Osmosis never sank a boat???

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Osmosis never sank a boat???

Postby stu9000@hotmail.com » Wed Feb 12, 2003 8:13 pm

Did it really say that? Just bought an old Snapdragon 23 (see it here at www.stu9000.netfirms.com) and I think fresh water has been standing inside the hull for some time. The thing is the previous owner cleaned it up a bit and put a coat of paint over the inside hull.

Can this hide the osmosis?
If Osmosis has happened is it a big deal? I guess not if youre staying in the river but if she handles well I might want to head off to France or Holland. I dont fancy seeing the hull delaminate under me and have to hop into the inflatable at 3am. My girlfriend would never forgive me.

Also, if the hull really isnt up to much I might not want to put much time or money in, just have a seasons fun and sell it for what I bought it for.

And no, I havent had a survey done, and yes that would probably answer my questions :wink:

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That's right - osmosis never sank a boat

Postby Nick » Thu Feb 13, 2003 1:18 am

At least, as far as I know. Anyone want to contradict me?

If your boat had serious osmosis the profile of the blisters would show through any paint job.

The blisters would be in the gelcoat on the outside of the hull, I've never heard of osmosis on the inside of the laminate.

Borrow a moisture meter and take a few readings - it might help to put your mind at rest.

Check out http://www.bluemoment.com/osmosis.html for more information.

Nick 8)


thanks Nick

Postby stu9000 » Mon Feb 17, 2003 7:47 pm

Cheers for the feedback Nick.
Certainly sounds good.
Although Im just reading a book about the Whitbread and about 3 boats retired due to delamination. Guess thats a whole different set game though :wink:

I agree that borrowing a meter is the way to settle things.
Although Im already happier knowing that the blisters would show through the paint job.



Postby Guest » Sun May 09, 2004 7:48 am

the snapdragons were bulit before people new how strong fibreglass is.
they are very heavly laid up. the glass is extremly strong in most snapdragons.
i drilled a hole for a paddle wheel log and the glass was an inch thick in the bilges.


Postby alienzdive » Mon Dec 26, 2005 2:49 pm

Correct me if i am wrong but I thought that osmosis could only occur in salt water.

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Postby Silkie » Tue Dec 27, 2005 10:56 pm

but I think you are wrong. In fact, IIRC, the process can be faster in fresh water due to the greater density differential between the water outside the hull (fresh water being less dense than salt) and the fluid in the blisters.

There are several good articles on BlueMoment's Osmosis Links Page as already suggested by Nick.
different colours made of tears

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Postby Magna Carter » Wed Dec 28, 2005 1:12 am

Serious Osmosis will result in thousands of blisters, far too much to hide with paint, or in some cases, several extremely large blisters (the size of dinner plates), so again, v hard to cover up......

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Postby DaveS » Tue Jan 31, 2006 8:56 pm

If fresh water has been sitting inside for some time you can expect to get a high reading from a moisture meter. I was caught by this when selling my last boat. A cockpit locker filled with rainwater over the winter which then overflowed into the hull, resulting in a surveyor's "high mosture reading" observation which in turn was translated as "hull riddled with osmosis". Complete bllx but it certainly dropped the price I got. :cry:

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Postby claymore » Wed Feb 01, 2006 5:36 pm

I used to run a sailing centre on a reservoir where the water catchment area was very peaty.
We used GRP Wayfarers as the bulk carriers and I bought 3 from Porters when he started building them. They all had to go back after a season on their moorings as huge blisters had started appearing. A surveyors report commented that the high Ph content in the water had almost certainly contributed to the osmosis.


Postby Anonymous » Sat Mar 25, 2006 5:00 am

I think you are right guys! :)

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