re-inventing the wheel

I'm pretty lucky. lucky to have a fiance who'll wait around in a hardware store for me on a Sunday afternoon, who'll patiently watch TV while I tinker around with my stupid hobbies, and who'll then go on to celebrate with me when I'm able to boil a cup of water with my homemade stove after ignoring her for an hour.

This afternoon and evening I undertook the small project of building a soda can backpacking stove. The whole fiasco was started recently when Ngoc picked up a Mountain Hardware Phantom sleeping bag at the Mountain Hardware friends and family store, who's location is a closely guarded trade secret. This bag is made of clouds, and stuffs into a ridiculously small 15"x5" stuff sack. Think about that! Naturally, I needed to one up her w/ a cool, lightweight gadget of my own. Hence, the stove. This thing runs on pure de-natured alcohol, and weighs in at a mere ounce or two, if that. Here's the rundown of what you'll need to accomplish this feat, in purely ghetto style:

3 aluminum cans of your favorite soda: $2.49 for a 6pack
package of small razor blade: $2.49 for 5
fiberglass insulation material: $1.49 for a 10 ft. roll
1 liter of de-natured alcohol (sold next to paint thinner): $6.99

The alcohol, of course, isn't part of the build process, but you'll need it nonetheless.



The stove is based around pressure build-up of vaporizing de-natured alcohol in an almost completely enclosed cylinder. The vaporization is achieved when the can, filled w/ alcohol, is headed by an outside source. the vaporized alcohol is forced out of small openings in the can and lit to produce jets of flame coming out of the top of the can. 50ml of alcohol produces a ring of jets that last for about 10 minutes!

There is one major pitfall to this design, before you go building your own at home. The holes need to be small...small enough that only vaporized alcohol is getting out of the can, and flames aren't creeping in. If any of the flames manage to race back into the body of the stove, the interior will ignite, and boom, you have a popped can and possibly shrapnel flying in multiple directions (that's an exaggeration, it would be far from lethal w/ the tiny amounts of fuel involved). There are safer variations to the soda can stove that don't carry the risk of igniting pressurized alcohol vapors, but they are much less efficient than the pressurized version.

The stove is constructed by slicing the bottoms off two soda cans, filling one half with fiberglass insulation, and then carefully pressing them together to create an air-tight seal (try stretching the rim of one of the can bottoms by pressing a third can full of soda down tightly into it a few times). I then took a small 1.5" picture frame nail and hammered about 20+ holes into the rim of one of the can bottoms, along w/ a larger hold in the center of the top of the stove for adding fuel to the can. a penny covers the filling hole when the stove is actually lit, to keep flames from entering via the larger filling hole. Viola!

A couple other items come in handy. You will need a metal "dish" of some sort to hold a few drops of alcohol in a basin below the actual stove. The dish is lit first, and the burning alcohol in the dish warms up the stove and throws little licks of flame up the side of the stove, eventually lighting the "jets" in just about 15-20 seconds. the bottom of a tuna can, cut to leave a small rim, works fine. a few dull popping sounds accompany the lighting of the jets, and you are up and running in no time. another handy item is a bend coat-hanger for holding the pot/pan you are going to cook with. In these photos, the coathanger holds the pot much too high above the flame. Ideally, i'd prefer to decrease the distance between pot and stove by at least half.


My goal tonight was to boil a cup of water, and I was able to do so with ease! a cup of water is not a whole lot, and ideally I'd like to be able to boil upwards of 3 cups on a backpacking trip, but note that these initial tests involved 1)no windscreen 2)likely did not push the capacity of the stove in terms of amt of fuel and 3)help the pot about an inch or so higher above the stove than desirable. Keep in mind, the stove needs no circulation of oxygen...those flames are burning purely on de-natured alcohol.

Behold!



By my estimates, I was using about 45ml of alcohol per burn (3 large cap-fulls). This was good for 10 minutes, with max flame lasting through minute 8 or so. a liter of denatured alcohol, or a full nalgene's worth, would be good for 4 hrs of stove time. I think the soda can stove is great for the minimalist weekend or 1-week through-hiker, but not exactly suited for the JMT. Longer trips require a lot of fuel, and that equals weight. on top of that, I wouldn't really trust myself with only one of these in the backcountry, as the whole setup is pretty shoe-string. nonetheless, I could carry a half dozen of these stoves and they would still weigh much less than my 8 oz. Primus Classic Trail.