Cabin Moisture Problems

[hamham]

The sailboat I purchased this past spring has mositure problems especially in the aft cabin. It seems that the coldness of the sea water causes condensation on the inside hull surfaces which in turn soaks the bunk cushions. The problem is too severe for the dry bunk product. While I plan to install solar powered vents and such, does anyone have any experience with using some sort of insulation material against the hull? I was thinking that closed cell foam might work?

[paulk]

We thought we had a leaky port causing wet bunk cushions until our steering cable parted (Just after rounding a bell in a race, reaching off at 9kts in 25kts of breeze). When I went below to see what was happening, (after passing up the emergency tiller), I noticed that a spout of water was shooting up the rudder post and finding its way to the leeward bunk each time we came down off a wave. At anchor the waterline is below the rudder bearing, so we wouldn''t have known about the problem if we hadn''t been under sail. My point is that there may be more than condensation causing your problem if your cushions are really getting wet.
Many metal boats DO have condensation problems, but these are not limited to just one section of the hull. For them, the solution is to apply foam insulation, as you suggest. I believe Ferenc Mate has a section on it in one of his boatbuilding books. Generally fiberglass boats have less of a problem with condensation, especially if they''re cored hulls, but if condensation is the problem, ventilation and insulation should help.

[WesleyBailey]

There are some electric heaters made especially for drying out boats, but I use an ordinary electric heater on a timer to help keep my Pearson 30 dry in the wintertime. Of course, that only works when there is shore power available. I also run a small fan to keep the air circulating when the boat is closed up. It still gets wet when we spend a lot of time on the water, but I think that it is because of moisture in our breath as much as anything.

[DonovanRig]

Closed cell foam will help. The main problem is that the moisture in the air condnses on the colder hull surface. The solution is to lower the air''s moisture content, its relative humidity. Relative humidity is the amount of moisture air can carry. 100% is the maximum, above that it rains. When the temperature rises, the air can carry more mositure, so even if the moisture content remains the same the relative humidity goes down. You lower the relative humidity by heating the air. However, if you just heat the air, and do not change it, eventually it will absorb more moisture and its relative humidity will rise. The solution is to bring in cold outside air, and heat it. Then the relative humidity will drop. Then circulate the air, so it picks up any moisture condensed on cold hull walls or elsewhere. Then exhaust the air. This can be done by having a heater in the cabin, a fan for air circulation, and a way to force in outside air and/or force warn cabin air out.

[Lusk]

We are living aboard our boat and really had a condensation problem until we insulated the boat. We used a material that looks like bubble wrap on one side and somthing like aluminum foil on the other side. I forget the name of the product, but it is sold at Lowes or any home improvement type of store. The other suggestions about heat and ventilation are necessary as well