Is there truth in what I am told re fibreglass?

[hanjae]

Looking around at different boats, I was lookingat one which has sat on the water for a long time. The owner made the comment" Osmosis only starts when frost gets to a hull when there is water content" with a properly painted and antifouled hull not so many problems occur!

What are your thoughts?

 

[bilbobaggins]

Bolleaux!

/forums/images/graemlins/grin.gif

 

[Lakesailor]

Well. he would say that wouldn't he?

Absolute crap of course.

 

[VicS]

Yep never heard that before. "Eight thirds pi R cubed" I would say.

 

[pvb]

Obviously not true, but...

It's obviously not true, but there are a lot of misconceptions about osmosis. First thing to remember is that it's essentially a cosmetic problem - I haven't seen reports of boats sinking due to osmosis! Also, some hulls seem destined to get it, whereas others (used in identical conditions) don't. Antifouling doesn't stop it, but being properly painted with epoxy can help. Don't be put off if the boat's otherwise attractive. Get a survey and see what the hull is like. The fact that it's been sitting on the water for a long time doesn't make any real difference.

 

[Clyde_Wanderer]

Correct Osmosis never sank a boat, but try telling that to an insurance company.
I carried out a complete hull relamination on an old Crossbow 15ft centre boarder a few years ago, and in the process of the restoration removed aprox 300 osmosis blisters, then relaminated the entire wetted area of the hull to twice the original thickness, before regel coating it.
Osmosis is a chemical reaction which sets up when water penetrates through the gell coat ( which is porous to some extent) the water mixes with the chemicals in the resin and produces a vinigary type of acid which expands and causes the blisters, since the laminate inboard of the blister is usually thicker than outside it the blisters force outwards, and have been known to contain pressures of up to 60psi withen some blisters.
Mind osmosis is not to be confused with wicking which is another story.

 

[Avocet]

If anything, I've heard it is often WORSE in boats that have spent time in warm waters like the Carribean!

 

[oldsaltoz]

G'day JonathanGM,

What a lot of old cobblers. You ask him to explain how boats in here Australia in areas that have never ever seen a frost let alone ice still develop Osmosis.

No doubt any pockets of trapped water in a hull would expand if frozen, but it would have to be a good volume.

Most blisters are formed not from freezing but from heat as the moisture in wicking is transported via capillary action, when the temperature rises it can not get out so causes a small local delamination, we see this as a blister.

Avagoodweekend......

 

[alienzdive]

Alhtough this has not been proven but it is somthing under consideration from the resin and glass manufacturers as the only way to really stop osmosis is by changing the formulations or application at manufacture stage.

In the 70's talc was used in the resin mix in higher concentrations than today. They reduced the quantity as this was thought to be the cause of osmosis. They then had to wait 10 approx years to see if this had solved the problem. Which it had not. This is where the big problem with finsing a cure lies. Every time they modify or change somthing, they then have to wait to see if the problem is solved.

Lots of time has also been spent looking at the way the fibreglass strands absorb moisture prior to application. Although there is further continuing research in this area and many yards have changed the way that it is stored as well as the manufacturers have changed the packaging etc, which in turn has they believed improved teh overall quality of teh glass mixture, but still has not resolved the osmosis problem.

 

[andy_wilson]

BS!

That's what.