Osmosis- the truth

Osmosis the truth!

  • It doesn't really bother me if its got osmosis.

    Votes: 45 38.8%

  • I wouldn't go near a boat with osmosis.

    Votes: 27 23.3%

  • Osmosis is hyped up and treatment is a con.

    Votes: 50 43.1%

  • I don't really know what osmosis is.

    Votes: 0 0.0%
  • Total voters
    116
  • Poll closed .
single

single

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Has anyone got any real evidence of boats sinking or becoming dangerous due to osmosis? I'm basing this on an average 1970s cruising yacht with average typical blistering (not the whole hull delaminated).All i can see is a moneymaking scam by boat yards making it sound so severe that if its not fixed thats the end of your boat.Trouble is now the insurance companies have been taken in too.I can understand a surveyor having to do a write up but even they make it sound really bad to someone looking to buy a boat.What are your views?
 
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Fibreglass laminate is only as good as its gelcoat, which must remain waterproof to protect the inner part of the laminate. Osmosis is generally related to some failure of the gelcoat, either due to bad formulation, poor layup or subsequent damage. The widespread use of unpigmented, transparent isophthalic resin since the mid-1970s has significantly reduced the risk of gelcoat failure, but it is more likely where the gelcoat is pigmented. The risk is reduced by adding a coat - or several - of epoxy paint, but this must be done to a new, or definitely dry hull. It's more likely to occur in a boat that's kept afloat 12 months of the year, less likely in a boat that's hauled out for the winter.
The problem with osmosis is that it lets water into the GRP matrix. This weakens the matrix, and also renders it very liable to frost damage. The seriousness of the problem varies from boat to boat, it can be easy to resolve or can be a major problem. It's not, however, a boat yard scam. The effect it may have on a boat's value will depend on how serious the damage is, and how much it may cost to fix. As far as insurance is concerned, it's unlikely to render the boat too dangerous to sail, so 3rd party cover should be obtainable, but as the value of the boat will be less than any similar boat without the problem, insurers will certainly take it into account when determining the level of total loss cover.
 
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This approach to any subject just polarises extreme opinions and none of your poll alternatives are worthy of support. You should ask yourself perhaps if you would buy a car with rusty bodywork. It would be stupid to turn down a bargain because an otherwise good car had easily treatable minor areas of rust. If it was extremely rusty and the price was too high it would be an unattractive proposition but so would one that had no rust and was too expensive. Either way it would be stupid to blame the body shop for doing a respray at a reasonable cost and that is what your comments suggest. It's not a "scam". It's treating a problem that older GRP boats suffer from just as rust appears on older cars.
 
It depends: big blisters/thin hull, problem. My boat has a lot of small, 10-12mm blisters, the same for the last 20 years. A surveyor said 'given the build, no problem'. However if you have a thinner hull moulding and the blisters are large the damage could be right through, and I have heard of some being scrapped. Certainly the hysteria about it has subsided in the last 20 years.
 
single said:
Has anyone got any real evidence of boats sinking or becoming dangerous due to osmosis?
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Yes. I do. I have poked at blisters on a Sadler 29 where the degradation of the laminate has gone at least half way through.

But you carry on believing that everything is a scam, and everyone out there is lying to you. Cynicism is the modern fashion.
 
single said:
Has anyone got any real evidence of boats sinking or becoming dangerous due to osmosis? I'm basing this on an average 1970s cruising yacht with average typical blistering (not the whole hull delaminated).All i can see is a moneymaking scam by boat yards making it sound so severe that if its not fixed thats the end of your boat.Trouble is now the insurance companies have been taken in too.I can understand a surveyor having to do a write up but even they make it sound really bad to someone looking to buy a boat.What are your views?
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I can't quote chapter and verse, but this question has been asked on here before and the answer seemed to be:

  1. It won't sink most boats BUT
  2. There have been rare examples of boats sinking because of osmosis.

I recall this coming up sometime in the last couple of months on here, so a Google search on the forums should find it. In fact, HERE it is.
 
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The subject is far too complex for any simple questions to yield any useful information. There is masses of material available on the subject for you to make up your own mind - or at least understand what the issues are.

And yes, the answer is that boats can be severely compromised by a failure of the laminate which usually stems from poor materials or poor processes when the mouldings were made. Often this is not discovered until long after the boat is built, and often only when the surface defects are being treated, which exposes the failed laminate underneath. There are probably many boats in use with undiscovered internal laminate failure.

Improvements in materials and processes in the last 25 years or so has resulted in much better mouldings, so the issue is less important now than it used to be.

As to the effect it has on the boat and whether you do anything about depends very much on the individual boat and its value.
 
single said:
Has anyone got any real evidence of boats sinking or becoming dangerous due to osmosis? I'm basing this on an average 1970s cruising yacht with average typical blistering (not the whole hull delaminated).All i can see is a moneymaking scam by boat yards making it sound so severe that if its not fixed thats the end of your boat.Trouble is now the insurance companies have been taken in too.I can understand a surveyor having to do a write up but even they make it sound really bad to someone looking to buy a boat.What are your views?
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'Osmosis' would have to be very, very bad indeed to endanger the hull integrity of (for example) an old Nic 32 or Seadog - both grossly overbuilt in hull layup by modern standards. I owned and sailed a boat much like this with blisters for 12 years. Equally however I'd worry a little if a modern thin hull had anything more than small surface blisters, and I'd prefer none.
 
Osmosis

If I am buying a boat it is a deal breaker and if I am selling then I'll see how much the buyer wants me to move on the price to help him feel comfortable.

Basically it is not the end of the world and it has a price.
 
I can't say that it doesn't bother me, but I can't say that I wouldn't go near one either.

My Sadler 34 was found to have quite bad osmosis during the pre-purchase survey which nearly made me walk away. After negotiationg a substantial discount to the original offer and then waiting 9 months for the treatment to complete I am now a very happy and proud owner of a nice dry boat with a new smooth bottom.
The treatment was very worthwhile as it happens because it identified concealed damage to the hull that allowed water through in to the foam and several areas needing repair. This is probably what caused the osmosis to become so bad in the first place.

Osmosis scares me, not so much for it's effect on hull strength, though that is a genuine concern, but more for the effect on my wallet in either treatment costs or reduced sale price in the future.

I would seriously consider buying a boat with osmosis again, but only if it was advanced enough to need treatment, and I would be more aggressive with negotiating the offer price.
 
My take on it (a bit tongue in cheek) is that most 1970's GRP boats have a few blisters and most 1970's wooden boats have long since ceased to exist. GRP is a wonderful material in my opinion. I can neglect my boat to an extent that is almost criminal and it still looks the same. My old boat had a few wooden bits and they constantly showed me up as the sloth I am.
 
If your boat is diagnosed with osmosis, you may have trouble insuring it. It wouldn't bother me at all on a Silhouette but I'd get a bit paranoid if it were a Moody 38. It's also a bugger if your surveyor is adamant that it IS osmosis when you "hae yer doots". Following my experience six years ago, I'd go for a second opinion on my own boat.
 
A boat with osmosis would have to be discounted appropriately, because when you come to sell it, that's what the next guy will expect.
 
greenalien said:
..... The problem with osmosis is that it lets water into the GRP matrix.....
Click to expand...

Can you expand on the frost bit please and why you think that? My understanding is that the water volume is measurable at the molecule level rather than, say, mili-litres. As such damage by freezing is not likely, if it is likely then the hull will be seriously knackered by extreme osmosis and not by freezing water. My opinion is only formed from internet searches and some literature reading, not by any specialist knowledge on this subject. I think that if you have levels of moisture that can freeze, expand and damage the laminate, then the GRP porosity will be akin to a well used dart board.

To the OP - In the stuff I have read there are pictures of delaminated hulls. The delamination I believe was a result of both osmosis and inconsistent application of the resin to the GRP in some instances, but mostly poor application of the resin; at least that is what I determined. Some info and pictures: -

http://www.nauticalweb.com/info/maint/delamine.htm
http://www.classic-fiberglass.com/bigPicPhotos2.cfm?galleryID=12&p=7
http://www.channelpilot.info/foamsandwich.php
 
1973 Albin Vega owner here, no osmosis.

I think the rusty car is a good analogy. I would use it as a bargaining chip, unless its really bad.
 
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