apparent.

Conclusion: If you have a sound but blistered boat use it and be happy, but accept it may have a slightly lower resale value.
If the structural integrity of the boat is likely to be compromised by the decay, then it should be radically peeled and the remaining sound material (assuming there is any) can be used as a base for reconstruction using epoxy-glass.

TD

 

[GrahamM376]

Sounds like the surveyor is covering his backside, either it has or hasn't got osmosis. Many older boats will get it (my Centaur and Berwick both had) but it's not the end of the world and treatment is within the capabilities of most DIY owners anyway.

If the hull has been dried out for 8 months and has low moisture content with no blisters, it may be worth DIY epoxy treatment now which would slow down moisture absorption over the next few years.

 

[Racecruiser]

Probably worth telling the forum what the moisture readings are - if high I would suggest caution.

 

[fireball]

you're picking a 10 year old thread up and commenting as though it is current thoughts ...

Seems to be a trend recently ...

 

[Terence Davey]

Sounds like the surveyor is covering his backside, either it has or hasn't got osmosis. Many older boats will get it (my Centaur and Berwick both had) but it's not the end of the world and treatment is within the capabilities of most DIY owners anyway.

If the hull has been dried out for 8 months and has low moisture content with no blisters, it may be worth DIY epoxy treatment now which would slow down moisture absorption over the next few years.

DIY epoxy treatment can make blisters far more obvious and more corrosive. If your boat is not blistered or appreciaby weakened. Leave it alone.
Osmosis is not a matter of 'have it or not'. Hull blister symptoms are not anything to do with osmosis.
Yes, epoxy coatings do slow down the rate of moisture adsorption.
Most so called osmosis claims are degenerative reactions in gelcoat and superficial erosion of the 'skin out' laminate by acidic blister fluids.
Effectively permanant repairs can be made by peeling off the gel and damaged 'skin out', removing the residues of decomposition by steam cleaning or heat in vacuum, then recoating after replacing the skin out laminate with epoxy-glass.
Unfortunately, it is not unusual for a surveyor to diagnose 'osmosis' and then tell the buyer that the boat will be OK after it has had an 'osmosis treatment'.
That has been the ruin of many and especially, the boatyards who guarantee such repairs.
Decomposing hull mouldings can only be detected by intrusive testing. That is: core sampling or cone shaped drillings.
If a boat is found to be so affected when it is peeled, then the cost of repair (given that a repair is possible) may be more than the value of the boat.

TD

 

[Terence Davey]

you're picking a 10 year old thread up and commenting as though it is current thoughts ...

Seems to be a trend recently ...

Thanks, but these threads come top of the search list when people look for "osmosis advice" and there should be some informed opinion that is up to date. I hope I have provided it, even though it is at the end of a string of not very helpful comments.