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Old 12-11-2014, 10:57 AM   #1
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Red face Bottom of Mattress Wet!

No I did not pee in the bed.

As livaboards we found a livaboard issue the other day. Condensation on the bottom of our mattress. It is made of high density foam. We got everything cleaned up and asking how can we prevent this?

A friend of ours is telling us that there is a kit (?) to put under the mattress that creates an air cavity between the mattress and the bed frame. True? If so where can I get one?
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Old 12-11-2014, 11:10 AM   #2
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The water condenses at the freezing point .

A few solutions work , some sort of pad (think super sizes scotch brite pad) that will allow warm cabin air under works fine.

So does drilling the bed and allowing more cabin heater air under the bed.

What works is basically any method you can work to have the bottom of the mattress stay above freezing.

Some times simply lifting/airing the mattress daily will get rid of enough moisture that it wont ice at night.
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Old 12-11-2014, 11:17 AM   #3
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It's called HyperVent. I've used it for years and it really does work. Sold at Fisheries Supply for $10/ft. (39Wx3/4" thick).
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Old 12-11-2014, 11:30 AM   #4
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Yup- good stuff!
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Old 12-11-2014, 11:55 AM   #5
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I knew I could get the right answers here at TF. Thanks
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Old 12-11-2014, 12:20 PM   #6
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I tried hypervent but it didn't solve the problem. The center of the mattress still got wet and mildewed.

So I bought the Froli Sleep System (Froli Sleep Systems by Nickle Atlantic, LLC). The bed is more comfortable AND the bottom of the mattress stays totally dry. More expensive than hyper vent, but more effective too.

The old hypervent is in good condition and still in the back of my car, so if anyone wants it and can pick it up, let me know! Free to a good home...
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Old 12-11-2014, 12:28 PM   #7
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We sold the Froli system for a couple of years before we went cruising. It's the best. The only place you can get it now is from Nickle Atlantic. The woman you deal with is a little cranky but you will get an awesome product.
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Old 12-11-2014, 12:42 PM   #8
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We use HyperVent under our main berth. Solved the problem perfectly and is still doing so some 16 years later.
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Old 12-11-2014, 12:52 PM   #9
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Quote:
Originally Posted by FF View Post
The water condenses at the freezing point .

A few solutions work , some sort of pad (think super sizes scotch brite pad) that will allow warm cabin air under works fine.

So does drilling the bed and allowing more cabin heater air under the bed.

What works is basically any method you can work to have the bottom of the mattress stay above freezing.

Some times simply lifting/airing the mattress daily will get rid of enough moisture that it wont ice at night.
Condensation occurs at dew point.
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Old 12-11-2014, 01:14 PM   #10
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Quote:
Originally Posted by boatpoker View Post
Condensation occurs at dew point.

That's what I thought, the saturation point depends on the temp/humidity

We get a lot of dew (condensation) here in Florida way above the freezing point like the mid 60's and up. No ice scrapers needed just wipers.

Fog forms well above freezing and it is complete condensation (super saturation)
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Old 12-11-2014, 03:30 PM   #11
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I went to the home improvement store and got several pieces of roof ridge vents. They are usually about 1" thick by 12"x 48". You can drill a few extra holes in each panel.

Something like this: Air Vent: Hip Ridge Vent

A lot cheaper than $10 per sq ft and work great.
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Old 12-11-2014, 03:37 PM   #12
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Condensation occurs at the dew point

Quote:
Originally Posted by SCOTTEDAVIS View Post
That's what I thought, the saturation point depends on the temp/humidity

We get a lot of dew (condensation) here in Florida way above the freezing point like the mid 60's and up. No ice scrapers needed just wipers.

Fog forms well above freezing and it is complete condensation (super saturation)
Don't mean to be picky... just trying to straighten out some technical terms that are sometimes confusing.

Condensation forms at what is known as the DEW POINT (YES - this is also saturation point for that temp - super saturation is something else again and probably outside the scope of this conversation).
Dew point is a function of the moisture content in the air - otherwise know as ABSOLUTE HUMIDITY LEVEL...
Not to be confused w/ RELATIVE HUMIDITY which as a combination of how much water is present (ABSOLUTE HUMIDITY) and the AIR TEMP (which affects how much moisture the air can hold at that (and only that) temp.
So - relative Hum changes as the air temp changes - absolute Hum (and Dew Pt) for practical purposes does not change w/ temp.

When the air cools to the dew point you get saturation & condensation.

The above - and a whole lot more - is covered in the US Power Squadron Weather Course - which is now available online as well as live through local Sail & Power Squadrons. See USPS.ORG if interested.
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Old 12-11-2014, 04:35 PM   #13
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Quote:
Originally Posted by Bacchus View Post
Don't mean to be picky... just trying to straighten out some technical terms that are sometimes confusing.

Condensation forms at what is known as the DEW POINT (YES - this is also saturation point for that temp - super saturation is something else again and probably outside the scope of this conversation).
Dew point is a function of the moisture content in the air - otherwise know as ABSOLUTE HUMIDITY LEVEL...
Not to be confused w/ RELATIVE HUMIDITY which as a combination of how much water is present (ABSOLUTE HUMIDITY) and the AIR TEMP (which affects how much moisture the air can hold at that (and only that) temp.
So - relative Hum changes as the air temp changes - absolute Hum (and Dew Pt) for practical purposes does not change w/ temp.

When the air cools to the dew point you get saturation & condensation.

The above - and a whole lot more - is covered in the US Power Squadron Weather Course - which is now available online as well as live through local Sail & Power Squadrons. See USPS.ORG if interested.
Thanks, I have a good working knowledge about the subject from my USCG, Private Pilot, and Sky Warn Weather Reporters classes.

Dew point does indeed change with temperature, when the temperature goes below the dew point water will condense out of the air and the air will have less humidity in it. Cold air can not hold as much water vapor as warm air.

The dew point is the saturation temperature for water in air.

The dew point is associated with relative humidity (RH). High RH means that the dew point is closer to the current air temperature.

When the dew point and the air temperature are the same look out for fog. Ask any pilot when flight planning about the importance of dew point air temp. spread.

The point was water does not condense at the freezing point as was stated as a fact.

The term supersaturaion should not have been used by me as this is rare outside of a lab due to nucleation particles present in the air, cloud/fog formation will occur before supersaturation is reached. Sorry
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Old 12-11-2014, 04:41 PM   #14
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We used the DriDeck (?) tiles sold at WM. Worked for us for six years on our sailboat.


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Old 12-11-2014, 06:46 PM   #15
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FYI, You can also get the mesh style from Columbia Marine Exchange in PDX. We have it under our mattrest and it has kept it dry & mildew free.
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Old 12-11-2014, 09:29 PM   #16
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So the bottom of your mattresses are freezing! I knew there was a reason i lived in the south.
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Old 12-11-2014, 11:08 PM   #17
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Our aft cabin has a water tank under the bed. the cool water combined with out body heat makes for some condensation, so I put a layer of hard insulation across the top of the tank. It really helps a lot.
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Old 12-12-2014, 05:40 AM   #18
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We use the Froli system and it solved the problem we had with condensation.
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Old 12-12-2014, 07:01 AM   #19
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Living aboard in NYC the dew point was easily reached and the water produced would freeze to the unvented , unheated sail locker under the bed.

An electric sheet was not enough heat to drive the dew point out if the heavy foam mattress , but lifting to vent when un occupied did the trick.

A fitted sheet under the mattress aided in lifting with out harming the frozen foam.

When folks decide they want to liveaboard , there are many interesting challenges , this is only one.
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Old 12-12-2014, 10:35 AM   #20
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Dri-Dek tiles worked for us... a really easy fix.
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