Build a backpacking stove out of two aluminum cans: design is strong, reliable, and extrordinarily lightweight, burns alcohol fuels, and can be made for next to no investment of money. Boil water rapidly, deploy a 'campfire' in the middle of your house, and amuse yourself, with a stove that weighs ten grams and costs nothing.
Step 1: Assemble your parts
You're going to need:
Two empty aluminum cans and one full one. The type matters very little, although there are some bottom-brand beer cans that are simply too thin to make a good stove; this assumes a 12 oz can although obviously the 14 oz tall cans work since I'm using one.
A single edged razor blade
Some number of thumbtacks and a nail
A piece of flue tape (ideal) or heavy gauge aluminum foil
A ruler, book, and sharpie marker
Your life will be made easier by a hammer and a pair of scissors
Step 2: Mark Burner Holes
Using the Sharpie, mark the bottom of one can with 32 holes. Start with two across, then four square, eight, sixteen and finally 32; eyeballing can give good results if done carefully.
Step 3: Puncture with thumbtacks
Go around the burner puncturing every other hole with a thumbtack, then go around again to get the rest of them. Be careful in this and other steps not to dent the can any more than necessary, handle towards the top and bottom and put pressure as evenly around as possible. The thumbtacks will bend, some of them, so you'll be going through a few.
Step 4: Add center drain holes
Take the nail and pound in seven holes in the middle of the bottom in a 'daisy' pattern. These are where the fuel drains into the chamber. The full can works fine to pound in the nail but a hammer works better.
Step 5: Score a groove
Taking the book and the razor blade, score a groove several times around the base of the can, 7/8" up.
Step 6: Cut can and peel along score
using the razor blade and scissors if desired, cut through the can near the score, and cut down towards the score at an angle. Peel the aluminium towards the score, and then along the score: it should part easily, leaving a reasonably smooth rim.
Step 7: Cut out bottom section
Using your book and razor, score the second can 1 3/8" from the base, and cut and peel along the score to make the bottom of the stove.
Step 8: Cut the middle wall
Out of the wall of one of the cans, cut a 1 1/2" by 7" strip; this can be done by scoring and peeling but scissors work better. At least one long wall should be smoothly cut.
Step 9: Fit the wall
Taking the middle strip, fit it to the inside of the top piece. Check the fit, making sure that the edge that contacts the top piece is entirely smooth. Tape down the bottom side of the middle strip with a piece of flue tape or crimp it down with heavy guage aluminum foil; flue tape is just heavy gauge aluminum foil with adhesive anyway, and the adhesive dissolves in alcohol so it won't be there long.
Step 10: Cut notches in middle wall
Three V shaped notches in the bottom part of the middle wall, evenly placed.
Step 11: Build a jig
Taking the cut off top of one of the cans, slide it over the bottom of the full can, getting it as tight as you can by pounding it against the table a few times. This lets you drink the full can later, and is used in the next step.
Step 12: Jig the bottom and join
Taking the bottom section, press it over the jig and remove. This part is tricky; lubricant would help but I confess I haven't bothered as the aluminum is just that smooth. You can get a bind but if you screw in and down then out and up without stopping you can jig it smoothly. Do NOT dent the rim at this stage; if you do, carefully smooth it on both sides with a thumbnail.
Now, put the middle piece into the top piece as before, and fit the top piece so it slides inside the bottom piece. I use a shim, made by smoothing a cut piece of can with sandpaper, to fit these pieces together. It takes practice, and is the hardest part of the project; you will really benefit from undented pieces at this stage of the game, but I've assembled some pretty sad looking pieces with a little patience. Once together, push the top down into the bottom until the middle wall engages; this often includes a 'click' noise that makes it clear that you've done the thing to the nines.
Step 13: Ignite!
You're done! Due to the double-walled construction and the integral can bottoms, the stove is much stronger than an empty aluminum can and can be expected to last years if you want it to. The best fuel is methanol, which burns blue and ignites quickly. Absolute ethanol is expensive, but denatured alcohol isn't and works well. The photos are taken with Iso-HEET isopropanol, probably 91%, which is what I had on hand; it works but burns yellow and is less efficient as the combustion continues up the sides of the pot, uselessly for heating food or water.
The stove is filled through the holes in the center, and primed by burning either a pool in the center or a little sloshed over the sides, which I find efficient. When the fuel in the chamber starts to boil, vapor rises up the side and comes out the holes, giving us our gas stove. It will burn merrily until it burns out, and with accesories you can simmer it, too; perhaps a later instructable there.
Special thanks are owed to Scott Henderson of PCTHiker and Zen Seeker of Zenstoves.net for the substantial technology behind this critter, as well as the anonymous distillers of cognac who developed it in the first place, or who are at least as far upstream as the story takes us.
The main known disadvantages of the stove are difficulty lighting in cold and windy conditions, as it doesn't carry a lot of thermal mass. A good windscreen and insulating pad would solve these problems; I have a fantasy of Jb welding a piece of aerogel to the bottom so you could fire it on ice without melting it. These stoves are favored by thruhikers, and there's just something liberating about building a 10 gram stove from dumpstered parts.