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Re: [at-l] Fw: soda can stove & URL

At 08:50 AM 6/22/98 PDT, WHHAWKINS@aol.com wrote:
>In a message dated 98-06-22 10:59:37 EDT, kurt@inct.net writes:
>
>> within one minute of ignition, stove
>>  is burning blue flame with just a yellow tip. Water began to have bubbles
>on
>>  bottom of pan within 5 mins, light boil at 15 mins, rolling by 20.
>
>My MSR XGK will boil a guart of water in <4 mins. What you save in stove
>weight is offset my the weight of having to carry 2-3 times more fuel.
> <A HREF="http://www.rei.com/pfc/020050405010.html">REI Product Feature
>Comparison for Stoves</A> 

I've been using a Trangia Westwind alcohol stove for a while now, and I've
found that I use very little fuel.  In addition, I built the same stove
that Kurt did, and mine seemed to burn somewhat hotter than the Trangia.  I
use the Trangia though, since I'm not convinced of the trail practicality
of this particular home made stove design.  I'll describe what I see, and
let others decide how the physics work (though I reserve the right to
speculate :-))

(1) I usually stick to one hot meal per day.  This works out to boiling two
cups of water once a day.

(2) To do that I need about one ounce of denatured alcohol in my Trangia
Westwind stove.

My total weight for one week of "cooking" is:

	a) stove 6oz
	b) 8oz bottle, fuel, and duct tape 9.6oz

I know that alcohol has about half the umph of gasoline... these are just
the results I get.  My ignition to boil time is about 7 minutes for 2 cups
of water.

So what gives?  I suspect that there are several variables in play:

(a) The heat released per unit of fuel
(b) The rate of fuel consumption
(c) The efficiency of combustion
(d) The efficiency of heat exchange to the pot
(e) The rate of heat loss from the pot
(f) The amount of fuel used in starting the stove.

How they all play together, I haven't the foggiest.  But, for the kind of
minimal cooking I do, my alcohol stove seems to do well.

-- Jim Mayer

P.S. Before someone asks... here are my issues with the soda can stove.

(1) there is no way to reclaim extra fuel.  The vermiculite holds fuel, so
the stove cannot be drained easily, and there is no way to seal the top.

(2) putting out the stove once it gets going is difficult.  The obvious
trick of laying something across the top doesn't work, since if there are
any irregularities in the way the top of the can was cut (and there will
be) flames just continue to rocket out the side.  I suppose a wet
handkerchief would do the trick, though I haven't tried that.
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