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Old 16-12-2008, 02:56   #1
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Stopping condensation from aluminum hatches?

We moved aboard our aluminum Dix 43 "Namo" last summer and now that winter has arrived in BC (-6 degrees centigrade, 21 farenheit outside now) we are not liking the amount of condensation dripping off our Lewmar aluminum hatches. The interior rain showers are becoming annoying, especially in the morning when the ice on the hatches melts. The boat has lots of heat from a 35K BTU hydronic diesel funace and is well insulated (Mascoat Delt-T plus fiberglass batts). Short of moving to Mexico, has anybody found an easy way of dealing with this problem? Perhaps we should paint the hatch frames with Mascoat Delta-T as well (although they wouldn't be as pretty)?

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Old 16-12-2008, 03:28   #2
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Blow air across the hatches.
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Old 16-12-2008, 03:41   #3
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Gord May
So whats the idea...the condensation still happens, but is disipated into the air before accumulating enough to drip?
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Old 16-12-2008, 05:02   #4
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Condensation occurs on inside surfaces (hatches) whenever surface temperature falls below the dew-point temperature of the room.

Blowing air across the hatch (window) helps warm the window surface temperature above the cabinís dew point, preventing condensation; and (as you suggest) helps to evaporate the already condensed liquid water, putting it back into the gaseous vapour state.

Warmer air is able to carry much more moisture than colder air, so as the temperature of air increases it is able to hold a greater volume of water. Condensation occurs on inside surfaces (hatches) whenever surface temperature falls below the dew-point temperature of the room.
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Old 16-12-2008, 06:14   #5
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Moisture laden air will increase when you breath in a confine space. This is in addition to the moisture in the air we call humidity. Duh. Cold surfaces will cause the moisture in the air to condense on them which is why we see dew on grass and condensation of metal (an other) higher U factor surfaces on a boat.

If you can keep everything warm enough the relative humidity inside the cabin will rise and it will feel steamy! ICK Conditioned air systems maintain the proper (comfortable) level of moisture in the air and will usually condense the water out of the air and return to a plumbing drain as "condensate".

Boats don't have such systems so the best approach is ventilation and then you are removing moisture laden warm air and tossing it out. This means your heating "costs" rise to warm up the drier cool outside ventilation air.

The driest heating system on a boat will be forced hot air with sufficient fresh air introduced. If you have dry air in the cabin you will have less condensate on cold surfaces. Duh. Ventilation and moving air is the key.

Many have noted that they have condensation in lockers. Duh. No air movement and moisture condensing from cold hull encountering the warm moist air of the cabin.

Install small fans in your lockers and get the air moving is the only solution plus lower humidity air in the cabin.

How about adding a de humidifier? It collects the moisture in the air and then you toss it down the drain.
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Old 16-12-2008, 06:25   #6
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I am a full time live aboard in the New York area. I solved the hatch frame condensation problem by building wood frame storm "window" that fits over the Lewmar hatch. A transparent acrylic top allows almost as much light in as the Lewmar hatch itself. I have six of these hatch covers on my boat, and along with plenty of small fans circulating the air in the boat, have virtually no problem with condensation. I have lived aboard this boat since 1999, and have (the hard way) learned the secrets of living comfortably through the winter. Hopefully this will be the last winter I will spend here
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Old 16-12-2008, 06:34   #7
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A little more on the storm hatches........it works by creating a "dead air" space between the inside air temperature and the outside air temperature. not really dead air, but an area of "buffering" temperature that keeps the alumminum from transmitting the cold into the inside frame.
I also use a similar idea on the large saloon windows of my boat (38 ft Irwin ceter cockpit sloop) I cut acrylic to the shape of the teak trim around the windows, attached suction cups to the acrylic, and stuck them to the windows (use a little bit of vegatable oil on the edge of the cups) They stay in place all winter!!! No condensation on the glass!!!!!!!!!!
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Old 16-12-2008, 06:43   #8
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Air movement is one of the most useful things one can do... we have also from time to time taped bubble wrap to clear hatches so we keep the light , and insulate the hatch itself.
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Old 16-12-2008, 07:46   #9
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Several years back we bought a portable de-humidifier from Amazon.com. It is not one of those little expensive SS units sold in marine stores, it is a Soleusair and it is quiet, puts out some heat in the process, and really helps dry out the inside of the boat. We can move it around in the boat to problem areas as needed. It removes the moisture and keeps air circulating in the boat. Solved most of our condisation problems. We also cut holes throughout the boat on hidden spots in the bulkheads and added vents to cabinets, under seats and most enclosed spaces.
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Old 16-12-2008, 09:44   #10
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I'd like to second the bubble wrap idea, this is our third winter in the UK, and I wish I had discovered it sooner. Just tape down one or two layers of bubble wrap over the outside of the hatch, and no more getting rained on inside the boat!!!! We also have a 240 volt dehumidifier, we don't do the ventilation thing as we would never be warm inside the boat.
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Old 16-12-2008, 09:55   #11
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if you have interior screens on the overhead hatches (like I do) you can put insulation between the hatch and the screen and condensation will be stopped. also keep boat as warm as possible to cut down on the humidity. fans help too.
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Old 16-12-2008, 10:02   #12
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Quote:
Originally Posted by gonesail View Post
if you have interior screens on the overhead hatches (like I do) you can put insulation between the hatch and the screen and condensation will be stopped. also keep boat as warm as possible to cut down on the humidity. fans help too.
Keeping the boat as warm as possible does not cut down on humidity and actually will increase condensation. It is the humidity in the air, and temp has nothing to do with except the temperature difference between the inside and outside of the boat that causes condensation. The greater the difference the more condensation. The only way to remove moisture in the air which is what humidity is, is with with a device designed to do this. Otherwise you can't remove it, but humidity alone does not cause condensation. That is why when it is 90 degrees in Floriduh with 90% humidity and your boat is open you don't have condensation. They are 2 different things although one is related to the other.
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Old 16-12-2008, 11:00   #13
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Well thanks for all the ideas on this (common) live-aboard problem. I think the hatch condensation is accentuated in our case by the fact that this is an aluminum boat and the hatch frames are in contact with the cold aluminum deck that chills the frames. This creates a big heat sink. Perhaps insulating the hatch frames from the deck with a layer of plastic (the same stuff used to insulate winch bases) would be a good long term solution? The bubble wrap idea seems easy to try so will give that a go first. The hatch boxes also sound like a good medium term solution. We already have a small dehumdifier and a powerful (Hurricane) diesel furnance with six hot water radiators so the boat is quite warm.
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