Alcohol Stove efficiency

[James Marco]

Esbit is slightly better for heat content than alky. Theooorteically it can be better. But, that soot means you do not burn all the available fuel cleanly, soo it is about the same. It packages a bit better, carries easier and requires little in the way of stoves. The gram cracker works fine. On the down side, it is smelly and coats the bottom of the pot with a sticky soot that does not wash off easily. I am *not* Mr. Clean, but adding to the normal hiking grime doesn't seem like a good idea, though, it takes a couple days to build up enough to start getting soot around.

Hell, why even use a stove? A wood fire works well…again, sooty. And in some places illegal or not available.

WG is my choice. I carry a 17oz stove, that gets between .25 and .35 oz per liter. It burns clean. I use a bit of alky to prime it to cut down on soot. An old water bottle, recycled for use as a fuel cell, easily packs. A cap with a piece of tubing epoxied in makes a great refill kit. Mostly, I never spill any. On low, it burns a couple hours on 4oz. Enough to do 12L. Not exactly ultra light, but really efficient for long 2-6 week unsupported trips.

You can burn parafin. This is also easy to pack. It makes a good stove, but burns sooty. Again, it looses efficiency.

I have tried a LOT of burnable fuels: Xylene, acetone, unleaded, alcohols, parafins, bees wax, vasalene, deisel, kerosene, motor oil…probably a few I have forgotten at the moment. 'Corse, I have been at it for better than 40 years.

I prefer two fuels: Alky and WG. You *can* blend the two to about 10%. This has the effect of burning much hotter in an alky stove (10%WG/90% alky.) But it burns sooty. Some of the additional fuel heat from the WG is wasted in soot, but I can get ~.4oz
per pint. Not worth carrying it generally. Even if it does have higher fuel heat.

Anyway, The divide for taking alky and WG (or canister) for me is between 3-5 days. It sort'a depends on if I will be doing any fishing and extra cooking…mustard greens, fried dandelions, trout & corn bread, etc… Alky is not the best for cooking on. If I am peak bagging, it always goes. If I am out canoing, never. Like everything else in the pack, it depends on what I am planing that week.

[Brad Groves]

In most conditions I use less than a mass ounce of alcohol in my Ti Tri/Caldera. Normally a bit under 0.75 oz. Some time ago I did weight efficiency calcs & found that for my purposes, canister stoves edged out alcohol somewhere around 9 or 10 days, IIRC. The thing is, if I were doing a 14 day trip with a canister stove, I'd carry a bit less weight for the first 4 days… then I would carry progressively "more" weight (compared to alcohol) for the last 10 days of the trip. For me, an easy decision: carry less weight for more of the trip.

[John Donewar]

Hi Brad,

>>doing a 14 day trip with a canister stove, I'd carry a bit less weight for the first 4 days… then I would carry progressively "more" weight (compared to alcohol) for the last 10 days of the trip.<<

Very good point. :-)

The above quote from your last post is the reason that I plan ahead and ship a resupply box to at least one point on a 2 week / 14 day hike. Recently on another thread I was investigating if it is possible and how to ship fuel canisters ahead in these resupply boxes. I also looked at buying them locally after arriving at my starting point or midway through my hike.

Merry Christmas to you and yours, ;-)

Party On,

Newton

[Mark Verber]

> Esbit – very feeble flame, takes forever to boil. Yeah, nasty smell and soot on your pot. I don't like it : (

depends on the stove. The 8 minutes esbits takes an a caldera cone isn't too bad. Not the 4 minutes of a canister, but it's fast enough for me.

To me, "Forever" was the 15+ minutes it took for the most efficient alcohol burner I found find / mase. It used between .2-.5 oz of alcohol to bring 16oz of water to boil depending on the conditions.

The soot form esbits is really minor with good combustion. I can easy clean the bottom of my pot with a used tea bag. Obviously, scrubbing isn't required since a tea bag isn't up to that.

Yeah.. they smell. Don't last long. I won't say I have gotten used to it, but everything else works pretty well so I ignore it.

> Thruhiker says it's .25 ounce to boil 1 pint, the lightest weight stove/fuel.

that's my experience as well if I am boiling small amounts of water because the high BTU fuels also require more sustainable containers.

There is a caviet though … If I am doing a larger pot (>1L) I have found that canisters are better. I suspect that's because the small heat output of the esbit gets radiated away while a large amount of water is being heated.

–Mark

[Bob Gross]

I find it is crazy to talk about the speed of an esbit boil unless you mention the start temperature, mostly of the water. I find it to be awfully slow if I start with 35 F water, but it is reasonably quick with 65 F water.

If I am on a trip and all I have is snow melt water, that tends to be pretty cold. So, I pick up the raw cold water and leave it standing in open air for a while before I try to boil it. If the open air is 65 F, that helps.

–B.G.–

[John Roan]

FYI, I have found in my tests with Esbit, the distance from the flame to the container can make a HUGE difference in fuel efficiency and boil time. Not to be confused, an efficient boil could take a very long time (i.e. not using much fuel), and a fast boil generally takes more fuel. For me it's about finding the perfect balance or the sweet spot. The Caldera Keg-H is a great one to test different heights with since you can slide the "beer band" up and down to change the distance from the flame. But generally a low and wide pot will boil more efficiently than a tall narrow pot like the Heineken can.

To Bob's point, the elements play a huge role as well…temperature, elevation, humidity, etc. I guess this is why the subject intrigues me so much, because the "sweet spot" is so hard to find. That and we spend so much time talking about gear and not enough time talking about fuel and nutrition weights. Once you have your base weight pretty low, these other factors are the next logical step.

Just my two cents :~)>

[Mark Verber]

> I find it is crazy to talk about the speed of an esbit boil

reasonable point. My timing was for the cooler end of my "normal" conditions which is air temp of around 30F and water temp of… well I am not sure… but it's snow pack fed, so certainly not 65F.

–Makr

[Hikin’ Jim]

FYI, I have found in my tests with Esbit, the distance from the flame to the container can make a HUGE difference in fuel efficiency and boil time.

John,

In your experimenting, have you noticed a trend as to about how high your pot should be above your burning Esbit cube? I've considered using Esbit in my Caldera Cone with just putting the Esbit cube on a folded up piece of aluminum foil laid on the ground. My fear with that set up is that the Esbit would be at a less than optimal distance from the pot (too far away) although with the cone set up being what it is that may not be as big of an issue as it otherwise might be. I'm just curious if you've developed any good rules of thumb in terms of pot height.

HJ

[Greg Mihalik]

From the Trail Designs web site, regarding the use of Esbit and their Gram Cracker Kit:

"The kit contains [a] solid fuel stand set to the correct height for the Caldera Cone system, 2 side panels to control the burn, …"

Anyone with a Gram Cracker could chime in to tell you the height…

(I sold mine.)

[John Roan]

HJ,

I think there are too many variables to determine a rule of thumb for all Esbit stove setups. It seems that the type of wind screen limits the amount of oxygen fed to the Esbit, and whether you use a TD Gram Cracker or something similar to control the burn or not has an effect as well.

There is an article at thru-hiker that examines this subject, but it doesn't appear he used a wind screen, so in my opinion less than real world results. His tests show 1.25" being the optimum distance, but my testing with two different Caldera Cones shows more like 1.75". Again, my research is not complete yet so take that with a grain of salt (or Esbit).

I'm skeptical as to the Gram Cracker being "set to the correct height" for all Caldera cones, as the distance from the floor to the pot seems to vary model to model. This in my opinion is due to the newer models are made to nest inside the pot (i.e. Keg-H, Sidewinder). Maybe the guys from TD will chime in on this one.

John

[James Marco]

Actually, I spoke with Rand on this subject. He said there was some variance between the different pots and cones.

[Bob Gross]

"I've considered using Esbit in my Caldera Cone with just putting the Esbit cube on a folded up piece of aluminum foil laid on the ground."

I'm not sure that your method will get good results. I've burned a fair share of Esbit in my time, and I really think it works better to get the cube up in the air a bit. Notice that all of the commercial Esbit burners elevate the cube to at least a half-inch, and some are higher. I have one MYOG Esbit burner with the cube one inch off the ground, and it works the best for me. It seems to allow better draft.

Factors like that (draft, windshield, height, etc.) seem to make a big difference with Esbit since it is such a low-power heat source. Some people stand the cube on end instead of down flat.

If you don't have an Esbit burner that will elevate the cube, then consider taking an ordinary wooden matchbox and covering it with aluminum foil.

–B.G.–

[dale stuart]

First -I did the MYOG caldera Heinie keg without the lip/wrist band support/stopper.
I made the cone from flashing with a interlocking seam that grips the keg perfectly below the top protruding ring.
2nd – I use the Esbit brand stove, three legged fold up style.

The height of the cone is such that the now hanging keg just hits the 3 legged esbit stove supports, thereby getting optimal pot height. (At least one would think it's optimal since Esbit engineered the stove).

This has worked perfectly for me and gives possibly a better heat transfer since more of the keg is in the heated cone. Yes the keg gets dirty, I normally use some moss hanging from the trees to scrub it off – but then again replacing it is not a big deal. It's under 3oz. and it all nests well inside the keg leaving room for a weeks worth of fuel. It still works with alki if one wants to bring it along for backup.
One Esbit tab boils 2 cups easily, only hitch is having to raise the cone with the keg to pour water out. (just use a bandana to grab cone/keg where they meet.

It's been well used but here are some pics.

-Dale

[John Roan]

"I have one MYOG Esbit burner with the cube one inch off the ground, and it works the best for me."

Bob, do you have a photo of your MYOG version?

[Bob Gross]

No photo, but it is simply two rectangular pieces of titanium slotted so that they fit together in a vertical X. Then there is a large notch down from the top, and the Esbit cube is placed on a piece of perforated aluminum heat sink metal that rests on the X in the notch, and is about 1" off the ground. The perforations help with the draft from the bottom.

From the top of the cube up to the pot is the "flame height" that you want to be roughly 2". Therefore, the whole thing ends up being somewhat more than 3" tall. So, this is a titanium burner plus pot stand. The thickness of the titanium pieces will dictate the overall weight. You can take it apart into flat sheets and put it away inside your wallet.

I made mine with a hack saw. Note that titanium is extremely hard stuff to saw, so you better bring your lunch.

–B.G.–

[Greg Mihalik]

"I'm skeptical as to the Gram Cracker being "set to the correct height" for all Caldera cones, as the distance from the floor to the pot seems to vary model to model."

For most Caldera Cones the pot support height (beer band or formed rib or pot lip) is optimized for the 12-10 stove. The stove height does not change, the cone height changes. So if the 12-10 works, the Gram Cracker works.

The TD guys thunk it out.

[John Roan]

Thanks Bob, I haven't tried the air underneath thing yet. Better stop and get some more Esbit to run some more tests!

Greg, I agree, those guys are very smart! I guess I just have to see for myself.

[Bob Gross]

"I haven't tried the air underneath thing yet."

If you look at it, the titanium X keeps the heated air moving straight up against the pot, and it prevents much side-to-side air movement. Still, I only used the thing with a piece of aluminum foil around the outside for a windscreen.

If you run short on titanium metal, just run out and recycle some old Russian fighter jets. They used titanium skins.

–B.G.–

[James Marco]

"So if the 12-10 works, the Gram Cracker works."

Greg, the lower heat of the esbit means they should be set a bit higher than the alky stove to acheive the optimal heating distance.

My research on the K-Mart grease pot model, showed they set the height to the lower optimal height of the alky stove. Raising the cone a half inch does nothing to the boil times within a statistical deviation of about 15 seconds. (Same starting temp. But uncontrolled humidity for 20 test runs after a 10 test run base line was established.) The alcohol stove seems to have a larger "sweet" spot.

However, raising the gram cracker by a half inch improved the boil times significantly for 4 runs (I ran out of esbit tabs at that point) after a six run base line was run at the standard heights. Esbit was ALWAYS slower, but, burned about the same weight of fuel once I raised it. The mess, smell and time spent boiling made me drop it from further consideration, though.

At that point I was looking at minimizing boil times with an alcohol stove for a trip I was planning.

[Hikin’ Jim]

James Marco wrote: Esbit was ALWAYS slower, but, burned about the same weight of fuel…

The same weight of fuel? Hmm. Not so good. I was of the understanding that Esbit would boil the same amount of water for less fuel. In your testing you found that the weight of fuel was about the same, is that right?

HJ

[James Marco]

Yeah. For raw fuel we are talking.
After adding in for a fuel bottle it is slightly less weight, overall. But, it is not that big of a differance… hundreths of an oz.
From Heat of Combustion at Wikopedia:
100% Ethanol is 12800BTU per pound
Hexamine is 12900BTU per pound (Trioxane is fairly similar but burns slower)
After computing eutectics at 95% and the weight of a fuel bottle esbit is better, but esbit also does not burn cleanly. It produces soot and by products. It looses efficency at about the same rate, maybe a bit less. The tables assume complete combustion.

Over all, the difference between the two is mostly a matter of choice. The slower heat, set to the perfect height will give slightly better results than alcohol. At
a different air temperture, it might burn more becasue it heats too slowly, allowing heat to radiated away from the water at a faster rate. Anyway, for between 40F and 70F it isn't significantly different…maybe as much as .1oz.

My tests pretty much follow this. I could not isolate the exact distance at which esbit was optimal, not enough tablets. And I suspect that this would vary with the air temp anyway. Like alcohol, there is a sweet spot, but it is much narrower since the amount of heat is much less.

I HAD expected them to be much better. I only looked up the heat of combustion figures after the test runs because I thought I must be doing something wrong. I had assumed that they were around midway between WG and alcohol and was surprised that I could not get them to burn better. I should know better…but, it still surprised me.

Anyway, I dropped them becasue they really don't buy me enough to be worth it.
They are quite wind sensative. I often loose more than I gain. Soo, after 7-8 trips out, I just quit using them. I have several packs of fuel tabs here now, actually.

[Hikin’ Jim]

Interesting. So the weight advantage of esbit vs. alcohol is essentially negligible. BTW, did you factor the weight of the stoves into the equation? I assume that wouldn't change your calculations much.

If the weight advantage is negligible, then other factors like ease of use seem more pertinent. For me, alcohol is easier to light, cheaper, and burns cleaner. Seems like alcohol is almost the no brainer choice, yes?

HJ

[Bob Gross]

I use all sorts of stoves (white gas, butane mix, alcohol, Esbit). Mostly the Esbit gets carried along as an emergency fuel, since it is a compact solid and doesn't leak or degrade. I have one titanium Sierra cup, one butane lighter, three cubes of Esbit, and wrap that with aluminum foil, which can be a windscreen. All of that adds up to about three ounces.

If Esbit were a liquid in a bottle, I would have to keep checking on it before every trip, to make sure that nothing had leaked.

–B.G.–

[James Marco]

For raw heat, yes. Like I say, other factors seem to determine peoples choices, though.
If you cannot get ethanol (I cannot get everclear in NY) it looks a bit better. But I had access to lab stuff at Cornell, so, I could do more difinitive testing.
Methanol is not quite as good as ethanol.

As Bob was saying, for emergency use, it makes sense for a few ounces. I don't bother carrying it at all. If you have access to large ammounts of water, chemicaly treated or UV radiated, it doesn't need to be boiled, and can make sense.

If the water is already warm, around 80F or so, it can make sense.

There are a lot of variables that are uncontrolled. By the numbers, it is no better than alcohol and a lot more expensive.

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