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Old 12-12-2014, 11:00 AM   #21
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As I get older or invite the grandkids, a rubber sheet helps the mattress from getting wet

On a more serious note, we have found that heavier guests sweat a lot more when sleeping and even with the air vent stuff under the mattress, after a few days moisture can appear. Jenny Craig or Slim Fast maybe??
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Old 12-13-2014, 01:01 AM   #22
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Froli works great in getting rid of condensation issues. As an added bonus it also acts somewhat as a box-spring under the mattress, improving comfort. Especially if you have a typical boat mattress...
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Old 12-13-2014, 04:59 AM   #23
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Look into getting air flow out of the space below the mattress. The PO put a fan and piping system in the space under the mattress. It's called a circumvent. I've got the literature on it but cannot find a reference for it on the web. It works quite well. He also put that thick "scotch brite meshy thingy" under the mattress as well.


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Old 12-13-2014, 05:51 AM   #24
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Especially if you have a typical boat mattress...

Any mattress (or seat cushion ) has a hard job plopped on a slab of plywood.
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Old 12-13-2014, 09:13 AM   #25
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Hypervent or something similar is on my list of "Things to do" -- Seaweed's insulation is nonexistent.

What I did in the bilge locker was take the 1/4" foam that came on my solar panels and placed it along the hull. That was enough for the locker under my bunk and the two under the dinette seats.

I should have done the bunk first but it was summer time then and now... well, raising the mattress, with assorted winter gear (electric blanket, etc.) is difficult.

It seems like there ought to be a non-marine source for some sort of scrubby (like hypervent) for lots less money.
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Old 12-13-2014, 04:06 PM   #26
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Quote:
Originally Posted by janice142 View Post

It seems like there ought to be a non-marine source for some sort of scrubby (like hypervent) for lots less money.
Tuff-N-Nuff Rock Shield by Greenstreak protects pipelines

I have no idea of cost and availability. It would be the cats meow. (cats don't like being wet)
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Old 12-16-2014, 04:04 PM   #27
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I've just searched through on the PO's documents on how he attacked this problem. Obviously "boat moisture" is a concern for most of us at one time or another during the boating year. In the PNW, it seems worst in the October-November months, but can "flare-up" during the winter when a cold-snap is followed by a pineapple express.

The PO was on a mission against boat moisture and placed “Hypervent" under the mattress and installed a "Circumvent" which is a stainless steel air exchanger. A web search reveals nothing about the device. I have several sheets of text, and a pamphlet referencing Circumvent International (a division of Nanaimo Humidity Control, the phone number of which is not in service!), a couple of other "not in service" phone numbers and a now defunct website: dry-out.com. "Circumvent" essentially consists of a DC fan, controlled by a humidistat. The unit is installed as low as possible in the bilge. When running, air is drawn from the bilge and piped outside the boat. The negative pressure created draws air back into the boat. The unit works when colder air from the outside, is warmed and the humidity drops (humidity is a function of temperature) and that air "dries out" the interior structures of the boat, and is then pumped outside the boat. Mattresses, clothing and blankets are moisture traps and these are dried out over time.

Clearly the system works best when there is a humidity differential between the inside and outside air: Cold outside air holds less water than warm inside air as the chart below shows. Overall, I think the "thing" works, and draws 1.4 amps when the fan is running, which over 24 hours when on the hook is 34 ah, so the draw when on the hook is important to consider. However, it is probably best to turn the unit off when the winter pineapple express rolls through as the outside air contains a higher humidity and replacing the low humidity inside air with outside air of higher humidity results in condensation in the bilge area.

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Old 12-16-2014, 04:37 PM   #28
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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.
That is exactly my setup.
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Old 12-16-2014, 04:39 PM   #29
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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.
Interesting idea....
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Old 12-16-2014, 05:27 PM   #30
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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.
:thumbs:

Actually, Bacchus is correct. Dew point is a measure of absolute humidity.

And the advice is correct.

A minor points, super saturation occurs almost in ALL clouds. Otherwise aircraft would pretty much never ice.
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Old 12-16-2014, 06:45 PM   #31
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On another forum someone suggested using the wooden lattice sets sold in 4'x8' sections at Lowes or HD. The wooden ones not the plastic as the wood pieces are laid in crossing pattern and will have spaces for better airflow. We have never had the problem on our boats but I think the wood lattice should work.

Shop Spruce Traditional Wood Lattice (Common: 0.5-in x 4-ft x 8-ft; Actual: 0.5-in x 48-in x 96-in) at Lowes.com
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Old 12-17-2014, 03:51 PM   #32
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Another good idea!
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Old 01-05-2015, 11:05 AM   #33
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Installed the much recommended HyperVent under mattresses last weekend. Due to its obvious value, I also now fully recommend it.

Order through:

Website - HyperVent Marine - Putting An End To Condensation

Email - 'hypervent_info@comcast.net'

Phone - 360 657 5503

Ask for Rex. Tell him Art with Tollycraft tri cabin sent ya. He’s great guy to work with. I have no affiliation with Rex or HyperVent… just helping to spread news on what I feel is a good, useful marine product.

Happy Condensation-Evaporation Daze! – Art
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Old 01-05-2015, 11:23 AM   #34
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I see it's mattress day.

Haven't had that problem for years ... since we got some hypervent.
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Old 01-05-2015, 11:50 AM   #35
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As just posted in the other mattress thread: we use wooden "Lattenrost " / slatted frame (?) under our mattresses and like at home they are dry ...


best regards / med venlig hilsen
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Old 01-05-2015, 01:22 PM   #36
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In the morning, we lift the mattress. Let it dry all day. We also have IKEA slats under it too.
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