Damp mattresses.

[Wardy]

Like on a caravan, most of the boats i have been aboard have a foam mattress/seating placed on top of solid plywood (or similar) bases. In my limited experience of living in a caravan (soon to be a boat) this causes a lot of damp as any moisture tends to NOT escape as the system does not breath sufficiently.
Would it be a viable option when re-designing seating and berth areas to use slats of wood underneath the mattress, supporting the mattress and with an air gap underneath the slats leading out into the cabin (say about an inch deep) allowing a free flow of air underneaththe mattress? Or...
Is it the mattress (foam) that causes the damp build up and would it be better to just change to a different material make-up? If so, what is available?

I hope I have explained this query sufficiently

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[Dave99]

You can buy a material which is designed to combat this problem - its like a thick matting which is meant to improve air flow. I don't know if it works or not - quite a lot of chandlery's sell the stuff. Compass have a similar underlay and also a slat system which involves a roll of battens which lay on top of the plywood.

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[tillergirl]

Well slats is what some of wooden boaters have only experienced. And the foam is pretty dry - certainly the air circulates which is good. But then I regret to admit to a bead of moisture in the bilge so the circulating air has a dampish tinge to it.

Slats are not as convenient to make as ply bases and will need to be more robust.

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[VicS]

There is a material called Vent Air (I think) for use under foam seating cushions/mattresses to overcome this problem. It's available from upholstery suppliers and some chandlers and it may available from caravanning outlets, perhaps at lower cost.

<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>

 

[MainlySteam]

This problem is a regular one and the answer is easy - although many are confused by the different solutions required for managing general dampness in the boat rather than the problem you have set out.

Moisture migrates from warm to cold areas (same happens in houses, cold stores, etc) so if there is a vapour barrier between the warm part and the cold part then the moisture will collect on the warm side of the barrier. This is not condensation as many assume, it is just water that cannot go through the barrier to get to the cold part. So when you live aboard and are in the bunk the moisture from your body is driven from the warm bunk down through the mattress towards the cold underneath. If the mattress is not closed cell, or there is no other barrier, then when the moisture reaches the solid bunk base it cannot readily go any further to get to the cold area underneath and so collects and makes the bottom of the mattress wet.

There are 2 solutions. One is to keep the underbunk area well ventilated with cabin air and having the mattress on an open slatted base so the water is not prevented from being exposed to that ventilation. This is the type of fix you are suggesting. If doing it one has to keep in mind is that what one is doing is driving the moisture into the space under your bunk and if that space is also used for storage, especially if clothing or the like, you may create a new problem in that space, especially as the moisture may then condense on cold items and panelling in it. I have seen this method used successfully in a cruising boat built for cruising to cold climates, but in that case the under bunk area was completely open underneath to the cabin and I suspect that is what is required if the method is to work well.

The other solution is to create a barrier so that the moisture cannot get from the inhabited part of the bunk into the mattress at all. It can be done 2 ways. One is to use a closed cell mattress or overlay on top of the mattress so the moisture cannot get into it - however closed cell foams can be expensive and firm. The second is to put an impervious sheet on top of the mattress and that is what we do with 100% success. We use the sheets of thin soft plastic material (it is not the PVC type so is not crinkly and has no odour) that can be got for lining babies beds or those of others with wetting problems. While this solution works one has to be aware that the moisture then cannot go down so ones bunk tends to feel more humid than usual but is helped if good over covers are used that allow the moisture to readily migrate up and into the cabin air.

If ones boat is big enough, specially built thick innersprung mattresses also work but for most of us those are impractical and also make it difficult if there is top access into storage under the bunk. There are also various grids, etc that can be bought to create air space between the mattress and the solid bunk base but these are both inconvenient if one has top access into storage under the bunk and from what I have been told by those using them they still do not oftem provide a 100% answer (the moisture travelling down through the mattress may still condense on the cold bunk base) - I suspect they are more useful on narrow bunks and with ventilation to the bottom of the mattress from both sides.

John

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[rhc21]

We have used Ventair and found it works very well. Not that cheap but then what is nowadays?

Richard

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[FWB]

We use Ventair and it doesnt work. I suspect that this is because there is a lip on the base of the bunk to stop the mattress sliding off. The closed cell foam seems to be the answer then. When we ordered the mattresses we chose not to have this as it was Very expensive-----I wish we had now.

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[Guest]

Having had caravans as well ...

and boats for years .... your post is true and hits the problem quite square. Most people rely on good ventilation and lifting the mattresses when not in use ....

Biggest enemy of boats is lack of venting the cabins in the moist atmospheric area they live in .... common is to put hand down side of mattress next to hull and find it damp .....

My solution is to lift mattresses when not in use and allow the bases to air .... The main cabin entrance (washboards) have a permanent slatted vent in top board ..... near forward cabin has a mushroom vent that is kept open ...... the air flowing through effectively keeps damp down. .....

One factor that affects it as well .... a lot of earlier boats have no internal moulding to keep hull sides separate from internal furnishings ..... the hull side is against cold water etc. My boat gets around this by carpeting being applied to the hull sides internally ..... effectively a barrier to the cold and damp.

It all boils down to common sense and practical attitude .... my boats stays in most winters - is left for long periods and still is reasonably dry and mould free ....... without De-humidifiers and fancy gimmicks.


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[Guest]

All material solutions ....

move the problem from one area to another ..... so as I see it and have experienced with my boat ... the only true solution is to cure the production of the moisture wherever possible.
It cannot be 100% successful thjough and combinations of ventilation and mattress procedures evolve into a reasonable answer.

<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[andyball]

tried ventair on ours, with large lip & had good results....huge latex mattress much worse than old cheap foam one.

With old mattress, could use foil/air bubble insulation under ventair & no damp in the morning... comfy latex one is damp unless insulation removed exposing small vent holes in base.

Compass catalogue sell similar stuff, but w/o facing fabric from the picture, same sort of price though.



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[Guest]

Forgot .....

A very important factor in all damp / mould matters on boats ..... I have found that it is very important to never allow anything especially plastic wrapped such as sleeping bags etc. to touch or press on deckheads, hull sides etc. ...... It is common to see sleeping bags rolled up and stuffed into forward vee cabin berths .... touching the deckhead .... pull it out later and you have a damp top of bag .... in bad cases you can a small pool of water collected that spills when you move the bag ! Seen it, got the T-shirt ......


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[LittleShip]

Warm air holds more water than cold air and when the warm air passes over a cold surface the moisture condenses on it and causes dampness or mould growth. There are 2 ways to reduce condensation:-
1. By heating and ventilation
2. Move the boat into a much warmer climate.

I like the idea of number 2 personally /forums/images/icons/smile.gif


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I wish I'd been born rich instead of good looking ?

 

[dralex]

I don't know how you can sleep with an impermeable sheet- the onl;y time I've ever done that is at work in on call rooms and it's horrible- ie really horrible. It gets all cold, clammy and damp. The only good thing it's for is protecting your mattress from "things". You may as well sleep in a dry suit IMO.

I much prefer the ventilation way of doing things ie mattress cushion turned over each morning.

<hr width=100% size=1>Life's too short- do it now./forums/images/icons/wink.gif

 

[MainlySteam]

We cover it with a blanket (mainly to protect it as it is quite soft and thin) and use breathable bedding over us, and no particular problem at all. Certainly not with cold - in fact quite the opposite in that department. I suspect that the stuff that we use might be much thinner than what may be used in hospitals and it is also very soft and flexible, almost like a very thin fabric, so hasn't got that cold feel to it that plastics have. Don't know what it is called but it came from a baby gear shop.

We found when living aboard that, as others I know have, after months of using the airing the mattress approach the moisture and mould gradually gets the advantage, especially in the winter when things do not dry as well.

John



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[Abigail]

When we moved aboard, due to bad backs we invested in a really good mattress and it was worth it. The original 'underlayer' was the coir matting and it was not good at all - got very wet itself and sat there! So we changed it to ventair and really like it. We find it works very well.

We then found some moisture in the storage lockers under the bunk, particularly the one which also contains the steering quadrant. We insulated underneath the hatch cover with closed cell foam (which we bought in huge quantities anyway to insulate the hull, but is indeed expensive if you buy it in 6' lengths from a foam shop!) and that has reall helped solve the problem.

But ventilation really is also key - good dorade or other vents, and, if you're not living on board, maybe a small 12v solar fan to keep the circulation going. This is at least as important as all the stuff under the mattress.

HTH

Sarah

<hr width=100% size=1>Sarah & Pip

www.greatlittleboats.com
UK & Ireland distributors of Swifgig

 

[Rum_Pirate]

Try this product. It is not too expensive and is avaliable in 1/8" and 2" thickness 24" x 120". The 2" thickness is US$19.99 and can be cut into any shape.

http://www.westmarine.com/webapp/wc...10001&classNum=468&subdeptNum=467&storeNum=15

Trust that this is of help.

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[dralex]

I think that's the difference- I don't live aboard- YET.

It's all part of the plan though.

Alex

<hr width=100% size=1>Life's too short- do it now./forums/images/icons/wink.gif

 

[Benbow]

In case you find it useful

If you go to www.tinyurl.com
and paste in a long url like that one (178 characters), it will construct a tiny url so that now

http://tinyurl.com/45843

points to the same place and is much easier for others to cut and paste (and doesn't wreck the layout of the table!).

Cool ?

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[BrendanS]

It's a handy site, and I've used it for ages, but you can do the same thing on the forum quite easily anyway, like this <A target="_blank" HREF=http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&langId=-1&catalogId=10001&productId=37863&catalogId=10001&classNum=468&subdeptNum=467&storeNum=15>click here</A>

just type [ url=insert your link here]click here[ /url]

but with no spaces

<hr width=100% size=1>Me transmitte sursum, caledoni

 

[MainlySteam]

Yes, when living aboard things are never as comfortable as one might really like - quite a few compromises in fact. However, was recently talking to an owner thinking about a new yacht for himself and is angling towards it having, if possible, as much room and comfort as his apartment (including floor area and headroom) - thinking maybe 60 m LOA, but oh the compromises still /forums/images/icons/frown.gif.

John

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