October 27, 2013

How much heat you need

WHERE I LIVE, it’s the season of spiders’ webs and cold, clammy fog.  The silky glistening strands whose presence is revealed by the condensed moisture remind me that this is also the season when boaters need to start thinking about on-board heating, if they haven’t done so already.

If you’re starting from scratch, how can you find out how much heat you need?

Well, you can estimate pretty closely the hourly amount of heat you need for a cabin by multiplying the volume in cubic feet by a number varying from 10 to 20, depending on how fiercely cold the winter is in your area. The result is expressed in British Thermal Units, or Btu/hour.

In sub-tropical Florida, for example, the number would probably be 10; in southern California it would be 12 or 13; Washington state would rate about 15 or 16; and New England would be about 20.

For example, let’s say you have a cabin measuring 10 feet by 8 feet by 6 feet. That’s 480 cubic feet.  If you lived in San Diego (number 13) you’d need a heater capable of putting out 480 x 13 = 6,240 Btu/hour.

If you lived in Maine (number 20), your heater should be capable of producing 480 x 20 = 9,600 Btu/hour.

If you take it into your head to cruise all over the place, you should probably work out the coldest climate and the length of time you’re likely to be there, and make some sort of compromise.  There’s not much point in having a big, fierce heater if it’s not used for the majority of the time.

Very small boats might prove an exception to the formula rule expressed above. I have cruised on boats so small that a Coleman pressure kerosene lamp was adequate to heat the cabin and dry out our soaked underwear as well.

Don’t be tempted to use a household kerosene heater, though. They are too easily tipped over on a boat and they produce enough carbon monoxide to kill you.  Remember that carbon monoxide is present wherever there is an open flame or an engine exhaust.  If your source of heat is gas or kerosene you should either make sure to open a porthole or companionway slide to admit fresh air (and thereby cool down the cabin, which seems to defeat the whole object of the exercise) or have a proper smoke stack to dispose of the fumes laden with carbon monoxide.

Finally, if you have no heater, or your source of heat fails, try rum. If your insides are toasty warm, it hardly matters how cold the surrounding air is.

Today’s Thought
We have all sinned and come short of the glory of making ourselves as comfortable as we easily might have done.
— Samuel Butler the Younger, The Way of All Flesh

Doctors keep telling us that exercise kills germs. But how do you get the pesky little things to exercise?

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)


Jack said...

Love the sound of my old Coleman Lamp....Yes, sound. It was/is one on the most therapeutic sounds at night...So much so, I take it in the R.V. and use it instead Electric.
Lamp on' a good page turner with a single malt in a "proper" cut glass tumbler.....God inspired.
Try it sometime,

Imke Feldmann said...

Hi John,
Always enjoy your blog but there are several points about your heat post. All fuels produce CO if there is incomplete combustion, even a Coleman lamp. You rightly point out that there must be sufficient inflow of oxygen to allow complete combustion. Second, burning kerosene always produces moisture, and thirdly drinking alcohol when cold is really dangerous if you are not in a warm environment. But I suspect you knew this.
Keep blogging in spite of anal retentives like me.
Yours aye,

Jack said...

Opps, the thought police have moved into your blog......Remind me to sail a wide path of Bill. I'll be afraid of breathing in and out if I have to read this crap......
Sorry Bill, I'm sure your world is a far safer place.....Just don't invite me over anytime....anal or not
GMT Jack ....

biglilwave said...

I always thought the best alcohol stove is the human body.