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Preparation

Outdoorsy stuff > DIY wax-powered backpack stove

You’ve constructed the stove in accordance with the Construction page. Now you’re ready to prepare your stove for a super-remote wilderness trek. Preparation involves placing a proper battery in the supercharger and ensuring a proper quantity of properly sized wax fuel sticks.

Battery insertion
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  • Open the supercharger lid. See Photo 1, below.

  • Select an appropriate battery. See Battery, below. Press a fresh battery into the supercharger, with terminals mated to their opposite-shaped terminals on the supercharger. Close the supercharger lid.

  • While you're at it, turn the four stove/pot supports so they're flush against the stove body, for compact stowage, as in Photo 1, below.


          
       Photo 1. Preparation for packing.                                      Photo 2. Ready for use.

Selecting and packing wax fuel
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Pack your wax fuel supply in a ziplock plastic bag. One would not want wax to melt in your pack. In temperatures under 70 °F, your wax should stay solid inside your pack sitting in the sun or even in your pack sitting in a car sitting in the sun. If in doubt, double-bag your wax supply and stove, separately, and insulate them deep within clothing inside your pack. Also, stow the supercharger separate from any fuel.

If temperatures somewhere in your travels will go upwards of 70 or 80 °F, then you need to think about how high or for how long. Perhaps the most critical part of your trip, in terms of heat, will be the car ride, when you could be crossing some hot valley on your way up to the mountains. OK, so your car has AC, but you might leave your car sitting somewhere in the sun, unoccupied. Perhaps double bagging and other insulation will be adequate.

If in doubt, it may be time to consider a different wax formulation. Different types of wax melt at different temperatures. The lowest-melting-point wax (115 ºF) is paraffin, or typical candle wax. A good substitute is beeswax, with a melting point of 143 °F. It’s easy to shop online for beeswax. Another substitute would be carnauba wax, with a melting point of 180 °F. These two wax types are natural animal and plant products, and they also come with desirable burning characteristics (although I wonder if carnauba wax would be difficult to light). A good source of information for comparisons is Ross Waxes.

How much wax to pack? My tests using the stove show that 0.8 ounce of wax will bring 1 liter of water to a boil in nice weather (70 ºF [23 ºC], no wind). That’s about four 1-inch rods that fit through the stove’s stoke port. Figure you’ll need more fuel where the temperatures are lower and a breeze is blowing. You’ll need to multiply your estimated cooking needs per meal or per day for your party and multiply by the number of meals or days.

Or, just multiply the weight of petrochemical (butane, propane, white gas) fuel you have carried in the past by 2 and you should be in good shape (that's net weight, fuel only, minus containers). Alcohol is another matter: figure you can get by on slightly less wax than alcohol fuel.

Shaping wax into convenient fuel rods
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Wax fuel is best packed as rods about 1½ inches long and ⅝ inch in diameter. Check their fit using the stove’s fuel stoke port. Some candles come in such an appropriate diameter. Always yank out the wick before using any candle for stove fuel. Then, chop wax to length using a serrated bread knife. Thicker candles can be trimmed to the correct diameter using a knife or potato peeler.

If you buy wax at the hardware store — Parowax
® brand, found in the aisle with the food canning supplies — you’ll see that it comes in convenient little slabs. Using a serrated bread knife, saw (a bit) and cleave the slabs into sticks a little under ¾ inch on a side. Trim the edges to make round rods, and cut to 1½-in. lengths.

All this work and scavenging around the house for miscellaneous candle wax result in lots of scraps. I've successfully converted wax scraps into fuel sticks using a mold and by rolling thin sheets of semimolten wax. However, the fastest way I found to convert large quantities of scraps into sticks is as follows.

  • Select a baking pan with sides about 1 inch tall.

  • Using a paper towel, lightly but thoroughly grease the bottom and sides with oil.

  • Place enough scraps of wax on the sheet so that once molten they will create a layer ⅝ inch deep. This requires careful estimation. Better to underestimate and add more scraps later than for the pan to overflow.

  • Place the pan in an oven at about 275 °F until the wax is molten. Keep an eye on it. If it looks like it could overflow, then carefully remove some of the still-solid scraps.

  • Let the wax cool. While it is still warm and somewhat soft, slice and chop into sticks of the appropriate width and length. Let the sticks cool until hard.


You'll get sticks that are square in cross section rather than round. But this method is so very efficient.

Battery
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A good commercial alkaline battery (Duracell®, Energizer®, Rayovac®), inserted fresh, should power the supercharger a total of 8 hours. A lithium 9-volt battery (Ultralife®, Rayovac®) has been found to last at least 20 hours in the supercharger. You may get slightly more or less supercharger output from a battery depending on the wattage of the fan you install. A battery weighs 1 to 1½ ounces (lithium and alkaline, respectively). First-time users are encouraged to take one more fresh battery on a trip than they might otherwise estimate is needed, for a comfort margin in case of accidental overuse, shorting, miscalculation, or other user error from inexperience. Rechargeable batteries, due to their low voltage, will not dependably power the supercharger.

The amount (liters/quarts) of water that one battery can help bring to boiling can be estimated by dividing battery life (see above, convert hours to minutes) by roughly 10 minutes.

A fresh battery can power the fan in temperatures down to some 0 ºF. A weak battery in very cold temperatures could be inadequate. Warming a battery in a shirt pocket close to one's body can help by raising battery temperature to around 95 ºF.

A loose, uninstalled battery can short (be weakened) when its two terminals touch a single piece of bare metal simultaneously. To prevent shorting, a battery can be stowed separate from metals in a plastic, paper, or cloth wrapper.

Priming fluid
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If temperatures are at all cool, like below 70 ºF, then the wick could be difficult to light. If it's cold, like below 45 ºF, it can be just about impossible, I've found. Carry about 1 ounce of priming fluid. I've found that an 80-20 mixture of charcoal lighter fluid and Coleman fuel in a tiny plastic squirter bottle works well.

Disclaimer
Execute this DIY project and use any resulting product solely at your own risk.

Disclaimer

This web page and the information therein have received no input, authorization, or endorsement from,
and the author has never had affiliation with, any mentioned individual, manufacturer, or retailer.

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