Hull Sweating

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
fillman
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Joined: Tue Aug 21, 2018 6:18 pm

Hull Sweating

Postby fillman » Sun Oct 07, 2018 9:08 pm

Is hull sweating common?

I was sanding in preparation for applying a primer paint. I noticed the bottom of the hull was sweating. It was a very humid day after a cool down. I never noticed hull sweating before when working on the hull on several summer humid days.

Masbama
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Joined: Thu Oct 15, 2015 8:33 pm
Location: Mobile, Al

Re: Hull Sweating

Postby Masbama » Mon Oct 08, 2018 9:18 am

It may just be condensation.

ConB
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Joined: Fri Oct 09, 2015 2:52 pm
Location: Suttons Bay, MI

Re: Hull Sweating

Postby ConB » Mon Oct 08, 2018 4:01 pm

I've seen condensation on my Whaler hulls numerous times.

You want to paint on a day with less humidity.

Con
!987 Outrage 18 / 1987 150 hp Johnson & 1969 13 / 30hp Johnson tiller

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Dutchman
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Re: Hull Sweating

Postby Dutchman » Wed Oct 10, 2018 11:46 am

Even if you paint on a less humid day during the day or afternoon watch out for the night time drying as the cooler temps wreck havoc with the paint or varnish. The result is not what you expect the next morning. Don't ask me how I know.
EJO
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jimh
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Re: Hull Sweating

Postby jimh » Thu Oct 11, 2018 11:53 am

fillman wrote:Is hull sweating common?


If you mean. "Does water from the inside a Boston Whaler Unibond hull suddenly pass through the gel coat resin layer and appear all over and rather uniformly on the outside of the hull?" then, no, that is not a common occurrence.

The gel coat resin layer is mostly a non-permeable layer. It is possible with continuous and prolonged immersion in water that the gel coat layer might absorb some water. This is the behavior that leads to the condition of the gel coat known as osmotic blistering.

With Boston Whaler boats, osmotic blistering has not been a problem that has been reported frequently. Note that Boston Whaler recommended in their owner's literature that the portion of a hull that was below the water line on any boat that would remain in the water for more than few days be top coated with a two-part epoxy paint as a barrier coat. Such a barrier coat would enhance the characteristic of the gel coat layer to remain impermeable to water.

Generally if a hull has any entrapped water, the only external visual manifestation of the entrapped water would occur at some place where the gel coat layer was damaged, and if the damage was at a low point so water flowed their by gravity, water would be seen seeping or weeping from the hull.

dtmackey
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Joined: Thu Sep 28, 2017 9:29 pm

Re: Hull Sweating

Postby dtmackey » Thu Oct 11, 2018 10:43 pm

Happens a lot in this area when we have cold nights and then a warm humid day. The hull retains the cold and the moisture in the humid air condenses on the hull. Spring and fall seems to be the times when it is the most common since the temps from night to day swing quite a bit.

D-