Wax burners
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Since I'm heading out the Aleutian Islands again and there is only jet service to Adak (TSA inspections, no liquid or gaseous fuels), I fiddled with some solid fuel options. Yeah, I know Esbit is solid (although I haven't checked into its transportability), but I wanted to check into some cheaper options – stuff I'd throw away on site if I'm hauling lots of caribou meat back.
After I mentioned this, Jerry pointed out there are an earlier thread:
http://www.backpackinglight.com/cgi-bin/backpackinglight/candle_stoves.html
that gives a lot of helpful thoughts and data.
I did a girl-scout-style spiraled-cardboard wax burner. My fuel efficiency wasn't quite as good as in that 2008 posting, (I used 9 grams of wax to boil 300 grams of water) but it was my first attempt in 45 years (since I accompanied my mother and sister on Girl Scout outings). At one-minute intervals, I measured: Time=0: 61F, 73, 86, 104, 118, 130, 141, 152, 161, 176, 191, 202F (@ 10 minutes) and I stopped it there. The burner weighed 9 grams less afterwards. There was some soot on the pot – more than with Esbit or any WG stove, but less than with wood.
I did my testing inside the garage, simply covering the burner with a can avoided excessive fumes.
Cost tip: Go to Goodwill and look for a few one-pound candles for $0.25 each. Those BTUs are 1/12 to 1/40 the price of propane and butane canisters. Of course, the wax is "winter berry" scented and maroon in color, but WTF.
My first run used cut-down soup cans and tuna cans. I've got some cut-down aluminum soda cans set up for the next pour. Thick-wall steel to thin-wall aluminum makes a difference. The bigger variable I'm going to play with next is reducing the amount of wick. And annular containers.
Here's how I suspended the small can within the large can. It worked pretty well:
And here is the set-up. I used a "church key" can opener to make a series of air holes in a steel can. That was quick (and cheap).
Short answer: don't.
While a self-lighting charcoal briquet initially heated water faster than a wax burner, it was due to the burning off of volatile petroleum chemicals. A one-minute intervals, I measured: Time=0: 60f, 74, 97, 117, 133, 151, 165, 174, 182, 187, 188 (at 10 minutes). Clearly something had failed / dropped off. Examining the briquet and the flame, it was slightly glowing as the carbon burned, but the volatiles were all gone. The briquet went from 39 grams to 29 grams for a delta of 10 grams BUT the 29 grams remaining wasn't very useful unless you needed only to warm something. So I'd call it a fuel weight of almost 39 grams.
It weighs more, costs more, and I'm not sure you're allowed to fly with self-light briquets, so I"m going to fine-tune the wax burner. The briquet had a higher initial heat rate, but any holder of volatiles would have.
Thanks for the interest. The annular air space really helped. The first pic is of the annular burner on the workbench (i.e. the air passage is blocked). Not visible in the photo is a lot of whitish wax vapor down near the base of the wick, some of it spilling down the annulus, much of it, I suspect, contributing to wax loss without heat and soot.
The next pic is seconds later with the burner elevated on two sticks to give air flow up through the annulus – the wax vapor gets pulled in the flame, burned, and the flame takes off – I suspect on little if any more wax consumption.
So I liked the annular burner much more than the solid-bottomed ones. I liked the smaller wick amount – that in and of itself made for less soot and smoke. I really liked the sturdiness of the fiberglass wick.
I wasn't so keen on the need to support it on two sticks. That's easy on my workbench with 1x2s laying around, but would be harder to do well on rocks. Potentially, two metal cans could be used – one as the pot, the other, larger diameter one as a shroud, burner support and pot support by running wires across the larger can. Ti tent stakes come to mind as supports. But I also wanted something with a larger wax reservoir because this first, narrow one was tricky to refill.
So:
In front is 2G – the one burning in the post above. Annular air gap – good. Narrow annulus – not ideal. It is a narrow energy drink aluminum bottle section J-B Welded to the bottom inch of a beer can. Then I drilled out the annulus.
In the right rear is 3G – the same narrow energy drink can JB Welded to a larger, Foster's AL can bottom. It gives a LOT more volume for wax and shouldn't need to refilled so often and could be refilled with bigger chunks when it does (free crayons restaurants give to kids to color with?). It still needs a hole drilled through the middle, but the design evolved.
Left rear is 4G – tuna can with 1.5" hole cut in it and the tapered portion of the energy drink jammed in and then JB welded. I liked how snug it fit when pressed in – nice to start with a better mechanical connection before the epoxy was applied. Big annular space for more wax and easy refills. And I extended the small energy drink can down to create three legs so the burner is self-supporting off the ground. Details on the legs to follow.
So the energy-drink can was pretty sturdy – much thicker than a beer or soda can. But still, those three legs felt a little flimsy, so I back them up with another layer of aluminum (just cut strips from the same can so they even had the same curvature). Some JB weld and a clothes pin on each one and they really made the legs a lot stronger. It doesn't pack down as well, but it eliminates the need for perfectly sized rocks in the wilderness. I'm waiting for the JB weld to fully cure, then I'll add fiberglass wick and wax and test it. To do it again, I'd extend legs down from the OUTER can so as to give a bigger, more stable base.
Kind of low-res images, I know, but I run them through Facebook. At least they should load quickly at 10-50KB each instead of 1MB.
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