Osmosis (again!)

[Allan]

As I understand it, old boats can suffer from osmosis and due to a change in materials, new boats should not. Is there some way of telling which boats are made using the later material? Is there an approximate date to look out for? Many thanks in advance.
Allan

 

[stevebrassett]

Not as easy as that. As I understand it, the problems with osmosis occur when the boat builder tried to cut costs, either by using cheaper resins, or by skimping on the layup. Therefore, older, well-built boats may not suffer, and nor will more modern boats where the builder understands the problems. Most problems are found with boats in the 80s and 90s. That is a gross simplification, and someone will be along soon who knows more about it than me.

 

[boatmike]

Totally wrong assumption in the first place!
Materials used have improved somewhat, techniques like vacuum infusion have helped too, but there is no one reason for so called osmosis and its a very complex subject. In fact some older boats built well and looked after never have a problem and there is no one point in time or any revolution in boatbuilding that has happened to say boats built before this date are suspect and afterwards they are OK

 

[Stemar]

Far more than you wanted to know about osmosis here

 

[wotayottie]

Round about the end of the 80s, many big manufacturers moved from ortho resins to iso which made an improvement, but different manufacturers changed at different times and there are other resins like vinyl ones - as well as epoxy which is an entirely different animal. Plus all resins have improved since the early days.

As I understand it, the only one to be osmosis proof is epoxy. All the polyester resins are vulnerable, and what varies is the speed. And the way the boat was built. And fresh / salt water. And water temperature.

You're on a hiding to nothing if you try chasing this issue. The best you can manage is "has this boat got the pox or not?". Trying to buy one with less future risk cant be done because there are too many variables.

Good article on the subject in a recent pbo

 

[flyingscampi]

I bought a boat with some pimple sized signs of osmosis. My surveyor said you'd be hard put to find a boat 20 years old without it. I got some money off the price and this gives me a fighting fund to treat it if it shows signs of becoming any worse.

As it is I'm leaving it well alone.

From the articles I've spent hours reading and from advice from some wise old heads in boat yards I'm not going to spend 7k stripping the bottom off the boat unless I have plum sized blisters all over the place.

 

[alan006]

Yes, wotayottie, there were 2 good articles about osmosis in PBO in December'07 and January'08 magazines. I learnt a lot from them.

 

[graham]

With the decline of wooden yachts to repair the boatyards needed to find something profitable to do so they invented Osmosis treatment.

As far as I know no boat ever sank because of it.I have also known boats supposedly "treated" at great expense where the problem has reoccured.
Wood rots Steel rusts GRP needs much less maintainence but gets Osmosis ,take your choice.

 

[retsina]

My Macwester is boat is 37 years old; no osmosis at all; it appears that workmaship had a lot to do with this issue. Any way, no boat has sunk because of osmosis

 

[m1taylor]

I think that's good advice there. Actually even epoxy is not immune - eventually it may be damaged, thinned or affected in some other way. But these things take a very very long time. Unless there is a real issue with poor manufacturing (unlikely), I think the best ploy is to ignore the supposed 'problem'. A boat builder I knew told me that quite often more problems are caused with repairs, than just leaving it well alone.

 

[Grajan]

Boats have sunk because of "Osmosis" I know of at least two
but normally it is because the laminate has softed so badly that appendages either fall down or keels fall off!

 

[Longshanks]

[ QUOTE ]
Boats have sunk because of "Osmosis" I know of at least two
but normally it is because the laminate has softed so badly that appendages either fall down or keels fall off!

[/ QUOTE ]

I've always doubted these glib "never sunk" statements as well, BUT I do believe it would be a VERY rare occurrence and need massive delamination of the hull to have occurred. What does of course sink is the value of your boat, even if this is totally irrational in many cases. The yachting press and surveyors are fundamentally to blame here IMHO. In my case, apart from one small area where they are more prevalent, the number of (tiny) blisters on the hull can be counted on one hand..and were completely invisible until the AF was removed, and only then because the epoxy coating is grey and white patches show up easily once the pimple heads have been scraped off. I suspect that virtually every boat more than about 20yrs old has some of these, and most owners / buyers don't know it. I'm pretty sure they were there when my boat was surveyed some 3-4 years ago, but unless the surveyor happen to scrape that patch, he won't know (moisture levels were moderate and didn't raise any alarm bells).

 

[m1taylor]

Well, it's very rare. The osmosis in those circumstances is more than just pimples, and actually is more related to wholesale delamination, precisely because of what I said about poor manufacture. If you have a boat in this very rare category, you would know about it - it wouldn't just creep up on you.

 

[Grajan]

I quite agree with you with regards to it being a rare occurrance but both of the vessels were being used when they sank, well they managed to beach the motor boat ! and after some hefty relamination it lived to sail again The point I am trying to make is that neither of these boats were showing signs of blistering when the integrity of the hull failed and were involved in making lengthy passages when disaster struck
in my opinion, based on 30+ years in the Yachting Industry, all 20+ year old boats have some form of laminate failure (some with no visible indication) which, when put to the test, could fail under arduous conditions, wether that be by being caught out in severe weather or falling off a ferry wake.
Fortunately I do not know of any loss of life, but keen amateur sailors must not be miss led into thinking that it doesn't happen, especially as these older boats become more affordable.