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Old 15-03-2014, 09:40   #16
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Re: Osmosis Question

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But the blister did not just appear with out cause. My guess is the resin did something to push out a blister. You can get a decent water egress profile by grinding into the finish layer. Not necessary to core the hull.
Most blisters appear in the gelcoat and are generally round and somewhere around 1/4" diameter maximum. If the blister is slightly elongated, this indicates that the issues is in the chopped strand of the skinout mat. Once the blister approaches 1/2" diameter this strongly suggests hydrolytic blistering and a puncture with an ice pick will produce the tell tale brown fluid.

The blisters that release clear water are a cosmetic issue, the brown liquid is what you have to watch for as it indicates decay of the resin through hydrolysis. The extent and type of 98% of the these issues can be determined with an ice pick.

You might want to take a look at Moisture Meter Mythology and Osmosis Testing.
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Old 15-03-2014, 09:45   #17
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Re: Osmosis Question

Can you have hydrolytic reaction and no blister?


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Old 15-03-2014, 09:51   #18
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Re: Osmosis Question

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Can you have hydrolytic reaction and no blister?


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In it's early stages I guess it could. When the water molecules combine with the resin molecules the combination forms a larger molecule that will eventually show up as a blister.
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Old 15-03-2014, 10:15   #19
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Re: Osmosis Question

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In it's early stages I guess it could. When the water molecules combine with the resin molecules the combination forms a larger molecule that will eventually show up as a blister.



I've seen severe hydrolysis with no blistering several times.
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Old 15-03-2014, 10:17   #20
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Re: Osmosis Question

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I've seen severe hydrolysis with no blistering several times.
I have not seen that but I wouldn't argue the point. I would think there would be some visible indication of unfairness. Something of this nature would, I'm sure be easily determinable with my brass hammer.
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Old 15-03-2014, 11:49   #21
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Re: Osmosis Question

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I have not seen that but I wouldn't argue the point. I would think there would be some visible indication of unfairness. Something of this nature would, I'm sure be easily determinable with my brass hammer.



Definitely (though I prefer a nylon hammer).
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Old 15-03-2014, 13:00   #22
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Re: Osmosis Question

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Definitely (though I prefer a nylon hammer).
My favourite is the brass plane hammer from Leigh Valley Tools. One end of the head has a recess for a replaceable hardwood plug (white oak at the moment).
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Old 15-03-2014, 15:06   #23
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Re: Osmosis Question

I believe that osmosis is a very precise describtion of a specific proces in the layers of the hulll. But I have heard a lot of different definitions from people all around about this subject, so you got a point there "boatpoker"
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Old 15-03-2014, 22:47   #24
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Re: Osmosis Question

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My favourite is the brass plane hammer from Leigh Valley Tools. One end of the head has a recess for a replaceable hardwood plug (white oak at the moment).



Nice. I prefer a very small hard plastic ball peen hammer, made for jewelers. They are hard to find. The ball peen end lets you tap out radii and find every teeny factory void in them. A flat head straddles the void instead of popping it. I prefer hard plastic to wood or metal because I think "hammer sounding" is a misnomer. It's not just about sound, it's about bounce and "feel". A plastic head has more bounce. I feel like its a more sensitive instrument as a result. Mine is called "the Money Hammer", as it makes us money. It has discovered millions worth of damage in its time.
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Old 16-03-2014, 03:41   #25
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Re: Osmosis Question

You're right the feel/bounce is just as important as the sound. It's hard to tell in the photo but the small hammer has brass tip on one end and a hard white plastic tip on the other. I tend to to use the small hammer on topsides and decks and the larger hammer on bottoms. I've tried a lot of different things over the years including a golf ball drilled for a dowel. It comes down to your own ear and feel and what you get used to. Most people I know use that amber coloured plastic and that just does not work for me.
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Old 16-03-2014, 10:11   #26
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Re: Osmosis Question

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You're right the feel/bounce is just as important as the sound. It's hard to tell in the photo but the small hammer has brass tip on one end and a hard white plastic tip on the other. I tend to to use the small hammer on topsides and decks and the larger hammer on bottoms. I've tried a lot of different things over the years including a golf ball drilled for a dowel. It comes down to your own ear and feel and what you get used to. Most people I know use that amber coloured plastic and that just does not work for me.



Agreed. Don't get me wrong, brass has its place (hulls). And it definitely has a lot to do with personal preference and what you are used to. Do you also use a peen or conical head for finding voids, or are you trying not to open those for the sake of your client? I don't have to be nice about it, I try to find every single flaw. It's more work for us, and reflects well in the quality of our work. No voids found after the fact.
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Old 16-03-2014, 12:08   #27
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Re: Osmosis Question

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Agreed. Don't get me wrong, brass has its place (hulls). And it definitely has a lot to do with personal preference and what you are used to. Do you also use a peen or conical head for finding voids, or are you trying not to open those for the sake of your client? I don't have to be nice about it, I try to find every single flaw. It's more work for us, and reflects well in the quality of our work. No voids found after the fact.
I'm in a different position than you. I am working for the buyer. If I do any damage and the deal does not proceed, the seller is coming after me for cost of repair.

I once cut a small u-shaped hole in shrink wrap to get the HIN and another to get the license number. The deal fell through because of issues I found on the boat and the owner came after me in small claims court for $600 in shrink wrap.

Yes ... he won.
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Old 16-03-2014, 12:26   #28
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Re: Osmosis Question

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I'm in a different position than you. I am working for the buyer. If I do any damage and the deal does not proceed, the seller is coming after me for cost of repair.

I once cut a small u-shaped hole in shrink wrap to get the HIN and another to get the license number. The deal fell through because of issues I found on the boat and the owner came after me in small claims court for $600 in shrink wrap.

Yes ... he won.




I hate needlessly litigious folk with a passion.



I also like a peen because it lets you hammer sound in a fillet.
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