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Old 23-10-2005, 20:54   #1
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Best option for keeping the bottom of the cushions dry

Ahoy Cruisers and other keepers of boating knowledge and wisdom.

I'm looking for opinions on keeping the undersides of the berth cushions dry. I'm tired of being out a few days, and checking under the berth to find all that "moisture" I'm giving off at night.

I assume I could lay down a layer of Dri-Dek tiles. I've seen that. But there are other options, and I just wanted to know if there are other products or techniques people have found better, more cost effective, etc?

Dan Leach
s/v Marie, Seattle, WA
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Old 23-10-2005, 22:31   #2
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The only option is to turn the cushion up after use. This is the most aggrevating issue we deal with on our boat. We have tried the DriTite tiles, we have tried the pads that are sold specificly for that purpose, and when I modified the master cabin on our current boat, I built a grate under the berth instead of a solid surface. We tried several different foams, latex, and even one of the plastic covered coil inner spring mattress'.
On our small boat, we have a cheap foam mattress. It came wrapped in plastic, and we have left it that way. but bought a cloth cover for it. We never spend more than 2 or 3 nights in a row on this boat, but it does seem to stay dry.
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Old 26-10-2005, 13:28   #3
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Thanks Kai Nui,

Good advice. It's kind of that I suspected. And if using deck tiles or other devices designed to get air circulation under the cushions don't really work...then tipping up the cushions is probably going to be my best course of action.

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Old 17-08-2008, 11:43   #4
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wet berth

I lived aboard in Seattle for 4 years. It's an issue for sure in the winter especially. Dri Deck tiles helped, although they have become unreasonably expensive. I believe there are other alternatives that are not in one sq ft snap together format. Previous comment was good though, make your plywood access lids into swiss cheese. This can be done with a drill press and hole saw in a manner that looks good with a little sanding of the holes and repaint. Then how about a small quiet computer fan to pull air through the lockers from below?
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Old 17-08-2008, 12:07   #5
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How are they getting wet? From condensation? If that is the case you have to keep the cabin temp above the dew point of the air. The only way I know is with a heater. It does not have to be a lot of heat either like you would get from a space heater. In the winter I use a low wattage metal rod called a "golden rod" that creates just enough heat to keep the cabin temp above the dew point.

GoldenRod Dehumidifiers
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Old 17-08-2008, 12:37   #6
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Thanks for this post, David.

I am off the grid (and will be this winter too). I have been looking for a way to keep my engine room(s) from freezing that wouldn't take up much power. This might be a good idea...
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Old 17-08-2008, 13:39   #7
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It might get better if you put som isolation under the plywood berths, like close cell foam mat. Anyone tried this?
/matti
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Old 17-08-2008, 16:33   #8
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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.

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 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, need to consider that if the fiddles on the side of the bunk are not high enough the mattress will not be restrained when the boat heels - not a problem on cats or for smooth water mono sailors though. If access to the storage space under the bunk is through hatches in the bunk top then this method can be inconvenient for access.

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.

4. Provide a barrier between the body and 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 "crinkly" when one moves.
Because we needed to keep our bunk heights down (due to the way it turns out from sole height, desired bunk width, and the shape in the side of the hull the fiddles on our bunks are too low to allow us to lift the mattress to ventilate underneath properly as in 2 above. Also, access to the storage space under the 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 - no humidity (don't know why) and no crinkling. Is just cut to shape, laid on 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.

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.

Sorry if that sounds a bit "school mam'ish" but is something I have had quite a serious look at so just passing on what I have found - hope it is of some use.
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Old 17-08-2008, 16:41   #9
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I don't have this problem. There is a material which is used to allow moisture to collect at the bottom of veneer masonry walls. It's a semi rigid very porous foam. I wonder if you could use this as pads UNDER your cushions. I think the material is 1" thick and it might provide enough air space for moisture to either evaporate or not wet the cushions.

It's an idea.
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Old 17-08-2008, 18:46   #10
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Midland said it -

4. Provide a barrier between the body and 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

Seal the mattress - keep water from passing through it to your settee/bunk base and you will not have a buildup. A mattress seal, with a 1" cotton foam cover over it, with a sheet over that will stay dry, won't feel "sticky" or be extra humid, and will keep your bunk dry.

These can all be bought at fabric stores. Sew the PVC cover to fit your cushion/mattress.

Best of luck!
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Old 18-08-2008, 15:49   #11
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If you can get to the underside of the deck supporting the berth cushions, add some insulation to isolate the decking from the spaces below which are chilled by the water in your area. You can buy self adhesive "Thermwell" duct insulation or "Reflectix", which can be applied with staples or double stick tape, from Home Depot very inexpensively. Once that's done, put a layer of "DryDeK" under the mattresses for air circulation, even if you use a vapor barrier under the bedding.

Cheers,

s/v HyLyte
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Old 18-08-2008, 15:53   #12
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How much is Gore-Tex? Would a mattress put in a custom made Gore-Tex bag work? Just throwing out the idea.
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Old 18-08-2008, 19:22   #13
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Dan Leach, We had this problem and got rid of it simply by making mattress covers out of heavy duty rubber backed curtain material.you can pick some really nice designs. Never had another problem and it was cheap too.Wife sowed up the covers, not hard to do. Boy it was bad before that, tried holes in the base etc etc nothing else worked. Natureboy.
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Old 19-08-2008, 08:54   #14
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My cushions are 47 years old and the covers have a plastic mesh at the bottom that seems to work real well. I'm in the PNW with a leaky (for now) boat and have had no issues with mold/mildew.
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Old 19-08-2008, 12:27   #15
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YACHT SPRINGS I believe is the name on Imagine. They are bowed slats with rubber inserts on the ends to hold them in place. Work well,and are comfortable on 2 of our full size beds. We removed them from our queen bed, because the slats did not cover from side to side, but to the middle. Fortunately the boat is so dry it has not become an issue.
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