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Old 01-01-2009, 12:16   #1
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Cushion Mildew

Have any of you gotten mildew on cushions that were not getting wet from things like leaks?

In other words, have any of you gotten mildew on cushions from simply sleeping and sweating on them?

I have gotten mildew on the underside of the 2 sleeping cushions on my boat. Before I replace the foam and wash the covers, I want to figure out if I am doing something wrong as far as ventilation goes. My boat is fairly dry (2 VERY small hatch leaks that will be fixed in the spring) and neither of these cushions have been leaked upon.

My confusion results from the following: It is somewhat likely that one of the cushions had the mildew when I got the boat. It is highly likely that the other cushion, which was located in an underway bunk with a 1ft high wall on the open side had some liquid spilled on it during a party and that the liquid that slid under the cushion was not properly dried, thus leaving a wet undersurface.

As a whole, I am working on better ventilation in my boat and other means of keeping it dry and mildew free. I am wondering, however, if people have found the need to put any sort of raised lattice under cushions, particularly in small, fairly enclosed berths.

Thanks so much,

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Old 01-01-2009, 12:28   #2
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Hi Sasha:

I have a problem with a 6" thick cusshion when I sleep on it moisture gets all the way to the bottom of the cushion. I plan on adding some method of raising the cushion that will allow air to circulate under the cushions. Don't know if that will fix it or not.

Fair Winds,


Between us there was, as I have already said somewhere, the bond of the sea. Besides holding our hearts together through long periods of separation, it had the effect of making us tolerant of each other's yarns -- and even convictions. Heart of Darkness
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Old 01-01-2009, 13:42   #3
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We have heard some really good reports on this system

Froli Sleep Systems by Nickle Atlantic, LLC
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Old 01-01-2009, 14:58   #4
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If the wetness is occurring from sleeping in the bunk it is due to the moisture sweated from the body. The problem comes up again and again in forums and the following is what I have posted before.

Moisture travels from warm regions of a structure to cooler ones (anyone who has been involved with the design of big freezers and cool stores in the meat and food processing industries or with the design of vapour barriers in other buildings will be familiar with that). So the moisture sweated from the body is driven from the warm part of the bed towards the cold bunk top which forms a barrier to it progressing further and so it "puddles" (I am avoiding the misleading use of "condensation").

There are 4 solutions that I know of -

1. Ventilate the bunk top into the space below. This generally, in my observation, requires the likes of replacing the bunk top with slats, just drilling big and lots of holes is not enough. I, personally do not like this for modern boats as the space under bunks is normally not well ventilated so by doing this one is just transferring the dampness problem into the storage space below. I have seen examples where this has been done though in custom built boats using slats for the bunk top and ventilating the space under the bunk up between the side lining and the hull to ventilate out of slats into the cabin space - the ventilation gets driven by convection and works well.

2. Raise the mattress on a grid or whatever so that there is good airflow under it so the moisture driven down through the mattress is carried away. From what I have seen quite a lot of free air space is needed to provide adequate ventilation. Also, one needs to consider that if the existing fiddles on the side of the bunk are not high enough they will need to be raised else the mattress will not be restrained when the boat heels - not a problem on cats or for smooth water mono sailors though. Also, if access to the storage space under the bunk is through hatches in the bunk top then this method can be very inconvenient for access to the storage space.

3. Use a normal thick household type mattress which is made to go on a hard base. It should be thick enough and open enough in structure to self ventilate. It may not self ventilate sufficiently if one long side of the mattress is against the hull side lining ie if it is not on an island berth.

4. Provide a barrier between the body and the top of the mattress so that moisture cannot travel down through it - this is the method we use. This can be done by using the plastic/rubber materials used in hospitals/child beds/etc to prevent wetting from urine, blood, etc BUT all the materials of that type I have tried raise the humidity in the bed to what can be for some an uncomfortable level even if light bedding is used over. They are also very "crinkly" when one moves in the bunk.

We needed to keep our bunk heights down (due to the way the heights turn out from sole height, the desired bunk width, and the shape in the side of the hull) and the fiddles on our bunks also being too low to allow us to lift the mattress to ventilate underneath properly as in method 2 above. Also, access to the storage space under our bunks is through hatches in the bunk top.

After trying a number of materials we found that a very high quality, very soft and quite expensive "vinyl" (don't actually know what plastic it is) fabric used for upholstering furniture worked perfectly - little extra humidity in the bunk and no crinkling sounds. Is just cut to shape, laid on top of the mattress and a thin under-blanket placed between it and the bottom bed sheet. I was led to using this material by a race boat owner who had all the mattresses/settees upholstered using this type of material for ease of cleaning and he reported no dampness underneath. Another forumite here uses rubber backed curtain material successfully, a material I had not thought of using and seems an equally good solution to try and likely cheaper.

It should be noted that heating the cabin does not cure the problem. In fact it may make it worse if the space under the bunk is not also heated as otherwise the temperature gradient between the top of the mattress and the cooler bunk top will likely be increased providing more driving power of the moisture from the sleeper towards it. Ventilating the cabin is also of little use.

Dampness under the mattress can also be caused by moisture condensing on the side linings of the hull and running down, but this will be obvious and the problem as outlined above will still predominate.
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Old 01-01-2009, 14:59   #5
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cushion rot


What you describe is a very common complaint amongst live aboards. The cure is simply some means of ventillating the underside of the matress. There are proprietary pads available at many places -- usually some form of "hairy" low density structures -- and they usually work quite well. Unfortunately,many are quite dear in price, often equalling the foam in cost. We found some very cheap doormats made of woven fiber (seaweed?) from Viet Nam (about 2$ Australian each) at the local big hardware emporium. Six of these lashed together were enough to lift a full sized double mattress off the boards, and conpletely elimintated the mildew problem. A mild aroma of seaweed arose from them for a short while, but it didn't seem a serious difficulty!

For once, there is a good solution to your difficulty, mate, so enjoy!


Jim and Ann s/v Insatiable II lying Gladstone Qld Oz
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Old 01-01-2009, 15:20   #6
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Well, these are all great suggestions. Thanks so much for taking the time to post them. Since I do live aboard and I am sure that none of the moisture is coming from leaks it is good to know that this is a common problem that does in fact need a solution.

Jim, just to be clear, you DID have this problem, right? Because it sounds like your solution is the easiest and most direct for a quick, inexpensive solution. There is a hatch in the bunk top but I don't use it very often. And since I work as a diver, I rather like the smell of seaweed...

MidLandOne, thank you for the discussion of the moisture travel. I know about this in regards to refrigeration but I didn't expect the moisture to go so thoroughly through the mattress. I also like your racer friend's idea of actually upholstering the matress with waterproof material. It is something to think about if I ever redo any of the cushions.

Ultimately, the Froli system sounds nice and would make someone who loves me very happy but money is tight right now.
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Old 01-01-2009, 15:37   #7
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Every day or two I just flip mattress up when I get up in morning,by afternoon its totally dry.Cost ;0 dollars.
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Old 01-01-2009, 17:18   #8
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I'm with highseas on the simple solutions. Many years ago (I refuse to say how many) I lived in a fairly small town in Switzerland. In the cool months, most houses would have their duvets (down comforters) hanging over the balcony railings or out the windows. It's amazing how a little fresh air and sunlight can take care of this problem.

But, perhaps a very efficient fan and opening the hatches in good weather is a good solution.

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Old 02-01-2009, 10:26   #9
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Yep, we did indeed have the mildew problem,and the doormats did cure it. The suggestion of flipping the mattress would also work, but in our case thecushions in question were not symetrical (sloped outer edges to match the slope of the hull that they lay against), and so that was not an option. Flipping would also require re-making the bed from scratch each time which is not a popular activity for most folks.

Opening hatches, etc, will not address the situation, incidentaly: you need the circulation below the cushion, not above it, and you never know when rain will arrive unexpectedly!


Jim and Ann s/v Insatiable II lying Gladstone Qld, Oz
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Old 02-01-2009, 12:19   #10
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Heat flows to cold, where moisture condenses. Unless you can create an hermetic environment on a boat, the daily cycle of heating and cooling brings all the moisture to your berths, leaky hatches or not. The single best solution is to ventilate the bottom of the mattress. period. You can do that with pricy vented box spring matresses, custom plastic springy gadgets, synthetic or natural spongey stuff, or slats in place of plywood bunks. Natural materials are the least expensive solution. Coir, a natural mat produced from coconut husks comes in a variety of densities and thicknesses, and does the job admirably. Frequently coir is rubber coated, making it much more durable in a marine environment, but its tough to begin with. Its used as plant bedding material above a hydroponic fluid in hothouses, and lasts years.
It is natural, a profitable low tech crop in many third world economies, and can be recycled. It is used in many boat bedding systems in combination with other materials, such as latex foam. A web search on marine bedding mat condensation will turn up a half dozen hits in the first two pages, including Dry-mat, Naturalmat, vent-air, hypervent marine mat, airflowsprings, etc.

Coir is also used in household scrubbing pads, with or without additional abrasives, and has been used with heavier coatings as a sturdy packing media for fragile objects.

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