John, Thanks for this posting. Very timely. I'm hoping to get another month of sailing up here in the northwest, but nights in the 30's and days in the 50's make it pretty chilly. Looking forward to seeing the details on the Sterno heater you're building.
By the way, saw some pictures of your old cat boat. BEAUTIFUL! Larry On Fri, 28 Sep 2007 22:03:45 -0500 John R. Butler <[EMAIL PROTECTED]> writes: > Perhaps this excerpt from an article I wrote about heating systems > for boats may summarize some of the many contributions on the > subject. My article was published in "Sail" in Sept 1977 and > "Motorboat" in October 1977. > > One caution that should be common knowledge which always > bears > repeating: never use an unvented combustion-type heater in a closed > > cabin. The fire uses oxygen, the same as people do. People go to > sleep with such a heater on. The heater uses oxygen. The oxygen > level > goes down. The heater cant get enough oxygen. The combustion > process > puts out carbon monoxide. The people begin asphyxiating. Their > central nervous system tells them to breathe more deeply. They do. > > They breathe in huge gulps of carbon monoxide. Then they die. The > proper solution to this fatal possibility is a properly vented > system. > Many fuels produce water vapor as a combustion byproduct, > and an > unvented heater aggravates the dampness aboard a boat. On the other > > hand, a properly vented combustion heater dries the air. As air is > > exhausted up the chimney, fresh air is drawn into the cabin. As this > > air is warmed, its relative humidity decreases. This drying effect > is > actually typical of any heater which causes fresh air to enter the > > cabin even when the outside air is damp. > If cool, damp outside air is warmed up, the water vapor is > > dispersed in a larger volume of air and the air feels drier. Look at > > tables 16 and 17 in Bowditch. If the outside temperature is 50 > degrees and the relative humidity 100 percent (saturation, visible > > mist), warming the air to 74 degrees will drop the relative humidity > > to a comfortable 43 percent. A boat cabin probably wont get that > dry, as the outside air will mix with the humid inside air and > ng and cooking will add moisture to the air, but the > difference will be noticeable and pleasant. Solid fuel stoves will > > make a greater difference because they use more air but they also > use > more fuel, given their chimney loss. However, the lower cost of wood > > or coal makes that greater fuel consumption acceptable. > Unvented heating systems, such as some electric systems, > will cause > an initial drying of the air as the cold damp cabin is warmed, but > > when the temperature stabilizes and breathing and cooking add > moisture, the humidity rises. Then when the temperature is lowered > at > night for sleeping, the cooling air cant hold as much moisture and > > the humidity reaches the saturation point. Then water condenses on > > ports, overheads and the inside of the hull. The dripping calls for > > dehumidifying. > > John R. Butler > [EMAIL PROTECTED] > > > > _______________________________________________ > http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats > > _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats
