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Old 31-12-2014, 03:30   #1
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condensation, condensation, aghhhhh!!!!!

Hello all, a well 'talked to death' topic, however there may be new solutions?? I have a dufour 30 classic and sail her near Belfast in northern Ireland and the surrounding waters Scotland, isle of Mann etc. Anyway, sleeping on the boat this weekend, wife daughter and 2 dogs, in the morning under the mattress was like a swimming pool and the sides were wet therefore edges of bedding in contact t were wet. I have read about using dehumidifiers, dry mat, rubberised coir, slats under the mattress etc I know I need to get air under the mattress but what do I do with the sides? I do not want to cover over the lovely gel coat/wood panelled cabin sides with carpet, however I need to do something to protect the bedding. For heat I have a fan heater ( does not run at night), my wife is against an eberspacher as I had one in the last boat and she does not like the dry heat!! So sleeping with a window open at night is hard due to the cold and if it rains the water will come straight in as the windows in the aft cabin open inwards. There is no forecabin, the boat is open planned and under the front berth is the water tank. Hopefully someone reading this has the same boat and has a solution?? All ideas welcome.

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Old 31-12-2014, 15:43   #2
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Re: condensation, condensation, aghhhhh!!!!!

Cold, wet boat, wife doesn't like dry heat?

SOMETHING'S gotta give.

New wife, new lower latitude?

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but not greed to want to take somebody else's money"

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Old 31-12-2014, 16:07   #3
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Re: condensation, condensation, aghhhhh!!!!!

Styrofoam insulation is the ultimate solution. Even then, we still use a humidifier but it's really easy to get it down to about 50% humidity and that's living aboard full-time.
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Old 31-12-2014, 16:16   #4

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Re: condensation, condensation, aghhhhh!!!!!

Yup, needs a new wife.

If you've got some attachment to the old one? Give her the credit card and tell her she's got one week to either fix the heat or pack her bags, let her figure out how to make un-dry heat while stopping the rain forest.
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Old 31-12-2014, 16:18   #5
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Re: condensation, condensation, aghhhhh!!!!!

I'd vote for the new wife.........
"Waste your money and you’re only out of money, but waste your time and you’ve lost a part of your life.” (Michael Leboeuf)
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Old 31-12-2014, 16:25   #6
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Re: condensation, condensation, aghhhhh!!!!!

Insulation, ventilation, dry heat...those are the solutions. Unless you love black mold.
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Old 31-12-2014, 23:59   #7
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Re: condensation, condensation, aghhhhh!!!!!


A whole lot of the condensation is due to your breaths, and the dogs. There's mega moisture in it

What the owner of our boat did was to insulate between the hull and the ceilings with spray in foam, and also under the deckhead. This means that the hatches weep condensation. If I lived where you do, I woud then add 1/4" closed cell foam to the underside of the hatches, cut to stay put by their tightness. It you have to have light, then make one or two 2 cm holes to allow light, but you really want the insulation.

When the bedding gets soaked, the best thing is to take it ashore and wash and dry it, but you need both insulation and ventilation, and something for under the bunks. We use 1/4" closed cell foam and do not get moisture under the bunk, but we are only at 42 deg. south, and it may be colder where you sail, maybe you'd want to go 1/2" thick.

Hope this helps, and happy new year.

Ann & Jim, U.S. s/v Insatiable II, SE Qld, for a while
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Old 01-01-2015, 09:55   #8
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Re: condensation, condensation, aghhhhh!!!!!

Eva Dry EDV-4000 dehumidifier. Liked it so much, bought another one.

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Old 01-01-2015, 23:20   #9
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Re: condensation, condensation, aghhhhh!!!!!

The horribly expensive mesh stuff under your berth mattress really works. Oil filled radiators work well when on shore power. A de humidifier, draining via the sink or bilge keeps mould at bay.
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Old 02-01-2015, 01:03   #10
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Re: condensation, condensation, aghhhhh!!!!!

Camping mats Wanderer EVA Hiking Mat - Single - BCF
7 or 8mm closed cell foam.
Doesn't need to be permanent... just tape in place against the hull.
Dampness under bunk? I've never had a problem with that but have a custom made s/s sprung mattress in the captain's stateroom and 4 or maybe 5 inch closed cell foam settees bases in the saloon for the crew.

Hatches and ports? I use cling film stuff to provide basic double glazing.

Oh... and try living closer to ambient... Icebreaker thermals and possum wool gloves....

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Old 02-01-2015, 03:31   #11
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Re: condensation, condensation, aghhhhh!!!!!

The matting under the mattress works well, cut ours so that it rises about one foot up the bulkhead and cabin sides. No condensation issues around or under the mattress since then.
And, as Ann and El Pinguino suggest, insulate the underside of the hatches. I just use bubble wrap which is held in place with the hatch blinds.
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Old 02-01-2015, 09:48   #12
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Re: condensation, condensation, aghhhhh!!!!!

This may or may not fix the condensation problem, but it'll definitely help the mattress & bedding.

Option 1:
- Get a carbide hole saw, & drill a grid pattern through the bunk tops, although not so many holes that you hurt it's structural integrity. That, or plumb in some sort of air intake hose/system to route air through the space underneath of the bunk.
- Then at the bunk fronts, cut holes for & mount a couple of those small computer fans found in desktops. In theory it'll help move some of the moist, condensing air out from under the mattress. If the fans turn out getting the thumbs down, you can cover the holes with stainless or bronze louvered grill plates.

This actually worked well, sans fans, on the double bunk on my last boat which I lived on. Much like you, with little heat, in a damp climate, including having a full shower which was frequently used. The boat was a 31’ Searunner Trimaran, which have only a bit more room inside than a Catalina 25’

Option 2:
- Get some 1"x2" stringers & cut off the top 1/4" rounded over portion.
- Measure your bunk at the height of these stringers, & get enough 1/4" or 3/8" plywood (exterior grade) to fill/cover the entire bunk.
- Cut the plywood pieces to fit the bunk (if a double bunk, place the “seam” wherever appropriate).
- Drill a grid pattern of 1 ˝” (approx..) holes with a carbide hole saw.
- Glue the stringers longitudinally to the bottom of the plywood, with the flat (trimmed off) side up.
- Paint & or seal the wood via whatever method suits you.
Also, you may wish to fill in the gap now present on the sides of the cushions with some closed cell foam, or other non absorbent material.
I had this on my last boat as well, & liked it a lot.It was on the single bunks.

Ann T. Cate’s idea for foam to help with condensation from the hatches is a good one. Though I made a trim ring, & put a few layers of bubble pack in it, so that I’d still get the light below decks.
Or, get a piece of Plexiglas a bit bigger than the hatch, & some weather stripping. And mount it using some DIY twist latches (turn buttons) affixed to the overhead.

Bubble pack is also a decent, inexpensive material to put up against the side of the hull in the backs of cupboards & other places out of site which need insulation. Or behind/under wooden ceilings & such. Though for cupboards & the like, you could go all out & try Mylar backed fiberglass house insulation.Doubt it’d absorb much, if any water (just a guess).

Also in the interests of light, you can make a hatch board which fills the top half of the companionway, cut a substantial sized hole in it, & bolt a piece of Plexiglas over the hole inside & out.Thus giving you a double pane “window”.



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