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post #11 of 33 Old 03-25-2014
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Re: Osmosis conspiracy theory

AFAIK, osmosis in boats is generally caused by a poor gel coat application prior to laying up the glass fibre. The glass follicles penetrate a too-thin gel coat and then, when submerged in water, allow water to migrate up the follicles into the lay-up and cause a blister.

This is apparently why boats that float for extended periods of time in fresh water generally are more susceptible to osmosis - sea water has a higher density and thus doesn't migrate up the follicle as easily.

But then you all knew that . . . . right?


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post #12 of 33 Old 03-25-2014
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Re: Osmosis conspiracy theory

Quote:
Originally Posted by Omatako View Post
AFAIK, osmosis in boats is generally caused by a poor gel coat application prior to laying up the glass fibre. The glass follicles penetrate a too-thin gel coat and then, when submerged in water, allow water to migrate up the follicles into the lay-up and cause a blister.

This is apparently why boats that float for extended periods of time in fresh water generally are more susceptible to osmosis - sea water has a higher density and thus doesn't migrate up the follicle as easily.

But then you all knew that . . . . right?
Actually I thought it was just a bad case of Polyestermite infestation.

Once one of them dreaded beasties gets into the mat through a pinhole in the gelcoat, they can live for years just chewing away at the hull from the inside out. Their piss is highly acidic and it's that what comes out of the blisters when you pop 'em.. You can see it clearly in this pic of a Polyestermite burrow from MaineSail's post:

Quote:
Originally Posted by Maine Sail View Post
If you're a first-time boat owner, it's really REALLY IMPORTANT that you pull the boat out regularly and check the hull thoroughly with a magnifying glass for any of the tiny tell-tale entry points, 'cause if you get a few more holes like the one in Maine's pic, you could arrive at the boat one day only to find it sunk at it's moorings.

That's why I own a timber boat - I'll never need to worry about Polyestermite!




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Last edited by Classic30; 03-25-2014 at 08:15 PM.
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post #13 of 33 Old 03-25-2014
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Re: Osmosis conspiracy theory

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A hammer did not cause this crappy lay up thought its likely a hung-over or stoned laminator did..
So your saying it wasn't a hammer but rather getting hammered that was the potential cause. Well, the OP was almost right than...

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post #14 of 33 Old 03-26-2014
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Re: Osmosis conspiracy theory

Quote:
Originally Posted by Omatako View Post
AFAIK, osmosis in boats is generally caused by a poor gel coat application prior to laying up the glass fibre. The glass follicles penetrate a too-thin gel coat and then, when submerged in water, allow water to migrate up the follicles into the lay-up and cause a blister.

This is apparently why boats that float for extended periods of time in fresh water generally are more susceptible to osmosis - sea water has a higher density and thus doesn't migrate up the follicle as easily.

But then you all knew that . . . . right?
Nope, not at all.

Purpose of gelcoat is to bring a nice color, to even out the not always even other layers and to establish a layer between the layers with glass fibres (ie grp) and the outside. The plastic in gelcoat is usually the same as in the grp, main diff is the addition of color (pigments). Usually, gelcoat is not good for protection against water - epoxi is superior to gelcoat, as an example.

The osmosis process is fairly complex, se eg
(which is declared as " factual accuracy is disputed", a sign of complexity). In sailing boats, some different processes have been identified to cause osmosis - not sufficiently cured grp is one, the mat powder, plastic quality and so on.

Aah, and then gelcoat thickness: should not be too thick either, then there wil be cracks in it as there is no reinforcement (as glass fibre). Not unusual that on inside of the boat where gelcoat has been painted on, as topcoat, cracks develops over time, as these layers easily becomes too thick.

/J
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post #15 of 33 Old 03-26-2014
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Re: Osmosis conspiracy theory

I believe the Latin for that critter is "polyester lemnoria" a relative of the well known pin worm. Not closely related to the dreaded toredo navalis which is actually a mollusc. We even have a hybrid here in BC, the toredo silicosis ,which was the scourge of ferro cement hulls back in the '70 's .A particularly bad infestation can be seen on the sandstone cliffs on the upper Gulf Islands.
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post #16 of 33 Old 03-26-2014
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Re: Osmosis conspiracy theory

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. . . . . . and to establish a layer between the layers with glass fibres (ie grp) and the outside. . . . .
Yes, I agree

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Usually, gelcoat is not good for protection against water . . .
It's a pity that the people who have built the millions of gel-coated sailing boats that exist today appear not to have known that. It is true though to say that for every blistered hull there are a huge number of unaffected ones so maybe they all just got lucky.

I also find it interesting that nowhere in the Wiki article does it mention yachts, glass fibre, salt water or anything else to do with the subject matter. Oh, maybe that's because the word osmosis may have more than one connotation. Wiki searches can be and often are misleading.

But then you do sound like an expert so I'll bow to your superior knowledge.


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post #17 of 33 Old 03-26-2014
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Re: Osmosis conspiracy theory

So a short form definition of Osmosis is that unequal pressures on either side of a semi-permeable membrane (polyester is hygroscopic) will difuse and equalize ........... wouldn't that sink your boat ?

Osmosis Testing on Boats

The hysterical laughter you hear as you drive a way in your"new" boat ..... is the seller.
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post #18 of 33 Old 03-26-2014
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Re: Osmosis conspiracy theory

I find it interesting that most of those who are disputing your theory are either surveyors or the repair yards who would benefit from the "work" of the surveyors. I think you're on to something. Just be careful...you may see (but won't hear) a black helicopter with BoatPoker and MaineSail aboard in your rear view mirror if you keep this up.
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post #19 of 33 Old 03-26-2014
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Re: Osmosis conspiracy theory

now guys...
good point jimgo

here is my final take for the op

1. how deep and what is your hull construction?
2. if cored you are in more danger than if solid, yes even if it was crappy and overly layed up glass and excessive resin back in the 60s and early 70s...they do fair better since they are so thick.
3. are the bubbles in the gelcoat(extrenal layer) or are they deeper than say 1mm skin


if the later its more of an issue but still liveable with and fixeable.

if the former I dont even bother

I have had 3 or so boats with minor blistering...most blisters were in the dime size or rubber pencil tip size or slightly smaller I had some with about a dolar pancake size and what I simply did was scrape off the gelcoat or bubble and apply some nice mix of thickened resin, sand and then off to the bottom paint

simple and it lasts btw...if next haulout more pop up which normally happens just do the same...

if you do want to eliminate all SURFACE pox you can barrier coat...simple but so expensive these days and not worth it for the majority if used boats out there especially in the median cruiser size range...30-35feet

its unfortunate we are in the dinosaur days of yards letting you do your work, cause I beleive this has become more of an INFLUENCER of potential buyer turning down otherwise simple bottom jobs on potential boats they are looking at.

last place I worked on a boat was gravelles in california, and apparently they no longer let you do any bottom work which is a shame...

I did a nice bottom job, strut realignment with new cutlass bearing and engine realignment...in a a week.

I did just this last year...

in any case blistering or osmosis threads, like oil type threads or inboard or outboard threads always seem to be extremist and get off track very easily and bring out very high and mighty opinions both good and bad.

so lets all be happy

jajajaja

Merit 25 sold...Islander 36 still afloat? who knows...Im still in Columbus, and back...I think...jajajaja!!!!
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post #20 of 33 Old 03-26-2014
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Re: Osmosis conspiracy theory

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The hysterical laughter you hear as you drive a way in your"new" boat ..... is the seller.
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