Under Mattress

jacksaid

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29 Jul 2002
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Can anyone recommend a solution for preventing condensation under a mattress ?. I have looked at the proprietary matting products at boat shows, but they seem incredibly expensive - about £68 for a single berth
 
Air the mattresses after use, and stack them between use (eg when you leave the boat, stand them up behind the lee cloths).

The matting doesn't prevent condensation, only allows air to circulate as the moisture drains through.

There is no substitute for a good airing now and again!
 
As Andy says, it's a question of letting aire get there. One solution could be to drill 6 mm holes in the (probably) plywood of the berth bottom. The solution adopted by the original upholsterers of my boat was to have the bottom of the mattress cover made of "Naugahyde" (can't remembrer whether that's the English or Amereican name of the stuff - it's a leather-like PVC matetial). I haven't as yet noticed any condensation, even when going to Nova Scotia and Newfoundland.
john
 
Condensation occurs when moist(perspiration-laden) air reaches a cold surface - on bunks, normally a plywood base.
I have found that Andy's & John's solutions work well enough but an effective(and cost-free) solution is to proceed as follows;
Before replacing the mattress covers after their next wash, insert a thin polythene layer across the top of each mattress - a single layer of black bin-liner works fine. The polythene can be temporarily held in place with sticky tape. Care needs to be taken to avoid holes or gaps/overlaps.
The polythene layer stops the moisture reaching any cold surface and condensation is avoided. I have found this method works well, even with heavy usage and I have had no complaints about the presence of the polythene - most seem unaware of it.
Hope this helps.
 
Sorry for the delay - only just joined! You mention products already on the market, albeit expensive. Can you remember the manufacturers' names? I've tried several methods, but so far have drawn a blank. I'm getting to the stage where I'm willing to try anything within reason!
 
I used slatted berth bases made from 3x1 inch pine, with a one inch gap between, topped with coir (coconut fibre I think) matting then the mattress on top. I have also had success at preventing condensation by putting a thin layer of closed cell foam between the mattress and the matting.



Despite the high cost of living, it still remains popular.
 
Try this first...

Invest in a hole saw for your electric drill, and drill a load of 1" diameter holes in a 6" square grid pattern all over the bunk board. This will help to provide the ventilation you need to minimise condensation. And it's a lot cheaper than fancy bits of padding.
 
We installed propietory matting under our bunk before setting off for the Med 5 years ago and have never regretted it. I can't remember the name but it is rather like a 30mm thick, plastic scouring pad or one of those scotchbrite pads.

Before we forked out for the matting we considered the idea of drilling ventilation holes, but the entire under-bunk space is taken up with water tanks (fresh, grey and black!) They are cold, of course, so allowing the air to come in contact with them would make the situation worse, not better.

Increasing the flow of air does help to prevent condensation. With no flow the air rapidly increases in humidity to 100% (dew point) and then condenses. Circulation replaces this very moist air with some less moist air from elsewhere. If the night is very cold and very damp, nothing will prevent condensation, but a good circulation of air does reduce localised condensation beneath your bunk.

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