Osmosis?

[PaulJS]

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.

Hi Phil, I can't really see that as being caused by osmosis because osmosis, and reverse-osmosis depend on there being a pressure differential across the interface. ? Maybe there were exposed ends of the glass fibres wicking in rain water before paint had been applied?
I could be wrong of course...

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

Hi Peter, Good to hear from someone with a different viewpoint.

 

[rivonia]

Hi Phil, I can't really see that as being caused by osmosis because osmosis, and reverse-osmosis depend on there being a pressure differential across the interface. ? Maybe there were exposed ends of the glass fibres wicking in rain water before paint had been applied?
I could be wrong of course...




Hi Peter, Good to hear from someone with a different viewpoint.

Hope that it is not ''OSMOSIS'' Good luck and fair winds

Peter

 

[oldsaltoz]

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.

G'day Tobermoryphil,

This sounds more like wicking than osmosis, moisture travelling along exposed ends of fibreglass, jest sanding and re coating will net remove the moisture, so the blisters will return soon after exposure to sun on a warm day.

Avoid re coating till all moisture has dried then seal with an epoxy followed by a primer, then paint for many more trouble free years.

Most if not all blisters above the water line are due to either trapped water migrating from below the water line due to being sealed when still moist, or moisture trapped under the coating when applied.

Hope this helps.

Avagoodweekend......

.

 

[saxonpirate]

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

Taking your cancer analogy first. Cancers are either malignant or benign. One will kill you the other won't. Of course nobody wants a problem with their boat, especially the hull, but the osmotic transfer of water molecules into the laminate doesn't kill boats. Devalues them and makes them heavier yes, but it doesn't make them unsafe. Unlike rot or rust.

The process of osmosis in GRP boats is incredibly slow, unless the hull is particularly badly made. It doesn't matter how long a boat remains afloat, a typical GRP laminate cannot absorb more than about 2-3% of it’s own weight of water. Even completely saturated with water, a GRP laminate still retains most of it’s strength.

Of course, if you can get the chance to carry out repairs and make good, do it if it gives you peace of mind. It's the way to go. But I'm just trying to inject a little perspective into this argument, because so many boat owners are intimidated by the dreaded word OSMOSIS. As I said in my earlier post, it's hyped out of all proportion.

 

[rivonia]

Taking your cancer analogy first. Cancers are either malignant or benign. One will kill you the other won't. Of course nobody wants a problem with their boat, especially the hull, but the osmotic transfer of water molecules into the laminate doesn't kill boats. Devalues them and makes them heavier yes, but it doesn't make them unsafe. Unlike rot or rust.

The process of osmosis in GRP boats is incredibly slow, unless the hull is particularly badly made. It doesn't matter how long a boat remains afloat, a typical GRP laminate cannot absorb more than about 2-3% of it’s own weight of water. Even completely saturated with water, a GRP laminate still retains most of it’s strength.

Of course, if you can get the chance to carry out repairs and make good, do it if it gives you peace of mind. It's the way to go. But I'm just trying to inject a little perspective into this argument, because so many boat owners are intimidated by the dreaded word OSMOSIS. As I said in my earlier post, it's hyped out of all proportion.

As I stated in my post ''OSMOSIS'' is LIKE a cancer I did not say it was a cancer. If you had benign prostate hyperblasia would you leave it un treated?. It is a benign cancer BUT can change at any time to MALIGNANT cancer. Back to ''OSMOSIS'' if you have it GET RID as it WILL spread.

Peter

 

[jb2006]

In the UK I always assumed osmosis to be a disater scenario - however, here on the East Coast of Australia with 25degC water it is just an accepted fact of life as osmosis is greatly accelerated in warm water. It is still a negotiating point and personally I would fix it properly but people generally seem to patch it up year on year rather than go for the HotVac treatment. It spoils the fair underwater finish of a race boat but in a older boat other than one you are trying to sell I wouldnt worry too much. When I was looking to buy a boat here, the view was that I needed to get the price down to cover the cost of a full repair but could reasonably just do the annual cosmetic repair and pass on the cost saving when I sold the boat.
It will get worse with time - and eventually somone will have to bite the bullet of the full repair.

The bubbles of osmotic fluid can cause some delamination which in extreme cases can lead to a loss of integrity of the hull.

 

[CAPTAIN FANTASTIC]

I am not aware of any yacht which has sank because of osmosis.

 

[1bobt]

I am not aware of any yacht which has sank because of osmosis.

Hi
I am in this camp.
Osmosis happens its like old age some boats get it some don`t show it, but they all die of something .
In my experiance, it is the way the marine industry gets good hard earned money out of gullible people by frightening them with disaster tales, to spend in their yards. look at all the metal boats made in the fifties and sixties very few if any left ,wooden boats need lots and lots of money thrown at them to keep them afloat.

Don`t worry over a bit of acne!!
cheers bobt

 

[Ubergeekian]

As I stated in my post ''OSMOSIS'' is LIKE a cancer I did not say it was a cancer. If you had benign prostate hyperblasia would you leave it un treated?. It is a benign cancer BUT can change at any time to MALIGNANT cancer. Back to ''OSMOSIS'' if you have it GET RID as it WILL spread./QUOTE]

Evidence, please.