A few weeks ago we were debating whether or not a homemade swamp cooler would cool a mid sized boat during really hot weather. Lots of pros and cons, but after researching the cost of construction I decided to give it a try.
The cooler chest is a good quality Coleman that was purchased at BJ's Wholesale Club as a closeout for $12.95. It's a 36-quart cooler chest that came with a small 6-pack chest at no additional charge.
The fan, a 12-volt, 120-mm computer fan with 4 blue LEDs was purchased online for $6.99 with free shipping.
Another $4.99 went out at Radio Shack for a universal, 12-volt cigarette lighter plug.
I had some scrap paneling in the shed and lots of scrap speaker wire in the workshop, which rounded out the parts needed for construction.
About 18-pounds of ice was placed inside the cooler chest. A 7-pound block, a 6-pound bag of cubes, and another partly filled bag of cubes that probably had about 5-pounds in it.
The boat's cabin was about 84-degrees when all the hatches were shut and the swamp cooler fired up. The fan is dead quiet, and within a few seconds the air emitting from the vent holes was ice-cold. The blue LEDs served served as a great nite-light and provided a soft, blue glow in the main portion of the cabin. This turns out to be a great asset for old codgers with BPH that have to get out of the sack and visit the head a couple times a night.
It took about 2 hours before the cabin temperature was a comfortable 72 degrees. While I waited I watched the second half of a pre-season football game on the flat-screen TV. As anticipated, the humidity remained quite high inside the cabin, but at least it was cool enough to sleep comfortably. I have no way of measuring the humidity, so I don't know if it increased, but at that point I really didn't care.
At 4 hours the temperature had fallen below 70 degrees, which was just fine with me. I had to use a light blanket to keep warm. (Old folks get cold when the temperature falls below their age!
That's why we go south in winter.)
The ice lasted about 5 or 6 hours, but the air coming out of the swamp cooler was still relatively cool because the water in the cooler was ice-water. It took about another 2 hours after the ice melted for the water to warm to the cabin temperature. By that time I was cooking a cheese omelet with some chopped, sauteed onions and mushrooms to go with my English muffin and a couple strips of bacon. The stove, obviously, caused the temperature to rise a couple degrees, but it was still comfortable in the cabin.
The swamp cooler is by no means an economical method of air conditioning the cabin. It can, however, make life a lot bearable on those evenings when there's not a breath of air blowing where you're anchored up for the night and the temperature and humidity are in the mid 80s. I DO NOT believe it would be beneficial to use it during the day - it just couldn't handle the sun beating down on the cabin and hull. There are other benefits, though.
The swamp cooler can still be used as a cooler chest for keeping the booze and food cold. Additionally, the computer fan insert can be used as just a fan. It can be propped up on the opposite side of the Vee Berth or the far end of a quarter berth and used to circulate the air. The fan draws 0.41 amps, which is negligible and the turbo blades move 2.7 CFM of air, which is a fair volume for such a small fan.
The Swamp cooler will definitely be going with me to Florida for the winter. Last winter in Marathon's Boot Key Harbor was pretty darned hot during February and March, so I think it just may come in handy.