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Heres my conspiracy theory on the cause of osmotic blisters. You take two like boats same vintage and location, one is single owner one has had many owners. One has blisters one doesn't. Its the surveyor and his damn ball-peen hammer hammering into a fiberglass hull At it takes is a small void in the gelcoat to expose a single mat strand and your off. Ive told this to several of my surveyor friends and they scoff at me yet not a single one of them can source the trigger point. Its 2014, there has got to be something more sophisticated than a frigging hammer. In my book Boatyard Pirates I have an entire chapter dedicated to this.

I'm just saying... :)
 

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I once asked a surveyor to "Lighten up with the hammer will ya ? You're LOOKING for voids, not trying to make 'em", ok for the hull, but he was a little overboard on the cabin top.
 

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Since most boats need a survey every 5 years or so for insurance purposes, your theory doesn't really hold water very well. Though my boat has only been sold 3 times, it has probably had at least 6 surveys that had no relation to these sales.
It is the quality of construction and the knowledge of the materials at the time of construction, that makes all the difference. You can pretty much guarantee osmosis on certain boats, by manufacturer, and be quite comfortable that it won't be a problem on others.
As for tapping on a hull with a hammer; if your hull can't take that, then you'd better never leave your marina without some form of deflection unit on your bow, because one can always run into something floating in the water that would certainly put more pressure on a hull than a surveyor's tiny little hammer. Just hitting a beer bottle at 6 to 8 knots could be a pretty good little hit, never mind a log or good size plank.
"Osmosis conspiracy theory" busted!
 

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Heres my conspiracy theory on the cause of osmotic blisters. You take two like boats same vintage and location, one is single owner one has had many owners. One has blisters one doesn't. Its the surveyor and his damn ball-peen hammer hammering into a fiberglass hull At it takes is a small void in the gelcoat to expose a single mat strand and your off. Ive told this to several of my surveyor friends and they scoff at me yet not a single one of them can source the trigger point. Its 2014, there has got to be something more sophisticated than a frigging hammer. In my book Boatyard Pirates I have an entire chapter dedicated to this.

I'm just saying... :)
The problem would be that I have seen lots of one owner, un-surveyed boats that have had blisters.... Not all insurance companies require surveys so its kind of tough to explain that one being due to a hammer when a hammer never hit the hull.

For example our old neighbors bought a Tartan 27 brand new and kept it for well over 20 years. The hull suffered severe blistering and was stripped, dried and fixed back in the late 80's. Issue never occurred again. That boat had never been surveyed yet was riddled with pox..

Other boats I know of that have been sold often and have been surveyed sometimes every three years have no blisters even after 30+ years and multiple surveys.... . Some of these customers bought the boats brand new and then had them for 20-25 years with multiple surveys, perhaps thousands of hits, and no blisters....

here's a customers boat that was NEVER surveyed..

A hammer did not cause this crappy lay up thought its likely a hung-over or stoned laminator did..:)


When a hammer has been found to be the cause of crappy lay-up please let us know..;);)

These blisters were all popped by hand with an awl.. Agian this boat was never surveyed... Hammer conspiracy fail.....:D
 

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I do use a HARD plastic one :) and it tells me plenty


The only blister that ever showed up on the Cal 29 was inside the sterntube and did in fact come close to sinking the boat

The tube was some piss poor hand work FULL of air bubbles
 

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I do use a HARD plastic one :) and it tells me plenty

The only blister that ever showed up on the Cal 29 was inside the sterntube and did in fact come close to sinking the boat

The tube was some piss poor hand work FULL of air bubbles
Clearly someone must have yanked the shaft and hit the stern tube with a hammer to cause that....:D:D;)
 

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The fabulous original workmanship :( NOT in this ONE section of the hull that i would guess was done after it was pulled from the mold ?



Thats one of the tiny ones



A tom custom tube remover



with absolutely no issues in the rest of the layup





The original aliment job of the strut/tube/motor was so screwed it was just as well anyway as NOW everything is correct
 

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I once asked a surveyor to "Lighten up with the hammer will ya ? You're LOOKING for voids, not trying to make 'em", ok for the hull, but he was a little overboard on the cabin top.
dude same thing here!!!!!!

I had just finished painting the bottom on an old boat and the new owner was very happy with the job only to have the surveyor ***** and pry a big ******** on a quarter sized bubble I told him thats the first and last one you do...you dont need to open them you can tell if they have water or not

anywhoo

too funny:)
 

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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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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:

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. :eek: :eek:

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

:p ;) :D
 

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

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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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
 

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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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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
 
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