Preparation for the rugged outdoor life I intend never to lead

I never go camping, we have very reliable gas for cooking, and there are several overdue reviews I should be working on.

Super Cat mini-stove

So I, naturally, just made a little camp stove, after reading about it on Cool Tools.

It's called the Super Cat, because it's made from a small cat-food tin. Since this household goes through small cat-food tins so rapidly that I really should have made some sort of belt-feed system for them by now, the raw materials were not difficult to procure.

And all you have to do to make a Super Cat is poke some holes in said tin.

That's it. You're done.

And it really does work. Mine worked perfectly first try, getting three cups of water from 15°C to a rolling boil in about seven minutes, which is when it ran out of its first shot-glass of methylated spirits (denatured alcohol) fuel. It won't work that well if there's a breeze or it's colder, but a couple of cups quickly boiled per shot of fuel ought to be possible in all sorts of real-world situations.

It's not the safest possible cooker, of course. It'd be easy to set your camp-site, or yourself, on fire if the little tin fell over or the pot on top overbalanced. (You should rest the pot on three rocks, or make a support out of coat-hanger wire or something.) And there's no heat adjustment - it runs full blast for several minutes, then goes out.

But if you're going to cook with an improvised naked-flame device, going with alcohol for fuel is not a bad idea. It doesn't burn hot enough to instantly cook you if you get some of it on you, and you can extinguish it easily with water.

Then again, the flame's invisible in sunlight, which can be a little risky. If you see someone crash a methanol-fueled racing car then leap out and start dancing around and screaming, he may not just be angry.

But c'mon, whaddaya want from a cooker you can make in fifteen minutes by candle-light with only a nail for a tool?

16 Responses to “Preparation for the rugged outdoor life I intend never to lead”

  1. Alex Whiteside Says:

    This must've been what that guy was thinking of when he tried to make some sort of half-assed camping stove on The Apprentice. It was a can of fuel with a seperate, perforated tin can placed around it to rest a pan on. I assume that he didn't quite figure out what function the holes had, other than decoration.

  2. Chazzozz Says:

    Did you have anything else inside the tin besides a puddle of metho? When I first learned how to make these as a Scout we were always told to put a wad of cotton wool inside it first, then soak the wool in alcohol. You don't need a very big wad, just enough to cover the bottom. I must admit, we used bigger tins, too, that were about the size of the large soup cans.

    I'm not exactly sure what the wool does, but I remember the flames being not quite as intense and the fuel lasting longer than just enough to boil a small pot of water. It certainly keeps the fluid from sloshing about. Maybe it also helps the fuel to burn at a more stable rate? Someone with more in-depth chemistry knowledge may be able to comment further.

  3. daveh Says:

    It's easier to balance the pot above the burner outdoors if you knock in three tent pegs...

  4. loseweightslow Says:

    If metho is 25MJ per litre and you really did use 30ml in 7 minutes then this thing is the equivalent of a 6.4 megajoule burner. The small burner on your gas cooktop is probably 5MJ and the next one up is about 9MJ. (most cooktops that I have seen are always simlilarly sized). It's pretty good for a cheap light homemade device.

  5. Daniel Rutter Says:

    Re the cotton wool: It'd prevent the fuel from spilling, and it'd also serve as a wick, and encourage the fuel to vaporise. The Super Cat has to be lit and left to burn with no pot on it for about 30 seconds, to get the alcohol boiling. An internal wick could reduce or eliminate this period.

  6. derrida derider Says:

    Feh - it's just a simpler and less efficient version of the (already pretty simple) Pepsi can stove that's been popular with bushwalkers for decades.

  7. Daniel Rutter Says:

    On the contrary - as the Super Cat page points out, it is if anything more efficient than the fancier alcohol beverage-can stoves, boiling more water, faster, for a given amount of alcohol.

    The fancier stoves have their own advantages - more fuel capacity, for instance, so you can do proper cooking with them rather than just boil water - and the ones that run from fuel with a higher energy density than alcohol can obviously do more cooking per kilo of stuff you have to carry. But the Super Cat delivers alcohol heat to a pot about as efficiently as appears to be possible for any portable stove.

  8. Red October Says:

    I've heard that Everclear is the choice fuel for these stoves since it won't contaminate food. Lots of travelers favor it since it is very useful; cook, clean, drink, sterilze, etc. Evern works as fuel for a naptha lighter!

  9. Jonadab Says:

    Hmm... on the one hand, this has the advantage that you can set the pot directly on it (once it's going). I've never been able to achieve that with the Pepsi-can stove, even after the fuel is streaming out the jets, setting the pot directly on it causes it to go out in thirty seconds or so. So it requires a separate stand with a little clearance (an inch seems to work fine). (My guess at the reason for this limitation would be something to do with ventilation and oxygen availability, but I'm neither a chemist nor an engineer, so I could easily be wrong.)

    On the other hand, I don't know exactly how much a shot glass holds, but burning out a load of fuel in seven minutes sounds pretty fast to me. There would be times when speed is what you would want, I suppose (e.g., all you want is hot water for tea), but for my money (err, assembly time, whatever) I'd actually kind of rather have a design that burns slower and longer, even if it's a tad less efficient in technical terms. There are a number of major categories of cooking you just can't do properly at high speed. The amount of extra alcohol needed for even a 50% reduction in efficiency is just not that big a deal, compared to the weight of the food (assuming you're not relying heavily on hunting and fishing and foraging, but I think most folks who are that serious about relying on naturally available stuff would also be using flint and steel to light wood-based campfires, rather than matches to light alcohol). I've thought about a Pepsi can stove with a much smaller number of holes than the usual design (perhaps only six, or even four), but I haven't gotten around to trying it yet. I suppose a similar modification would work with this thing, though.

    On a side note, most of the sources I've seen for the Pepsi can stove insist that you want some kind of special welding tape or whatnot to seal the thing, or else you'll get large leaks; in my experience that is completely unnecessary if you put it together carefully (so as to avoid tearing &c), because of the extremely tight fit.

    I should also note that how much food-heating (or water-boiling, or whatever) you get out of a given amount of fuel is *heavily* dependent on what pan you use. Switching to a lighter-weight pan (aluminum rather than copper-bottomed steel) with a wider base (so it sticks out farther past the stove and stand) significantly reduced my fuel requirements for heating a given amount of stuff. Unfortunately it also reduced the time, which was not really an effect I was after, but as I said maybe I'll try a design with fewer holes.

  10. Daniel Rutter Says:

    Oh, that's a thought - the shot-glass is indeed not a well-understood international fluid measure.

    When I mention it above, the measure I used was one of my plethora of plastic shot glasses. They're the standard Australian "shot" size, thirty millilitres, which is almost exactly one US fluid ounce (and therefore about the same as every standard small bar shot glass). Allowing for a bit of wastage, you should get about thirty refills from a one-litre bottle of meths.

    (30ml of roughly 40%-alcohol spirits, by the way, is also one Australian standard drink. A US standard drink is 1.4 Australian drinks. So a 2.25-litre Darwin Stubby of VB, which I think you'll find is a perfectly unremarkable Australian beverage, contains 10.8 Australian drinks or 7.7 US ones. A two-litre yard of Polish Pure Spirit contains one hundred and sixty Australian drinks, or 114.3 American ones.)

  11. Jonadab Says:

    A glass that only holds a couple of tablespoons? I guess I can see why you use it to measure ultralight stove fuel. (At the risk of going wildly off-topic, the absolute smallest thing we'd ever call a "glass" around here would be the notional eight-ounce "glass" nutritionists use to tell you how much milk you should drink, but any real glass I've ever seen would hold 12 fluid ounces plus ice without spilling; 21 and 32 are more common sizes; 48 and 64 ounce glasses exist. Anything below 12 ounces would be a "cup", not a "glass", and even then the smallest I've ever seen was a six-ounce baby cup with a sippy top. One ounce? Cough syrup lids are larger than that. What would you drink out of something like that, straight vodka?)

    So anyway, two tablespoons of fuel in seven minutes does sound very comparable to the standard Pepsi-can stove. A touch faster, perhaps, but comparable. So, fine for boiling noodles, but not exactly what you want for cooking rice.

    It occurs to me is that a smaller-diameter burner might be a better option than fewer holes, because it is desirable to have a full ring of flame so that fuel rising in the middle passes through the flame and is burned.

  12. Daniel Rutter Says:

    Jonadab - I know you're a Christian, man, but you live in Ohio, not Utah. You really ought to at least know what a shot-glass is :-).

    (Reminds me of the Jehovah's Witness who asked me what day Christmas was. I told him "You're allowed to know.")

    What would you drink out of something like that, straight vodka?

    Yes, that is the usual procedure.

    I think you'll find there are one or two other beverages of similar strength.

  13. Jonadab Says:

    Alcoholic beverages in Ohio, I'm afraid, are mostly beer. In the upper income brackets some people get into wines, but I only know a small handful of people in that category (e.g., one set of cousins on my dad's side).

    Yeah, I know there are other strong beverages than vodka. But that's not the point.

    My understanding was that people generally mixed vodka (and other things like it: scotch, jack, tequilla, anything distilled, really) in with other stuff, like orange juice or something, to make it more... potable.

    Other than some kind of twisted hazing ritual, I have difficulty imagining the line of thinking that would lead someone to want to consume it unmixed. That would have to taste remarkably terrible, I should think, even to someone who is accustomed to alcohol. I mean, I like sweet and sour as much as the next person, but I'm not drinking vinegar straight.

  14. Jonadab Says:

    Okay, this is only tangentially related, but it's useful information, so here goes. After some trial and error, I can report that a Pepsi can simmer-stove is very achievable, though not *quite* as easy to build as the standard model.

    Diameter is indeed the key. The size of the central hole has a strong impact on the burn speed (a larger hole yields faster fuel consumption and more heat output per unit of time); drawing around a US quarter gives you a good basic simmer. Put the ring of small holes about an eighth of an inch out from the edge of the central hole (yes, this means they will be on the inner, concave portion of the can bottom), and the wall that separates the central ignition chamber from the outer evaporation chamber goes between the central hole and the ring of small holes. With the quarter-sized central hole you want a ring of about eight pushpin holes. The tricky part is getting the height of the separating wall right, but if you make it too tall you can measure how much you're off by on the outer edge of the partially-assembled stove (the top and bottom halves won't go all the way together), push it apart, trim, and reassemble. (I used a wire twist-tie to hold the wall cylinder at the desired diameter while doing this.)

  15. Jonadab Says:

    Err, did I say a ring of eight pushpin holes? I meant twelve.

  16. violet Says:

    Other than some kind of twisted hazing ritual, I have difficulty imagining the line of thinking that would lead someone to want to consume it unmixed.

    Well, it's not always entirely unmixed. For example, I like my tequila shots with a bit of Tabasco sauce. Tastes like curry.

    And it's not hazing (well, it's not always hazing), so much as it what we might call a community-building experience. You and your friends get your shots together, down them together, and then grouse—together—about how you really should have sprung for the good stuff and why didn't you stop drinking this shit in high school? Then the warm fuzzies set in, and more shots are poured.

    At some point, tradition dictates that you will pass out in an extremely uncomfortable position, generally on top of or near a pile of (living) bodies. This may or may not occur after an unwise sexual experience with one or more of your friends, which was probably life-changing and incredible, if only you could remember it. In the morning, there are eggs.

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