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Jeanneau Attalia
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Discussion Starter · #1 ·
Does anybody know what this is? I discovered it at the end of one summer when I was away and kept the boat on the hard, covered with a tarp. Could it have been the heat, friction? It looks like someone used something to wipe the hull and it blistered. Its about 8 sq ft, all above the water line. I've been sailing her since. It was a one time "event", it has not spread and the boat is now in the Caribbean for about a year and no additional effect. Next question, to fix it ? :
 

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Sailor
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Was it shrink wrapped or any type of heat gun used? Maybe sat in a puddle of water? Either way, it could be blisters like on the bottom from water, perhaps heat.


Mandolin, Bayfield 36 out of Rock Creek, Chesapeake Bay.

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Those are blisters formed from the heat shrink. You had sweat, and or moisture(rain) that got trapped against the hull. The heat of the sun opened the pores of the gel coat, while making the water turn to vapor, which then entered the gel coat! When I had my boat surveyed on purchase there were a few mild ones that the surveyor found and explained why it happened. He told me to put foam pipe insulation between the hull and cover and it would stop that from happening again.
 

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Dirt Free
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Those are blisters formed from the heat shrink. You had sweat, and or moisture(rain) that got trapped against the hull. The heat of the sun opened the pores of the gel coat, while making the water turn to vapor, which then entered the gel coat! When I had my boat surveyed on purchase there were a few mild ones that the surveyor found and explained why it happened. He told me to put foam pipe insulation between the hull and cover and it would stop that from happening again.
I agree. Whether a tarp or shrink wrap any material tight against the hull can cause this in hot humid weather..... seen it many times.
 

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That's an area that had fresh water trapped against the hull. You see the same thing when boats are put in fresh water with no paint or barrier coat. Gelcoat is more water proof than FRP without it. Your boat is 31 years old making your gel very pouris allowing moisture to enter. when the sun hit it the water trying to evaporate causes those type blisters. Only remedy is to remove gelcoat & paint.
 

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There is no need to remove the gel coat. Just let it air dry for a few months and the blisters will evaporate. It looks ugly while it happens, and you likely will have some that will need repair, but it isn't indicative of a major problem, except with how the boat was stored.
 

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Jeanneau Attalia
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384 Posts
Discussion Starter · #7 ·
Thanks folks!
Sounds about right. It wasn't heat shrink but "one " piece of that blue tarp which I needed to extend the (canvas) tarp so I used one of those blue ones. Big mistake. Anyhow will haul out probably in July so would like to fix it. Essentially sand it down and...
 
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