Osmosis?

PaulJS

PaulJS

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As a marine engineer I have only worked on steel hulled vessels, and as a novice sailor I only have experience of a plywood dinghy (Admittedly patched with glass-fibre!), but I've just seen another thread about the "dreaded osmosis"...
So can anyone explain what the consequences of leaving osmosis in glass-fibre hulls untreated would be. Would the hull suffer from structural degradation or would it start leaking? Could osmosis leave the laminate subject to the possibility of catastrophic failure, or would it be a more gradual damage?
Basically my question is can osmosis seriously harm a yacht, or is it more a cosmetic issue? If it is a symptom of the layers delaminating I appreciate that it could be harmful, but if it is localised damage with only pinpoints of damage surely it is relatively unimportant.
Any advice from more experienced forumites would be worth reading.
 
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Osmosis`

As I understand it osmosis is really only a cosmetic issue. Perhaps theoretically after many years the structure could be compromised but I guess fibbreglass has not been around long enough for anyone to know! Fibreglass boats are over engineered in thickness of f/g to get sufficient stiffness in the hull. olewill
 
Most Osmosis Is Probably Cosmetic and De Lamination Probably Poor Build Quality

The surveyor picked up elevated moisture readings in the hull at the quarters. The boat had some blisters removed by the previous owner. In my investigations into whether I should be worried or not (in order to buy) the opinion was firmly that I should not be worried because the boat was from 1973, the blisters were just minor surface imperfections and anything serious such as massive osmosis would have shown up by now.

Obviously there is a lot of stuff on the web about this but it is worth searching and reviewing. The overall impression from a web based search was that in most cases cosmetic damage is all that's occurring.

I discussed this with a very respected Clyde based surveyor (published) who summarised as "buy the boat, go sailing and enjoy it - she is not going to fall to bits"

Even with 20 mm diameter blisters, if they are pricked and dried it would still be cosmetic. There was good stuff about drying out too. For example you have to wash frequently with fresh water as the salts in the osmotic fluid if not washed away simply soak up water again.

The web search also highlighted that de-lamination is more than likely due to poor lay up and is a separate problem from Osmosis but that the forces involved in creating osmotic blisters can exploit weaknesses and create de-lamination.

So my conclusion was that in many cases its likely to be cosmetic, de-lamination is probably due to other factors in the build lay up. I made the commitment and bought the boat.

As for moisture readings in the hull - that whole subject is apparently full of pit falls and to be only told that moisture readings are high is about as much use as a chocolate fire guard - but that opinion is only from a web based search on the subject and not from any personal competency on this matter.
 
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Purely cosmetic, as far as i know no boat has sunk because of it. I reckon its just used by buyers to knock the price down and surveyors/boatyards to earn money.
 
Thanks everyone

You all seem to be thinking the way I was, but there are an awful lot of posts and magazine articles referring to various ways of treating osmosis.
Mind you, I suppose that if I'd paid hundreds of thousands of pounds for a yacht, I would be very distressed if blisters started appearing on the hull!! :)

Paul
 
PaulJS said:
You all seem to be thinking the way I was, but there are an awful lot of posts and magazine articles referring to various ways of treating osmosis.
Mind you, I suppose that if I'd paid hundreds of thousands of pounds for a yacht, I would be very distressed if blisters started appearing on the hull!! :)

Paul
Click to expand...

My boat has osmosis, about 7 or 8 blisters on an Ocean 30 which is 40 years old. Oh God, what to do, answer - slap some acne cream on it and go boating!

In other words, unless the hull is so poorly made in layup that it is resin poor, so delaminating and weak anyway, only the fishes will see the minor imperfections. Older boats were over-engineered, thank God, given the times I clout lock walls and so on, more modern ones with economic restraints on build cost were engineered to be suitable and sufficient, i.e. lighter. Not uncommon to see daylight glowing through the hull but that is more a factor of less pigment than less thickness!

Enjoy your boat!
 
Boat Pox

1. It is cosmetic, buyers will use it to knock down the price, moisture readings are about useless.

2. Every fiber glass boat built during the age of polyester has or will have some degree of osmosis caused by glycol in the layup. The only proven method for removing the glycol is the Hot-VAC system (www.hotvac.com).

3. If you own the boat and want to go sailing, do it--no worries. If you are going to be selling the boat, think about the cost/trouble of restoration -vs- price knock down at sale.

4. If you're looking to buy a boat that has blisters, go for the price knock-down, the guy you sell it to will.

VBR, Thistle
 
PaulJS said:
You all seem to be thinking the way I was, but there are an awful lot of posts and magazine articles referring to various ways of treating osmosis.
Mind you, I suppose that if I'd paid hundreds of thousands of pounds for a yacht, I would be very distressed if blisters started appearing on the hull!! :)

Paul
Click to expand...



Paul...I've been in the yacht construction/repair game now for thirty years, and my personal view on osmosis is that it's a problem but over hyped. As with all boat building materials GRP has it's bogey word 'Osmosis', but compared to rust & rot, I know which one I'd rather have.

Sure, buyers use it to knock down prices, paint manufacturers and boatyards make money out of it's repair & prevention, but it hasn't sunk boats to my knowledge (might make them a little heavier due to wicking). Which, at the end of the day is pretty important...don't you think.

Over all those years, I've only seen one boat that was so seriously de-laminated as to be downright dangerous. That boat had sat on a mooring in the South of France for the majority of it's life and was shipped back to the UK on a lorry. You could literally push in sections of the hull with your hand. But that wasn't caused by osmosis. In fact there wasn't a blister in it. It was purely a laminating problem. Could have been moisture or poor resin/catalyst at the time of layup.

As for blistering. I've seen blistering on decks and coach-roofs, but that's not osmotic wicking. It's a gel/resin-catalyst problem. Beneteau had a particularly nasty couple of years in the mid eighties and had to call over 600 boats back in because the wrong catalyst was used. This resulted in blistering above and below the waterline.

As has been said, there's a wealth of information out there on the subject. Google...Tony Staton Bevan, he's done a lot of work on the subject. But again don't be put off by all the scare stories. After all, if we all obsessed over the warnings given in Admiralty Pilots, nobody would ever go to sea.
 
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Hi

I have a Jeaneau SunMagic I bought her 15 years ago . It had small blisters then .The Surveyer said it was common for Jeanneau to have blisters I made a reduced offer and bought her . Every time we lifted her for the winter layup ,the various yard in Greece always said Mister you have big trouble with this boat And wanted to quote for repairing her. In the begining 4-5000euro now 10000euro

The problem is, there is no problem, the boats small blisters are still about 2-3mm and the same quantity as 15 years ago

They have never been an issue with me or the boat ,But to the yards they appear to be a cash cow.

cheers bobt
 
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My Westerly has thousands of tiny blisters which are less that 1mm deep,By looking at them one can see they were caused by trapped air when te gelcoat was rollered on because there's a very clear pattern to them.The laminate underneath is absolutely sound and what's more they haven't grown in size for the last 8nyears.So I'm not spending money fixing them and if I ever sell the boat I'll either fix the problem or reduce the price whatever is cheaper.I've seen two boats where the laminate was failing,both built in Taiwan.In both cases the bad laminate caused osmosis not the other way around.
 
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PaulJS said:
Any advice from more experienced forumites would be worth reading.
Click to expand...

No it wont't . You will get a lot of hearsay, some biased comments from those with wet boats and possibly be referred to web sites that sound authoritative but arent. Even the resin suppliers arent always that well equipped - when I had a visit from the tech manager of one supplier to look at coating problems on my boat , I expected to be talking to someone with maybe a PhD in the subject. What I got was someone who's tech qualiifications were a few years moulding dinghies.

With a tech background I have searched high and low to try and find a really convincing answer to the question, and so far I've failed. The only practical comment I can make is to say that a pal has osmosis in a Sadler 29, and when I gently removed the hydrolised resin / fibre mix from the hole ( gentle scraping with a tea spoon and I could have used a finger nail) I went a good half way through the hull. So I just can't see how anyone can say it is purely cosmetic.

And as for the "none have ever sunk" argument. Would you tell your insurance company that your boat might have sunk because of osmosis when that would mean the claim wasnt paid?

I suspect its a slow process. I suspect its mostly not serious - a wander round our club compound in winter with a moisture meter in hand showed that 90% of hulls were wet to some degree. But I am absolutely sure it can be serious in the worst cases and left untreated.

Last comment - the only thing you can do to grp that cant be repaired is to set it on fire. If you have serious osmosis, I'm sure it can be repaired and the hull sheathed with epoxy / woven cloth. It's all just a matter of money.
 
Quote:
Originally Posted by William_H View Post
Fibreglass boats are over engineered in thickness of f/g to get sufficient stiffness in the hull. olewill

Quote:
When you are in the lazarette and you can see daylight through the hull you wouldn't think so!
Cheers,
Chris.

I doubt you would ever ever see any Osmosis in the walls of your boat unless you have been on the same tack for many years. The area needs to be below water for osmosis to form. Oh and it can from inside and well as outside, so keep your bilge dry.

Avagoodweekend......:)


.
 
oldsaltoz said:
Quote:
Originally Posted by William_H View Post
Fibreglass boats are over engineered in thickness of f/g to get sufficient stiffness in the hull. olewill

Quote:
When you are in the lazarette and you can see daylight through the hull you wouldn't think so!
Cheers,
Chris.

I doubt you would ever ever see any Osmosis in the walls of your boat unless you have been on the same tack for many years. The area needs to be below water for osmosis to form. Oh and it can from inside and well as outside, so keep your bilge dry.

Avagoodweekend......:)


.
Click to expand...

Wasn't talking about osmosis but the thickness (or should I say lack of) of the hull construction. Agree strongly with the osmosis is cosmetic school.
Cheers,
Chris
 
Not sure you need to be below water for osmosis to occur. I had extensive osmosis to the roof of my Matra sports car a few years back! A respray didn't cure it either; the blisters reappeared.
 
Sorry to upset the apple cart.. BUT osmosis is like a CANCER, if left un-treated it can and usually gets worse. The blisters caused by OSMOSIS are full of water...SALT water. Salt has a nasty reaction to water.. it draws more in and so the problem grows.

Sorry to put a damper on all the ''dont worry brigade'' If you do have ''OSMOSIS'' Remove all blisters, dry out, wash with lots of FRESH water, dry out and then repair.

Peter
 
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