Major mattress moisture help! (PNW)

[Katkiln]

Hi CF.

Currently a live aboard in PNW and have some major mattress moisture, any ideas?

Currently we sleep in the large rear berth of our Catalina 320 and have a Froli sleep system under 3” pads and still have quite a bit of daily moisture underneath froli system. We strip the bed and butterfly the mattress every day and when on shore power, run a small dehumidifier and the West Marine air dryer in the berth and the mattress is still clammy. I’ve taken all the bedding and pads out and dried them to Sahara level but the next day it’s still a bit damp. Our berth is mattress to wall almost 90% around the edge so not a lot of circulation at night when horizontal.

Considering adding a layer of Hypervent between pads and Froli..... any thoughts or anything I am missing? We spend 50% on-the-hook so anything high-power use will be an issue.

Thanks in advance.

BTW: The Froli is AWESOME- worth every penny for the comfort.

[Steve Bean]

Has the mattress ever been wet with salt water? This would make it hard to keep dry, as salt is hygroscopic.

[FastTrout]

Cut some lattice work and put it under, it will allow air to flow and should fix that.

It’s also cheap.

[Uncle Bob]

Seeing that you already have the froli system in place, Froli Travel, I would guess that the only other problem would be getting the air in there to ventilate. You say that the mattress is 90 percent to the wall, probably preventing air movement happening, is there any way to improve the ventilation to the underside of the mattress?
Of course, as has been previously mentioned, if salt water has been there previously then probably a new mattress is in order.

[noelex 77]

If salt water enters a (non closed cell foam) mattress or cushion it is very hard to eradicate the salt. Often at least a hint of dampness is permanent and replacement of the foam is the best answer, particularly if there is any resulting mould.

When threads on the forum discuss luxury cruising they frequently forget the basics. First, keep out all the water from the interior. Hatches, windows and deck fittings that do not leak even in rough conditions, when everything is flexing, are surprisingly rare on cruising yachts. It is also helpful to eliminate condensation and bilge water.

Before changing the mattress try to reduce the above problems as much as possible.

[Chotu]

What percentage relative humidity are you achieving in the air using the dehumidifier?

[gonesail]

even breathing in a small space releases a ton of humidity. without a dehumidifier you could run a small vented propane furnace at night? best to get the humidity down below 60% which may not be easy when at anchor

[JebLostInSpace]

I wonder if you could mount a small fan (like a computer fan) in the back wall somewhere to promote airflow directed in the gap provided by the Froli? They take so little power it would be negligible, and in such a small space it may have a positive impact.

[SV DINGO]

Hi Katkiln,

without sarcasim i am very happy to see your post as i had this problem and nearly went craszy over it and had endless arguments with my wife.

I am not saying that i found the solution but all i can tell you what my situation was.

I have a Van De Stadt Caribbean in steeland i am currently in Tasmania where the water is freezing and the temps are very low. I have plywood sheets on steelframes bot in the V berth and in the Master rear cabin. I have 4 inch foam in the Master and 5 inch foam in the V. The underside of the foam was dripping wet and stained the ply and stunck of vinegar.
My wife found big rolls of some medical absorbent paper in a local 2 dollar shop. The paper was used 4 fold on the ply. In the V we used a bedcover , thick and with some sort of padding in the middle on top of the paper, just folded to suit the V so overlapping in places. Result after 1 week when we checked it. No wetness , no vinegar small. In the master we used the paper , 2 Camping blankets, not so thick plus the lee sheet covers which we dont use on top of the blankets. Foam on top. Again no wetness or smell after a week. For us the problem seems to be fixed now but thius is just what we did before we jump overboard in total disgust and frustration. Good luck.

[chris mac]

We use the froli as well.i agree it is fantastic.
In terms of the moisture, what is under the bed? I assume storage. Ours has finger holes in the top boards which seems to allow any moisture to drip down to the bilge. Or gives a little more airflow. Either way, it keeps it dry.
Goodluck!

[Pete7]

Originally Posted by Katkiln

Hi CF.

any thoughts or anything I am missing? We spend 50% on-the-hook so anything high-power use will be an issue.

What are you using for heating and what do you have in the way of ventilation. I appreciate that you are in the PNW but you still need ventilation on board.

Do windows also drip in the morning?

Pete

[Katkiln]

Wow- thanks for all the great replies and ideas.

A few more details for those who ask:
- mattress has never seen salt and windows don’t leak.
- underneath the berth is where the engine shaft and water tank is (tank doesn’t leak) and is a mix of removable access boards and fiberglass.
- current humidity is 70%. A larger dehumidifier might help when we are on shore.... but not at anchor.
- I’m located in the Pacific Northwest of North America where water temps are 9 degrees and inside air is generally 21 with high humidity and lots of rain.

Since the mattress is boxed in (no way to pull it away from walls while sleeping) I think installing small computer fans is probably a good start as it’s looking like I need air-flow during the evening too.

Wondering if adding Hypervent would help as well or is the Froli and a computer fan enough?

[Flyrod1]

I have a fiberglass RV and use this dehumidifier to control moisture. It comes in different sizes.

Works remarkably well.

https://www.amazon.com/Pro-Breeze-El...s%2C164&sr=8-6

[bcboomer]

We are in the same climate and had the same issue. I found our solution on a blog and it has worked perfectly for 6 years.

We have an electric mattress pad underneath the mattress. Every morning we turn it on for 3 or 4 hours. Because the pad is on the bottom of the mattress the heat evapourates the moisture that builds up overnight.

We still have hyper vent and insulation below that but, until we put in the heated pad, we were plagued with th same problem.

It only uses 60 watts of power so we can even use it on the hook.

[pjhagbard]

The problem is NOT ventilation. The problem is lack of damp barrier!!

As close to the warm body as possible you should insert a damp barrier. Easiest to understand is a plastic shield. In wooden houses it is used in the walls/Cieling etc. and best is to place it just elow the sheets. But you won't lika that of course!

So if you can find a "bed protection" with breathing functionality what is used in hospitals and baby beds - and put that below the sheet, if you have a topping matress you can put it between a thin top matress but on top of the thick mattress.

Why this? Well, the warm air close to your warm body can absorb a lot of humidity. When this air (damp) transport itself down the mattress towars the cold surface (hull is colder than your body), the air gets slowly cooler the closer to the hull you get. And the same experience you can see when you take a cold beer can out of the fridge a warm sunny day - it gets wet on the outside - the same is the reason you get humidity below your matress. The bottom of the bed is the bear can!

IF you var a lot of holes in the bottom of the bed - the transportation will continue further down... and the water will be found on the inside of the hull. But as long as the bed is "solid" no expensive froli system will make any substansial different, exept in your wallet!!