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  1. #1

    Default First Timer with a question about Alcohol Stoves

    Hey everyone!

    Greetings from Scotland!
    Thanks for welcoming me to the forum.
    I've been following it for some time, and there are some amazing projects up on here!

    I've noticed a lot of people have really diverse backgrounds in science & engineering, so I have a question I've been wondering about for some time:

    I love Alcohol Stoves, and there's lots of interesting discussion about boil times etc.
    Does anyone know what the theoretical FASTEST boil time would possibly be with alcohol fuel?
    Presumably, alcohol has a specific amount of contained energy that can be turned into heat, and this can only be transferred at a certain rate, so regardless of the stove, what would be the fastest possible time you could get water to boil using alcohol (in real world temperatures, atmospheric pressure etc).

    I need a 'bar' to compare the efficiency & speed of different stoves!

    I hope someone knows the answer!
    Thanks!

    Alec

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    Alcohol isnt about speed, and anyone pursuing speed with an alcohol stove is just wasting their time.
    Due to the low heat of combustion, it requires twice the fuel wt of cannisters
    You have to work to make it efficient as possible, limit heat losses, to make it competitive with cannister
    Or theres no point. Particularly with the 0.95 oz BRS3000 cannister stove

    There are reasons for alcohol. Fuel management is one. Finding fuel in gas stations is another. Quiet is one.
    Its not a stretch to say that there is no need for an alcohol stove on the AT anymore today. You can find cannister the whole way. The world has changed.

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    500ml in 4:22 using 23ml of denatured alcohol is the best I've done.

    However, in the scheme of things, using less fuel is FAR more important than speed, so a setup that uses 13ml of fuel and takes 8 minutes is much better.

  4. #4

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    Absolutely - I've used alcohol stoves for years for exactly this reason.
    I can't help but wonder though - there must be a theoretical fastest boil time. It would be interesting to know in order to try and compete with canister stoves...

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    Quote Originally Posted by cmoulder View Post
    500ml in 4:22 using 23ml of denatured alcohol is the best I've done.

    However, in the scheme of things, using less fuel is FAR more important than speed, so a setup that uses 13ml of fuel and takes 8 minutes is much better.
    An engineer would say this is 1 liter per minute, if you use 9 stoves. A scientist would suggest a cookie sheet stove; 53X38 cm for 0.5 cm of water and 66 X 46 cm for the alcohol. I think this would break the one minute/liter mark.
    A theorist would not agree with your assumptions. Nobody agrees with what is real world. You say you have seen a lot of boil times, the fastest one is your target.

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    Quote Originally Posted by feltproductive View Post
    Absolutely - I've used alcohol stoves for years for exactly this reason.
    I can't help but wonder though - there must be a theoretical fastest boil time. It would be interesting to know in order to try and compete with canister stoves...
    The ultimate limit is dependent on heat transfer inside the pot due to natural circulation. It has nothing to do with alcohol or fuel source, per se. This is the controlling coefficient in the heat transfer.

    I can make a big , heavy, wasteful alcohol stove that heats as fast as a cannister. But there is no reason. I can agitate the pot contents to greatly boost the internal coefficient....but why? It weighs more.

    For example, the supercat comes closer, boiling in almost same time with a large wide pot with lots of bottom area to engulf in flame, but takes twice the fuel of most alcohol setups to do .

    Speed is a completely worthless criterion for stoves, unless sharing for multiple people. In which case you should have a jet boil.

    I run my cannister slow....7-8 min boil time. Why? Because it uses 0.18 oz to boil 2 cups doing that. A jetboil is only 0.15., while faster. I can get 22 -2 cup boils on.a small 110 g cannister.

    The most mportant part of an alcohol stove us not the stove at all. Its the windscreen. Its purpose isnt just to shield wind and protect flame from blowout Its to limit excess air to maintain a high flame temp.

    Its the same as comparing a ferrari and porsche top speeds, for buying your work commute car. Wasting your time.
    Last edited by MuddyWaters; 09-21-2017 at 10:15.

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    If you've done much research on alcohol stoves, I suspect that you've seen THIS WEB SITE: Zen and the Art of the Alcohol Stove. But in case you haven't, I'll point it out now. I think they discuss some of these issues.

    I've done a little bit of research on alcohol stoves a few years ago, read this website and a few others. I think it was from Zen that I read things like to get a faster boil (or was it more efficient burn) you had to have a pressurized stove as opposed to a low pressure setup... like the "cat can" stove.

    Don't recall where, but I also recall finding YouTube videos where what appears to be what I would call an Alcohol Stove Building Master was able to build some interesting and relatively complex stoves (compared to the relatively simple Zen designs) that included creating vortex flame patterns and some other designs that seemed to improve the boil time. But when I tried one of the designs, I quickly learned just how much more construction stills these guys had.

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    Quote Originally Posted by ARambler View Post
    An engineer would say this is 1 liter per minute, if you use 9 stoves. A scientist would suggest a cookie sheet stove; 53X38 cm for 0.5 cm of water and 66 X 46 cm for the alcohol. I think this would break the one minute/liter mark.
    A theorist would not agree with your assumptions. Nobody agrees with what is real world. You say you have seen a lot of boil times, the fastest one is your target.
    1) I did say this is the best I've done.

    2) I prefer to deal with practical setups that work on the trail.

  9. #9

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    Thanks for all the insights!
    Yeah I've read a lot of info online, but lots of it is conflicting, opinion based or based on numbers that weren't measured in a controlled environment.
    I hadn't considered the use of a windscreen to encourage flames to burn hotter, and ARambler threw out some interesting thoughts about increasing the surface area of the water to increase the boil time.
    I know that for most UL hikers, it's the efficiency of alcohol stoves that appeals - but there's a reason why people like jetboil advertise how fast they can boil water! I suppose I'm just wondering if an alcohol stove could ever come close to a canister stove boil time. I've heard of some people getting boils between 3-4mins with chimney stoves etc, which is pretty impressive.

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    Quote Originally Posted by HooKooDooKu View Post
    But when I tried one of the designs, I quickly learned just how much more construction stills these guys had.
    I had a similar experience trying to make the vortex stove... 2 of 'em, in fact.

    The Simple Groove Stove is much easier.

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    Quote Originally Posted by feltproductive View Post
    . . . I love Alcohol Stoves. . .
    Does anyone know what the theoretical FASTEST boil time would possibly be . . . I need a 'bar' to compare the efficiency & speed of different stoves!
    As noted above, the theoretical fastest boil time depends on a lot of uncontrolled variables. In the end, you don't really care about the fastest possible boil time with alcohol fuel, you care about the fastest boil time within reasonable constraints of a reasonable weight stove heating a reasonable sized pot that is of reasonably usable design for backcountry use, etc.

    So, if you want a "bar", I would recommend giving up on theory and going with some arbitrary, but relevant standard.

    Pick a standard pot that you might use, many or most people use, or maybe the biggest diameter pot you might use as the standard. Assume indoor conditions so the issue of wind can be eliminated because managing that variable in a standard way across multiple home experimenters would be impossible.

    Then finally, pick any reasonable boiling time for your standard apparatus and use that boiling time as your standard.

    For example: Let's pick some super repeatable variables and run with it:
    1) Imusa 12 cm cup/pot an aluminum foil lid with 2 cups of water at 70 degrees in a nearly windless space like your stove top.
    2) Now, let's pick some standard boil time 5 minutes should work find.
    3) Now we have our bar. Any time we heat water with our experimental stove under the above conditions the performance = 5 minutes divided by test time. If boil time was 4.7 minutes then performance was 1.06. If boil time was 6.2 minutes, then performance was 0.81. So, the bigger the number, the higher the performance, and anything over 1.0 is better than standard, and anything less than 1.0 is slower than standard.

    Now you have a workable test reference system to compare different stoves with.
    We might even go further and suggest that for any given stove, we can test relative pot performance by comparing an experimental pot with the Imusa 12 standard for a given stove. This setup might actually be a pretty fun community project with everyone interested testing their particular gear to these standards.

    If we're going with standards, we also probably want a fuel standard, say 10 g, so that we could compare the amount of fuel burned to a reference standard. So, if I boil my 2 cups of water with my stove setup using 1/2 max flame power on my BRS 3000T stove and burn 7 g of fuel, I could claim 140% efficiency compared to "standard". Or, if I burned 15 g of alcohol to boil my water it would be 67% efficiency compared to standard.
    I'm not lost. I'm exploring.

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    With alcohol, IMVHO the time factor is almost (but not quite!) irrelevant as long as it isn't a stoopid-long amount of time.

    For instance — and taking it to the extreme — if I could boil 2 cups of 60°F using 8ml of fuel and it took 15 minutes, it'd still be worth it for the extraordinarily low fuel consumption. One can always do other camp chores while the water is heating. I used to do that when boiling 3 cups and it took around 11 minutes... got busy with other stuff and almost before I knew it the lid was jumping off the pot.

    Another technical issue when testing alcohol stoves is whether to measure volume (milliliters) or weight (grams), for which you need a pretty good scale, something with at least 0.1g resolution. Grams can be converted to ml by dividing g by 0.798 which is the specific gravity of denatured alcohol (specifically Klean-Strip DA "Marine Fuel".... NOT the "green SLX")

    In any event, IME a possible standard for boiling 2 cups might be around 20ml (16g) because there will likely be a spread of results above and below that number.

  13. #13

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    Great idea nsherry61.

    Ok so with that in mind (and given that I'm from the UK) I'd say what's the best boil time from 20ml fuel to heat 500ml water indoor (from room temp to boiling).

    Out of interest - if you're not fussed by speed - what's your ideal alcohol stove?
    Has it already been made? Or is it the white whale of the AT?!

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    Quote Originally Posted by feltproductive View Post
    jetboil advertise how fast they can boil water! I suppose I'm just wondering if an alcohol stove could ever come close
    JetBoil ain't the fastest game in town.
    Just checkout the stove specifications online at someplace like REI.
    JetBoil Flash Lite = 5m0s
    Snow Peak Giga Power = 4m48s
    MSR WindBurner = 4m30s
    JetBoil Flash = 4m30s
    Snow Peak LiteMax = 4m25s
    MSR Pocket Rocket 2 = 3m30s
    Primus Yellowstone Classic = 3m0s

    NOTE: If you check out boil times on the JetBoil website, you will find quoted boil times half of what is listed above. This is because the boil times listed above is for 1 liter of water. But the standard JetBoil pot is only 0.8 liters in size, so they quote the time it takes to boil 1/2 liter of water.

    But what makes JetBoil so great is the heat exchanger integrated into their pot improves the efficiency of transferring the heat to the pot so that you shouldn't have to use as much fuel compared to using a pot without a heat exchanger.

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    How many bazillion times must this old and tired discussion be repeated?
    In a nutshell:
    Hydrocarbons are for heat.
    Alcohol is for drinking.
    Or, the WhiteBlaze Speak conclusion:
    At approximately 7 days on trail an eff


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    Out of interest - if you're not fussed by speed - what's your ideal alcohol stove?
    Recently on the Grafton Loop Trail I used the semi-MYOG setup (linked in my post above) using the Sterno Inferno pot and Starlyte XL-3 burner. Hard to measure fuel consumption in the field, but suffice to say it was close to the 13ml per 2 cups I was getting in my tests at home.

    Starlyte_XL_size.jpgSterno_02.jpg
    Last edited by cmoulder; 09-21-2017 at 15:14. Reason: typo

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    Quote Originally Posted by Venchka View Post
    How many bazillion times must this old and tired discussion be repeated?
    Each time a new member comes along and asks.

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    Quote Originally Posted by HooKooDooKu View Post
    Each time a new member comes along and asks.
    New members are unaware of the SEARCH feature?
    Too bad.
    Now, Internetus Interrupts truncated my original reply.
    Somewhere around 7 days without resupply an efficient hydrocarbon fueled stove system gains a weight advantage over alcohol.
    7+ days between resupply points is alien to the Whiteblaze Mantra.
    Below freezing certain hydrocarbon based stove systems gain considerable advantage over alcohol based systems.
    Also contrary to the Whiteblaze Mantra.
    There's a whole other world out there folks.
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    Quote Originally Posted by Venchka View Post
    Somewhere around 7 days without resupply an efficient hydrocarbon fueled stove system gains a weight advantage over alcohol.
    Below freezing certain hydrocarbon based stove systems gain considerable advantage over alcohol based systems.
    This varies so widely, its useless to even claim anything.

    I can make break-even for cannister...... 20+ days.
    With heavy innefficient alcohol setups, its as few as 3.

    Methanol is actually a better fuel below freezing than cannister. Cannister only works if you keep it warm and use it minimally so as not to cool, or have a form with heat feedback. Leave it outside all night at 15f...not so useful.
    Last edited by MuddyWaters; 09-21-2017 at 15:15.

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    Did I specify which hydrocarbon fuel was superior below freezing?
    You assume without facts in evidence.
    As for the break even point in the alcohol vs. canister debates, the 7 day case is regurgitated frequently here.
    No worries. Do as you please. All stoves will work somewhere, someway, somehow.
    When in doubt, build a fire of natural fuels found on the ground.
    Later Y'all. I have plans to make for 2018.
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