The Dreaded Lurgy

manimbored

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I'm posting this on behaf of my less internet savvy Dad.

His boat (Trapper 501) is out of the water, going through a minor refit, (new prop, stripping and cleaning the engine, replacing windows, stopcocks and stuff)

My dad went down to it today, and found it was full of water. Not sure where its getting in, the port aft window is out, getting replaced, but thats covered by a tarpaulin. One of the trailers supposts was blocking the outlet for the bilge pump, so thats why it wasnt draining.

Anyway, problem solved, and after about 15 minutes the bilge pump finished. Dad went down the ladders to get the new window, and seen the hull covered in "millions of tiny blisters) about the size of a pinhead, some slightly bigger. This was only on the 'white bit' of the hull, i.e. between the waterline and the gunwhales. There was none of this at all until now, so it has surfaced in the past couple of weeks since we were last down.

Everyone is at a loss as to how this happened. Dad burst one of the larger blisters and there was water behind it. I am lead to believe, that for 'normal' osmosis, the water behind a blister smells vinagary, well these didn't, if thats any help. The boat sails in freshwater now, but was in the sea up until May 2006.

Has anyone any idea whay could have caused this, or how best to fix it? The weird thing is that there is none below the waterline. Although it was flooded inside, it was only flooded up to around the waterline, and not for any significant length of time.

It seems to me like a case of the dreaded lurgy.
 
FWIW.
If the topsides are painted it could be that there was too much humidity on the hull when the paint was put on.
Does not sound like osmotic blistering. (Well, technically one could say that it is a form of osmosis but definitely not the kind that we dread)
 
Agree with with Puff, its moisture under the coating, just keep her well ventilated and don't pop anymore or you will let more moisture in. you may see them flatten after a good summer.

A coat of high build epoxy primer on the original gel coat helps prevent this common problem.

Avagoodweekend......
 
[ QUOTE ]
FWIW.
If the topsides are painted it could be that there was too much humidity on the hull when the paint was put on.
Does not sound like osmotic blistering. (Well, technically one could say that it is a form of osmosis but definitely not the kind that we dread)

[/ QUOTE ]

The topsides havent been painted since new.

[ QUOTE ]
there is a chap with a similar prob here
http://www.ybw.com/forums/showflat.php/Cat/0/Number/1719552/an/0/page/0#1719552

[/ QUOTE ]

Yea that chap would be my "less internet savvy" Father /forums/images/graemlins/grin.gif
 
Must be the dreaded Paddy pox - only occurs on the dry bits above water! /forums/images/graemlins/grin.gif Sorry - warped sense of humour.

You say [ QUOTE ]
The topsides havent been painted since new.

[/ QUOTE ]. What is happening must be some sort of osmosis problem - the blisters are evidence that pressure is building underneath the surface layer whether gel or paint. Normal osmosis blisters under gel smell of acetic acid because that is a breakdown product of the reaction that is taking place.. The absence of the smell plus the location of the blisters well clear of any immersion area suggest that the problem isnt normal osmosis but some paint problem - which brings us round in a circle.

When your father pricked the blister, how thick was the layer he had to break through and what was underneath? Thin layer and white ngel underneath = paint. Thick layer and laminate underneath = gel.

Suggest you phone Nigel Clegg who is both very helpful and knowledgeable http://www.passionforpaint.co.uk/
 
When you say haven't been painted since new, that doesn't actually mean do not have a coating on.

Just clarify. Are the topsides gelcoat or a decorative coating. Either way sounds like a drying out and coating are needed now. I don't usually subscribe to treating osmosis, but when it's on the topsides (whatever the cause) it's worth being decorative.
 
In the late 1980s, our Trapper 501 suffered from ' wicking' where the fibreglass fibres had not been fully immersed in resin and protruded into the gelcoat. We had Tony Statton- Bevan carry out the survey. I believe he was the most expert surveyor on osmosis etc. at that time. The treatment was the same as normal osmosis, remove gelcoat, dry out and recoat. Treatments and opinion seem to have changed since then.
 
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