A simple alcohol stove more fuel effecient than the Jim Wood Super Cat?

"> A very interesting article you wrote on OM. What would happen if you started with a 450g canister rather than a 230g canister? What would happen if you only boiled 1 liter per day (500ml morning, 500ml evening) which is a little closer to my actual solo consumption."

"The gas vs meths consumption one? Derek Goffin's comment about the canister's contribution to each 'burn' gives you a clue; divide the weight of the canister by the number of burns you get from it, and add that to the amount of fuel per burn. That gives you the total fuel & container mass per burn. The amount of water you boil per burn is largely irrelevant, as the same energy is required for either fuel. Think of it as 'longer days'; it's a scaling factor."

Well, not quite. His primary analysis revolves around a 230g can. If you change the canister to 450g, you need to also reduce the can weight. from around 110g to about 175gram. This will change the originol comparison, provided you are out long enough to completly use a can. I found I would typically use a full 8oz can and a 4oz can in a weekend hike (two nights) with 4 people. This was simply too expensive to support for 12-18 weekends per year. Now that the kids are gone and the wife cannot get out due to knee problems in her old age, I will have to check again. But, the SVEA seemed far better when weighed against the expense of canisters at the time.

> Well, not quite. His primary analysis revolves around a 230g can. If you change the canister to 450g, you need to also reduce the can weight. from around 110g to about 175gram.

James, I'm not sure if you're reply to Jim, or to me. If you're replying to me, then the 'him' you're referring to (the OP in the linked OM thread discussing gas vs meths usage), is me, aka captain paranoia…

Yes, if you change canister size, then the relative mass of canister compared to fuel becomes less, due to the square law vs cube law growth of surface area and volume.

If you use a larger canister, then, using Derek's approach, the mass of container you need to add to each burn is reduced, and you'll start to 'break even', and gas will eventually be lighter. Whether this break-even point comes within the duration of your trip (or re-supply points for extended trips), depends on your trip length and fuel usage. 450ml canisters are certainly bigger than I need for any trips that I can manage to get away on; they'd probably last me about two weeks…

The rate of fuel use (i.e, volume of water boiled) is only significant in terms of the size of canister you might need for a trip. For a given canister size, it has no bearing on the analysis.

If you'd like the spreadsheet I used to play with the numbers, drop me a PM with an email address, and I'll send it to you.

Hi Kevin,
You wrote:
"If you use a larger canister, then, using Derek's approach, the mass of container you need to add to each burn is reduced, and you'll start to 'break even', and gas will eventually be lighter. Whether this break-even point comes within the duration of your trip (or re-supply points for extended trips), depends on your trip length and fuel usage. 450ml canisters are certainly bigger than I need for any trips that I can manage to get away on; they'd probably last me about two weeks…

The rate of fuel use (i.e, volume of water boiled) is only significant in terms of the size of canister you might need for a trip. For a given canister size, it has no bearing on the analysis."

I agree. But the weight of what I carry in my pack is a concern when I go backpacking. I typically head out for a week at a time. I usually boil around 2-3L per day. With the instant off/on of canisters, this is it's only advantage over alcohol. The heat content is roughly the same *counting the canister*. Canister stoves also represent a step function. The *least* I can carry is one small can. Or one large can (or any combination.) This results in a step function. Note that the graph as presented was incorrectly drawn. . .no biggie. In a kitchen it doesn't really matter. On my back, it does. Also the relationship between weights of canisters is different. And, since I will be carrying them the full distance of the hike (assuming no resupplies), then I will also be carrying about 50% of the fuel weight as dead weight.

The approximate ratio of the weight of a 4oz can/4oz of fuel os 50/50, ~50%.
For an 8oz can this ratio changes to about 75/25 fuel/can. or ~67%.
(Depends on the maker of the can and fuel.)

Between the step function of container vs fuel, and, fuel vs consumpion. They are about a wash. Worste case is having to bring a nearly empty container for one more day. This could approach a 7% ratio fuel/can. Not good on my poor tired back. But, we are only talking 4oz difference. Really not that bad.

Divided over the whole trip, however, the can weight really tells. You always carry it. Not a simple 1oz bottle. Soo, between tailering your initial load to your consumption(about the same on a "perfect" trip) and the much faster reduction in weight over the course of the trip (my cut off is 5-7 days for using a canister) and the step functions for using them and the dead weight over the duration of a trip, I cannot in good conscience recommend them. YMMV depending on your usage. I drink a lot of coffee in the morning (4-10oz cups) and soup/stew & cocoa for supper.

Hi James,

I'm afraid I'm having trouble determining if we disagree or agree…

My OM thread was an observation of how fuel system weights compared between meths and gas, and considered the mass of the fuel containers: heavy steel for gas, light plastic for meths. It also considered the step change required to take a gas canister for any trip duration (assuming you started with a full canister; you can, of course, start with a partly-used canister).

For the gas and meths usage I've found with different stoves, the analysis seemed to show that, for the 230g canister, the gas system was never lighter. So, for my usage (length of trip, fuel used per day), meths is always lighter, so I carry meths when weight is a consideration. With a 450g canister, gas may be lighter at some crossover point, but it's more fuel than I'd ever need on the trips I do.

> But the weight of what I carry in my pack is a concern when I go backpacking. I typically head out for a week at a time. I usually boil around 2-3L per day. With the instant off/on of canisters, this is it's only advantage over alcohol.

I'm reading this to mean that, like me, you prefer alcohol on the basis of weight, right? And to save your back, you use meths, and not gas? If not, then I'm confused…

It may be that you've misunderstood my comment about fuel use/water boiled. I didn't mean that to be a statement that I don't care how much fuel it takes to boil some water; I meant that fuel usage and water boiled are interchangeable measures (assuming some fuel efficiency that is fixed for a given stove system). I'm always striving to be fuel efficient. If someone needs to boil lots of water/do lots of cooking, the only effect it would have on the graphs I posted on the OM thread would be the slope; they'd be steeper, but they'd keep the relationship that showed meths always being lighter.

> Soo, between tailering your initial load to your consumption(about the same on a "perfect" trip) and the much faster reduction in weight over the course of the trip (my cut off is 5-7 days for using a canister) and the step functions for using them and the dead weight over the duration of a trip, I cannot in good conscience recommend them.

I think we're agreed, then; we would both recommend alcohol as the lighter system? That was certainly my conclusion on the OM thread, which brought out all the 'but what about ease of use, blah blah blah?' comments…

Anyway, back to your other interesting post that I missed earlier…

> At, 1/3ounce? That is good efficiency for alcohol. This seems to be the best case for fuel efficiency.

That's very good efficiency. Assuming it's 95/5 ethanol/methanol, it comes out at about 82% heat transfer efficiency (using the lower heating value). I think I do well if I achieve 65%.

> I can do only slightly better with the SVEA.

Which SVEA stove? Surely not boiling 2 cups (474ml) of water on 3g of alcohol (that would be 250% efficient…)

> The Coleman F1 does a bit better at about 3 grams […] Both boiled in about 4 minutes.

A 4 minute boil with 3g of gas (Coleman F1) is very impressive. Again, that would seem to be more than 100% efficient: 474ml of water from 15C to 100C takes 169kJ; 3g of propane LHV is 3*48.8 = 146.4kJ.

I'm sure I must be mis-reading you in some way.

> Roughly, holding my hand on top is a guide to how much waste heat is being generated.

That's the method I use, too, and have suggested for people trying to choose a burner to use with a clone; there are fast, hot meths burners out there, but they seem to be inefficient (see my earlier comments about stove system efficiency).

> Heating quicker wastes more heat, but prevents so much heat loss. Heating slower increases rediative heat loss, but increases efficiency. Soo, again, the ultra small burners were failures due to the entire *system*, not so much because of the heat generated.

Yup; heat too slowly and the radiative losses will overtake the 'escaping hot gases' losses bringing the efficiency back below a hot & fast system.

> A caldera cone works well, but wrapping it in fiberglass insulation would help and not weigh that much.

It's not something I've tried; I have put a piece of Thermawrap (Reflectix) on top of the pan, but didn't find it helped much, but I may not have been using a burner slow enough to benefit.

> A larger heating area on the bottom would also allow for faster heating, as well as increased efficiency.

Yes; a large area pan is essential for burners like the White Box Stove, which burns hot, and has a wide flame ring. With a smaller pan like an MSR Titan, it's rather wasteful.

> A heat exchanger on the bottom and lower sides of the pot will also help.

I tried using the JetBoil pan with a meths burner, but found it increased the fuel usage. Which I figured meant that it was actually acting as a radiator, dissipating heat to the environment, rather than sucking 'waste' heat from the flame. I heat exchanger is only useful if there's waste heat to pull from the flame, and for a low-power burner, that may not be true, in which case, we're back to the case where radiative losses dominate.

CP SAID
"I tried using the JetBoil pan with a meths burner,"

Presumably this means a short windshield (c(l)one) is needed to protect the heat fins from wind so that they work as expected. Could presumably stop just above said fins.

Actually, I think such a shield would make sense even for gas jetboil, when windy.
For said gas mode: could hang from 3 loops on the neoprene cozy.

I have been doing some experiments with alcohol stoves and Jetboils and believe that the efficiency of the heat exchanger is lost with most alcohol stoves. I believe that the alcohol flame is a very low energy (velocity) flame. The gap between the heat exchanger fins are very small and create a high drag. I suspect that a lot of the heat is flowing around the heat exchanger rather than going through it. With cartridges, the burn rate is very high and I believe forceful enough to drive exhaust gasses through the fins. It would be nice if there was a way to capture the thermal image of this. My 2 cents – Jon

"I'm reading this to mean that, like me, you prefer alcohol on the basis of weight, right? And to save your back, you use meths, and not gas? If not, then I'm confused…"
Yes, quite so. However, with larger canisters, the step function does indeed cross back and forth. A LOT depends on your usage, and, blende of fuel. It really matters not. Canisters never really do that much better. But it seemed to me you had added in for one canister and used it up, ie, a perfect trip. Adding in a partially used canister only makes things worse. My usage is quite high and is likely to remain so in my sleepy years. I am retired. and my kids are in their 30's these days. So for between 1-4 nights out I prefer alcohol. After that I like WG.

"I think we're agreed, then; we would both recommend alcohol as the lighter system? That was certainly my conclusion on the OM thread, which brought out all the 'but what about ease of use, blah blah blah?' comments…"

Absolutely! Out solo, on fast moving UL trips, that is the way to go.

Yes

Have you considered a passive (similar to an alcohol stove), white gas stove as a way to reduce weight? They tend to smell alot, but they do use less fuel per cup of water boiled. Best regards – Jon

> At, 1/3ounce? That is good efficiency for alcohol. This seems to be the best case for fuel efficiency.

"That's very good efficiency. Assuming it's 95/5 ethanol/methanol, it comes out at about 82% heat transfer efficiency (using the lower heating value). I think I do well if I achieve 65%."

Actual usage was closer to .36-37 as I remember, I called it about 1/3ounce. This was clinical grade ethanol used at the Cornell labs, near 100% except for some trace elements (benzene, toluene, etc.) Likely from the petrolium industry and quite hydroscopic. Rand at Trail Designs might have a copy of some of the tests.

Roughly, the SVEA uses just over 1/2 of the fuel that the alcohol stoves do. My computer crashed about a year ago and I lost most of my data. As I remember the best I could do was .28oz per qt. with a standard pan. 10 runs varied up to .35ounce. This was with an improved heat exchanger and cone heat trap on the pot. This was better than what would get in the field, of course, but close enough to max efficiency not to bother with more. 250%, impossible. This is what decided me to bring the SVEA out for 6 weeks on the NFCT.

The coleman was treated the same way. It performed rather well also. Again with a heat exchanger and cone on top of the pot. This was fiddly at the low setting, though. Again, 100%…I don't think so.

If I ever get some free time, I'll have to retest again…

> Absolutely! Out solo, on fast moving UL trips, [alcohol] is the way to go.

Right, now I think we're agreed ;-)

> However, with larger canisters, the step function does indeed cross back and forth

Yes, that's exactly what happens. For a given cylinder size, the rate of use has no effect on this step function crossing; it merely changes the slope. Changing the cylinder size alters the step function crossover. The weight of the burner also influences this, too (i.e. total system weight).

I liked your observation about the total weight falling quicker with alcohol stoves; that's something I'd missed; I'd only considered the original starting weight. So not only is the starting weight often lower, the average weight is even lower.

> Roughly, the SVEA uses just over 1/2 of the fuel that the alcohol stoves do.

I'm now guessing that you mean the SVEA 123 pressurised liquid fuel stove. SVEA have also made alcohol stoves, too (the "Swedish Army 'Trangia'" is actually a SVEA, or at least, my one is…).

> 250%, impossible.

Yes, that was the point I was making, and why I asked for details; the numbers didn't add up to me.

Petrol/gasoline has a lower LHV than propane, so I don't see how either a SVEA 123 using 3g of gasoline, or a Coleman F1 using 3g of propane, could boil 2 cups of water from 15C to 100C; as I said, it would be in excess of 100% fuel efficiency, which, as you agree, is impossible. I can only assume that my assumption that you used a 'standard 2 cup (474ml) load' for these tests is mistaken, and that you used a smaller volume of water for the tests.

Jon Fon wrote: [passive white gas stoves] do use less fuel per cup of water boiled.

Do you have a passive white gas burner in mind? I've never seen a passive (i.e. non-pressurised) gasoline burner that wasn't very sooty and smelly. I don't like soot…

I made a non-pressurized white gas stove a while ago (YouTube Cone Zone white gas stove -http://youtu.be/L4hvOH4586Y) and I think Zelph made one as well. It boiled 2 cups of water using 12 ml. and generated no soot on the pot. It does smell a bit along the lines of Esbit. It was never optimized and I dropped it because people seem to think that carrying white gas was not the best option (~15 minute time to boil). I know a lot more about stove and would guess that I could bring the time to boil down to the 8-10 minute range. I suspect that the fuel efficiency would get better as well. If there is sufficient interest, I might consider tweaking the design, however; it would still smell and you lose the safety of carrying plain DA. Best regards – Jon

Thanks, HJ. After posting, I realized that I'd probably be saving weight regardless. Nice to see your numbers though being that I can be lazy that way.:-)

Kevin….in the link you posted "Make Your Own Meths Burner", is that a 500ml Fosters can? So far, all I've been able to find in Fosters is 750ml. Sorry if this has already been covered but can other 500ml cans be used with those same directions? I only ask as I haven't paid any attention to the shape/design of cans.

rusty

Interesting discussion(s)!

Rusty, you’re welcome.

Kevin, thank you for injecting a little science based rigor.

Jon, got any more photos of that passive white gasoline burner? I can’t quite tell what I’m looking at.

HJ
Adventures in Stoving

HJ – the link was in the posting http://youtu.be/L4hvOH4586Y

Jon

Whoops, missed it. Thanks, Jon.

HJ
Adventures in Stoving

A very interesting stove, Jon. Good video. Gave me a good idea of what the stove is.

Not sure how I feel about an open gasoline stove. Very interesting though that it can burn with a blue flame and not a lot of soot. Quite a trick there.

And your similar stove for IPA, it also burns with a blue flame? How much does one of your cone stoves weigh?

HJ
Adventures in Stoving

HJ – I will probably make one up this week based on the isopropyl stove. It will probably weigh 30 gms. I still don't know if the stove will be practical or of any interest.

Jim wrote: "Kevin,thank you for injecting a little science based rigor."

I can't help it; it's my job… And, as I said earlier, there's no point comparing apples and oranges. Without rigour, you can't make informed choices.

Jon,

That's a nice-looking burn from white gas. Very interesting, and very simple design. I might have a play this weekend…

The problem with YouTube is that there are so many stove videos to watch, and weeding the good ones (and there are some brilliant ones) from the mundane or downright useless is difficult. Yours look very interesting :-)

I also like things to be organised (maybe I should have been a librarian rather than an engineer), and YouTube seems to be rather random, relying on serendipity, rather than directed search.

Rusty,

Yes, you can use just about any cans to make the burner in the OM article; Fosters cans were just what were lying in the street. They don't need to be 500ml, either, 330ml is fine. It's best to get two from the same manufacturer, though, so the sizes are the same (so cans by the main can manufacturers: Ball, Rexam, Crown, CP, etc.). As you may be able to tell, I've spent a lot of time (too much) looking at cans…

Then, when you've got the hang of the techniques, move on to the 250ml Rexam (red bull) cans, as, like Jim, I find this size burner well suited to efficient use with small backpacking pans.

"> Roughly, the SVEA uses just over 1/2 of the fuel that the alcohol stoves do.

I'm now guessing that you mean the SVEA 123 pressurised liquid fuel stove. SVEA have also made alcohol stoves, too (the "Swedish Army 'Trangia'" is actually a SVEA, or at least, my one is…).

> 250%, impossible.

Yes, that was the point I was making, and why I asked for details; the numbers didn't add up to me."

Yes, I have been working on a kitchen and have been too busy for any retesting. I will simply say to retract all results to do with the SVEA and Coleman stoves. Mostly, I was just relying on memory. It seems to have failed along with the rest of my body…

My apologies to all.

HJ – I will probably make one up this week based on the isopropyl stove. It will probably weigh 30 gms. I still don’t know if the stove will be practical or of any interest.

Hi, Jon,

Just how bad does it smell? Does it make the food smell?

And you were using 12ml of fuel to boil 500ml of water? Is that correct?

Does it ever flare or get out of control?

HJ
Adventures in Stoving

Jim wrote: “Kevin,thank you for injecting a little science based rigor.”
I can’t help it; it’s my job… And, as I said earlier, there’s no point comparing apples and oranges. Without rigour, you can’t make informed choices.

Agreed and much appreciated.

…move on to the 250ml Rexam (red bull) cans, as, like Jim, I find this size burner well suited to efficient use with small backpacking pans.

My interest dates back about a year and a half when I became dissatisfied with my Super Cat, which I have found is NOT efficient. I know others have had different experiences, but that’s my experience with the 780ml ti pot I was using. The problem with a side burner like the Super Cat is that the flames go up around the sides of the pot and are wasted.

I did a series of experiments with a wide variety of designs. My interest was to find a burner that didn’t send flames up the side of a small pot. That interest led me to the smaller cans which, with the right design, seem to work quite well with smaller pots, pots of the type used by the solo walker/solo hiker.

HJ
Adventures in Stoving

Addenda to the above post:

My 780ml Snow Peak pot solo alcohol set up:

Things fit nicely inside. Included are a BPL Ti windscreen, alcohol measuring cup, a small folding cup, a small bottle of alcohol, a Bic lighter, and the Super Cat stove.

Preparing soup on my set up:

Set up in use:

Set up after use. Note Super Cat inside.

HJ
Adventures in Stoving

Jon: what about an open kerosene stove— safer than white gas?

Sorry about not responding in a timely manner. First, my observations about white gas, with the CONE Zone design it smells stronger than Esbit. If I re-design it along the lines of my current isopropyl stove (to speed up the time to boil), I think that the extra ports will also reduce the smell. White gas stoves are sensitive to the wind; slight breeze will cause the stove to burn yellow and create soot. I tried kerosene once and it scared the crap out of me and I don’t plan to pursue this. Zelph (Dan) has kerosene stove that he is working on and I would follow his development. Best regards – Jon