Monday, January18, 2021
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Keep your boat Dry

Preventing mold growth on a boat

Controlling mold growth on your boat

I saw Dave reading the electrical meters yesterday and we got to talking. He told me that some boat owners are running space heaters 24/7 to control the mold in the cabin. A few years ago I ran a series of experiments to find a way to control the mold on Papoose, my 36 foot wood sloop. The mold was so bad it was literally eating the hats I hung up below. When I opened hatches, water would be dripping from the cover. The boat was wet. This is the shortened version of what I found. The longer version is on my website.

First thing was to get rid of the mold. I literally brought a hose below and hosed off everything, and I mean everything. Then I donned a gas mask and sprayed a diluted bleach solution on all the hull surfaces, then washed that down. That got rid of the mold on the hull. Next was figuring out how to keep it gone.

Probably the worst thing you can do is seal the boat up and heat the air, which I tried as one of my experiments and what some people apparently are doing according to Dave. Hot air holds more moisture than cold air and mold loves hot air. There is a theory of sealed spaces that says basically they will suck moisture out of the outside air until the inside air is at 100% humidity unless they are hermetically sealed, which is impossible on a boat. I can't explain that theory but basically it leads to two solutions to keeping moisture out of the boat.

The most effective thing you can do it seal the boat up and run a dehumidifier. That will remove the moisture from the air and with a hose to the sink, get it out of the boat. That is not what I did. This is probably the only solution if you live in somewhere like Florida where it is hot and humid but that is not the case where here in California.

The next best thing you can do is keep the moisture in the boat air no higher than it is outside and keep moisture from condensing on the cold hull. You do this by ventilating the boat. Open hatches an inch, open cabinets, run solar fans, just basically allow air to flow inside the boat. In addition, you need to keep air circulating in the boat so that it will not condense. An effective way to do that is with a Caframo Stor-Dry. It has a 75 watt heater and a fan. It is not trying to heat your boat but rather to create convection currents that move the air around so you don't get condensation on the cold hull.

It was almost 8 years ago since I did my experiments and I am pleased with the results. My electric bill runs around $1 a month and the Stor-Dry is running all the time as is a battery charger.

Here is a link to a Stor-Dry on Amazon. It should cost $60-65.

Home dehumidifiers cost about $200 but I don't personally feel comfortable running a home product on a boat and marine grade ones are more than twice the price.

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