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Schooner Captain
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Discussion Starter · #1 ·
The thin areas of cockpit fiberglass condensate when its cold outside, and warm inside. These are not visible areas, but areas I have access to.
What product may I use to stop the sweating? The same thin area up forward has a padded headliner material, but it is discolored. Is this just adsorbing the water, or is being adhered preventing the water from forming?
Can I glue on the reflective bubblewrap for the same effect?
If so what adhesive would I use?
 

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Use a fan to move the air around more and try to get your inside temp up somewhat to stop the sweating! You can glue carpet Etc. to the over head, but it will probably only stay dry for a short time. You have to stop the sweating!!!!!
 

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You can do some good by warming the boat up to increase the water holding capacity of the air but if you really want a no-power solution, you'll have to insulate the hull so the surface temperature on the inside never drops below the dew point.
 

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Discussion Starter · #6 ·
You can do some good by warming the boat up to increase the water holding capacity of the air but if you really want a no-power solution, you'll have to insulate the hull so the surface temperature on the inside never drops below the dew point.
I will try 80 degrees tonight ;)
 

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I assume you have the concept down. Warm air can hold exponentially more moisture than cold air. When moist warm air hit a cold surface, the boundary air cools, the moisture can't be held and it condensates out.

As I said, the best method is to dehumidify the boat entirely, but that won't work well without power.

Insulation is a good way to keep the surfaces from dropping below the temperature that would cause that boundary condensation. The really tough part with insulation is truly sealing off everything to the hull. If you insulate the cabin, but air can still get behind the insulation, it will still condensate back there. You may not notice as you do now, but you have a breading ground for mold.

Here another angle. In the winter, the outside air is generally drier to begin with. The reason the cabin is too moist is because it's inhabitants are continuously adding moisture. Just exhaling does so, but you can limit other things, such as cooking, showers, keeping the bilge bone dry, etc. While seemingly counter intuitive, when the air outside is drier, you should be ventilating the cold air inside in the winter as well.

That brings us to the wood burning stove. It will actually help a great deal if you allow ventilation. As they exhaust extraordinary amounts of air, it has to be replaced in the cabin by outside drier air. It's a good thing.
 

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Discussion Starter · #8 ·
So for my test I ran both AC's full out last night, 81 degrees inside, not a bad sleep temp with a low dew point mind you. I did not get driped on all night, but the hatches and winds are still full of condensate, thou the middle of the windows and hatches are dry. Dehumidifer time, lol. I agree on the wood stove stealing lots of moist air, in exchange for cool low humidity air outside. Will be trying some insulation thou, as we are likely to get stuck on anchor some day in temps under 10 degrees.
 

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Last year when this subject came up I did some pondering on how to do passive dehumidification. I came up with two ideas.

But first, using clear bubble wrap on the windows will insulate and still let light in. And dead air space is the best insulator. So if you have a gap between your insulation and the hull, as long as the air space is air tight, it will increase the insulation abilities and will not condensate in this space.

Now for my ideas on passive dehumidification... if you have two copper coils or heat exchanger like a car heater coil, one inside the boat just below the cabin ceiling and the second exchange outside just above the cabin top, connect the two exchangers in a closed loop with a 50/50 anti freeze mix. You will need a condensation collecting pan under the inside exchanger and drain. Now the heat from the inside will heat the water/anti freeze and you will get a natural rise of the water and the cold outside water will naturally fall, creating a passive water flow cold in and hot out. A small fan on the inside exchanger would dramatically help the process, but not needed. You may need an expansion reservoir as well.

My second idea I have built, but not for boat use. It could be an issue with boat movement, this method would be better for a boat on dry dock. I did a bunch of research on these systems that use crystal in a container. They are very expensive and small. I found that many are just calcium chloride, ice melter. I can get a 50 lb bucket at BJs for $20 and bags at Home Depot for the same price. Take a 5 gal bucket, suspend a mesh bag over the bucket filled with the calcium chloride. The calcium chloride will melt when it absorbs moister and the condensation will drip in the bucket. I got a full 5 gal bucket from a 30 lb bag of calcium chloride. over a 6 month period. This was in a non occupied area, that process would be much faster with people in the room and higher humidly. This system is for 80% and over humidity. This calcium chloride water can also be used for ice melting.
 

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I forgot of a third method. If you take a light mill plastic, like a trash bag. And tape it air tight to a part of the ceiling with a small object on the top and middle of the plastic creating a upside down pyramid with the plastic. Condensation will collect on the underside of the plastic and do a controlled drip at the point of the pyramid, just put a bucket under it...
 

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When trying to come up with a solution for a similar problem in the same conditions & construction materials I came up with but never implemented the following: 1) spray-in closed cell foam insulation to a final depth of approx. .5 to 1.0 inches, 2) after any smoothing of the foam surface apply truck-bed liner to add a relatively durable surface to the foam, (possibly with a layer of cloth of some sort to help spread impact loads and increase abrasion resistance), 3) paint with the surface paint of choice with vacuum micro-sphere additive.
I have long since lost my notes regarding suppliers & specific materials but a search for "spray foam insulation kits" will get you a lot of resources in that line, same for truck-bed liner, just go looking for the fire rating & applicator options etc. that suit what you wish to do. BIG ARSED WARNING Home Insulation With the Stroke of a Brush will lead your to the REAL space program developed & proven vacuum micro-sphere supplier, avoid the liars, cheats and $#!*heads trying to steal from you with "insulating" paint/additive made with talcum powder or Cabosil and other bull$#!* fakes.
I never did the project that I came up with this for & don't know how durable the surface would be under the real-world year in and year out insults of contact with moving gear - supplies - crew hitting the overhead etc.
I hope someone with insulation - condensation needs finds this of use.
 

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I'm trying to imagine the nightmare of needing to access the gunwale, the deck or hull to address piping, cabling, deck fixtures, etc, after spraying insulation all over everything. It is, however, the only way I can see insulation working well.
 
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Cold camping in tents have what is known as a frost liner. This also works to absorb drips so they don't get to you! The liner is porous cloth suspended a couple inches below the surface the moisture is condensing on.
 

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Discussion Starter · #15 ·
I'm trying to imagine the nightmare of needing to access the gunwale, the deck or hull to address piping, cabling, deck fixtures, etc, after spraying insulation all over everything. It is, however, the only way I can see insulation working well.
there is only one portion of my deck that is not cored, and nothing resides inside it with the exception of electrical cables, and the bottom of the winch bolts. If I did the insulation by the wire, I would put a piece of aluminum between the wire and insulation...
 

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there is only one portion of my deck that is not cored, and nothing resides inside it with the exception of electrical cables, and the bottom of the winch bolts. If I did the insulation by the wire, I would put a piece of aluminum between the wire and insulation...
Yup. And, therefore, create a condensating pocket for moisture and mold.

It's a tough battle.
 

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These things are great... only if the temperature IN the boat stays warm. If the inside temp is down around 45 - 50F, the dehumidifier will run all day long and not suck any moisture out of the air. :eek:
Essentially true, although, the minimum operating temps for dehumidifiers can vary and some have a cycle to defrost themselves, freezing of the evaporator being why they stop working. Actually, in a confined space like a boat, the dehumifier itself is likely to provide heat.

Here's the balance. If it's truly too cold to functionally operate a dehumidifier, there isn't likely to be much humidity in the air. The air can't hold much water at cold temps, so there's much lower odds of condensation, and the occupant isn't likely aboard making any with combustion, cooking, showering and breathing. Once the "humidity making human" comes back aboard, the cabin is probably going to be heated back to an easily operating temp. If you live aboard, you may even leave some heat source on while away, although, that's dangerous. But at least to keep the cabin at 40-50 degrees so your pipes don't freeze.
 

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Essentially true, although, the minimum operating temps for dehumidifiers can vary and some have a cycle to defrost themselves, freezing of the evaporator being why they stop working. Actually, in a confined space like a boat, the dehumifier itself is likely to provide heat.

Here's the balance. If it's truly too cold to functionally operate a dehumidifier, there isn't likely to be much humidity in the air. The air can't hold much water at cold temps, so there's much lower odds of condensation, and the occupant isn't likely aboard making any with combustion, cooking, showering and breathing. Once the "humidity making human" comes back aboard, the cabin is probably going to be heated back to an easily operating temp. If you live aboard, you may even leave some heat source on while away, although, that's dangerous. But at least to keep the cabin at 40-50 degrees so your pipes don't freeze.
which leads to a good question that is somewhat related: if you want to leave a heat source running on your boat if you have to be away overnight, what type is safest?

most have safety features built in, now. i like the oil filled radiator types but you would have to make sure the base was secured so it didn't tip over. westmarine has that flat cabin heater...although the price is a little much for what it is.

however, are there any that are safe to leave overnight?

i don't have any flamable fluids aboard. so, for me, there is a reduced risk over someone with...say....propane.
 
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