Alcohol Stove Math
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 Dan Durston (dandydan) - F Locale: IntoCascadia.com FeatherFire vs. PocketRocket on 09/11/2009 20:18:51 MDT My FeatherFire arrived today so I decided to conduct some tests to compare it to my PocketRocket. I wanted to see which is lighter....the Pocket Rocket or the FeatherFire plus windscreen. The FeatherFire (46g) + Windscreen (33g) weighs virtually the same as my Pocket Rocket (87g) so it all comes down to how much fuel they use and the canister weight. Note that I am using methanol in the FeatherFire, which is about 30% heavier than ethanol to accomplish the same thing.I started out by doing 2 tests per stove for boiling a pint of 65F water. I did one test at max power and the other at about 2/3 power. The FeatherFire took 6:30 (max power) and 7:15 (2/3 power) in addition to letting the stove warm up for 30 seconds each time. The fuel usage was 18g and 17.3g respectively.For the Pocket Rocket, the same tests took 2:35 and 2:50 using 6.9g and 5.7g of fuel respectively.Averaging these tests, we can see that the FeatherFire takes about 6:54 and uses about 17.6g of methanol to boil a pint of water, compared to 2:42 and 6.3g for the Pocket Rocket.This means that the FeatherFire uses about 11g more fuel per pint, but it also doesn't have the 135g canister weight to deal with. A 135g canister contains 8oz or 227g of fuel. Using the 6.3g/pint figure, one 8oz canister has the potential to boil about 36 pints of water. Since the PocketRocket saves 11g per pint, after 12 pints it would have saved the weight of it's canister and would then become the lightest option. Not bad...I usually boil 4 pints per day for myself, so the FeatherFire stove would be ahead for weekend trips while the Pocket Rocket would take the lead by day 4. However, I could just bring a 4oz fuel canister with the PR instead of an 8oz one for weekend trips. These 4oz canisters probably weigh about 100g (total guess) and can burn 18 pints, so the Pocket Rocket using one of these would pull even around the 9th pint (100g/11g per pint).Overall, the FeatherFire is only looking advantageous for short trips or trips where I'm not going to boil too much water. However, the FeatherFire has a few other advantages in that it's nice and quiet and the fuel is dirt cheap. It does take longer to boil but that's not a concern for me.I think I could greatly improve these results by making a few chances to the FeatherFire's setup. First, I could add a reflector disc to the FeatherFire which supposedly reduces boil times by about 30 seconds and correspondingly would save about 1.5g of fuel per pint. Secondly, I could switch to using ethanol which is about 30% more effective for the weight. Using methanol I would probably have been using 13-14g per pint instead of 17-18g and coupled with a reflector disc, I could probably achieve pints using around 12g of fuel. If I can realize this, it would drop the weight penalty per pint from 11g all the way down to 5.7g (12g - 6.3g).Under these assumptions, the PocketRocket with an 8oz canister would take 24 Pints (135g / 5.7g) to earn back the weight of it's canister....or twice as long as before. That starts to look pretty appealing for the FeatherFire since rarely do I boil more than 24 pints in one trip. Even camping with my wife, that would take 3-4 days of cooking for the both of us.Comparing a FeatherFire cranking out 12g pints vs. a PR with a 4oz fuel canister and 6.3 of fuel per pint will be interesting. Lets see....if the canister weighs 100g then it would take 18 pints to save enough fuel to cancel that out. However, a 4oz canister can only burn 18 pints if it takes 6.3g per pint so you never come out ahead with one of these. Plus the average weight per day of your trip is higher since the FeatherFire is down to just 1 oz for the fuel bottle by the end of the trip, whereas you always need to lug the canister along with the PR right until the very end.Now if I can just start achieving 12g pints with the FeatherFire.....first I need to get some ethanol. Too bad the darn stuff isn't sold in Canada. I need to smuggle some across the border :) Edited by dandydan on 09/11/2009 20:27:42 MDT.
 Troy Ammons (tammons) - F - MLife Alcohol Stove Math on 09/11/2009 20:52:57 MDT I dont know much about the efficiency of methanol vs DN alcohol. My most efficient MYOG pressure stove would boil 2 cups of h20 with 15ml (11.6 grams) of DN alcohol to a rolling boil in a 24 oz Heineken pot.32 1 pint boils weighs 12.2 oz total with your canister stove.32 1 pint boils as above with DN alcohol would weigh 12.54 oz + 1oz for a container. Really a wash for 32 boils. Anything less and alcohol would beat it. Something to be said for a fast hassle free boil though, no liquid fuel to spill etc.Can you get DN alcohol up there ??I tested 92% isopropol from CVS and it burned hotter and boiled faster, but it is nasty, smokes your pot etc. Edited by tammons on 09/11/2009 21:27:04 MDT.
 Dan Durston (dandydan) - F Locale: IntoCascadia.com Re: Alcohol Stove Math on 09/12/2009 11:12:30 MDT No I can't get DN alcohol. I don't think it's sold in Canada. I might be able to get 191 proof booze but that's quite expensive and I've never seen any at the liquor store. Maybe it's time to start my own distillery in the basement :)The PR is fast and hassle free, although I am really diggin how quiet the alcohol stove is. You can hardly talk over the roar of a Pocket Rocket. I think I'd take the peace and quiet over the faster times of the PR if I can make the weight numbers work.
 Troy Ammons (tammons) - F - MLife 200 proof on 09/12/2009 11:27:09 MDT Corn mash if you want the real deal. I make corn mash to hunt hogs with and its pretty easy once it gets going.All you would need is a lab distiller and a heat source to pull the alcohol off.
 Roger Caffin (rcaffin) - BPL Staff - MLife Locale: Wollemi & Kosciusko NPs, Europe Re: Re: Alcohol Stove Math on 09/12/2009 15:17:55 MDT Hi Dan and TroyPerhaps you might like to read our series on alcohol stove fuel efficiency?http://www.backpackinglight.com/cgi-bin/backpackinglight/alcohol_fuels_part_one.htmlhttp://www.backpackinglight.com/cgi-bin/backpackinglight/alcohol_fuels_part_two.htmlCheers Edited by rcaffin on 09/12/2009 15:18:26 MDT.
 Dan Durston (dandydan) - F Locale: IntoCascadia.com E85 on 09/12/2009 15:41:02 MDT This is probably silly, but what about using E85 or E95 in an alcohol stove? Would the 15% (or 5%) that is gasoline render this fuel dangereous to use? Or would it perform like ethanol?If it is dangerous because of the gasoline, is there a way to remove the gasoline? Perhaps the gasoline is more volatile and thus would evaporate off quickly if you left it un-capped. Environmentally, that's not such a great idea but I'd be interested in knowing if it would work.
 Troy Ammons (tammons) - F - MLife Not safe IMO on 09/12/2009 15:58:41 MDT Might blow yourself up. Gasoline is way too volatile.Can you get 93% isopropol alcohol ?? IT burns hot, but its dirty.
 Roger Caffin (rcaffin) - BPL Staff - MLife Locale: Wollemi & Kosciusko NPs, Europe Re: Not safe IMO on 09/12/2009 19:53:18 MDT > Can you get 93% isopropol alcohol ?? IT burns hot, but its dirty.And the fumes during burning are toxic. Gave co-author Tony Beasley a very bad hangover.Cheers
 Roger Caffin (rcaffin) - BPL Staff - MLife Locale: Wollemi & Kosciusko NPs, Europe Re: E85 on 09/12/2009 19:56:15 MDT > what about using E85 or E95 in an alcohol stoveI doubt that E95 would be very different from some forms of denatured ethanol. E85? Dunno - depend a bit on what's in it. Does it contain benzene (autogas usually does)? Be aware that benzene is a known carcinogen. Other additives?Cheers
 Mike Clelland (mikeclelland) - MLife Locale: The Tetons (via Idaho) Alcohol Stove Math on 09/13/2009 15:04:33 MDT De-natured alcohol math..07 liters of fuel per person per day.
 Lynn Tramper (retropump) - F Locale: The Antipodes of La Coruna Re: FeatherFire vs. PocketRocket on 09/13/2009 15:31:01 MDT What was the starting volume you used for the Featherfire test? It actually makes a difference to the fuel efficiency. Also, did you recover unused alcohol by using the snuffer cap, or just guesstimate the fule neeeded? I find the best fuel efficiency is starting at at least 25ml fuel, then snuffing the flame and recovering the unused portion.There's also another way to increase the fuel efficiency (and speed) of the Featherfire that you can't (as in shouldn't) do with a Pocket Rocket...use a Caldera Cone for the windscreen. This also makes the Featherfire more stable and wind-worthy. Although the pot will sit a little above the top of the cone, it still increases fuel efficiency.
 Dan Durston (dandydan) - F Locale: IntoCascadia.com Re: Re: FeatherFire vs. PocketRocket on 09/13/2009 15:48:40 MDT Just the stove weighs 42g and I weighed the stove + fuel at about 80g, so I had about 40g or nearly 2 ounces of fuel in there (I think a fluid oz of methanol weighs 22g).After the stove was out, I extinguished it with the snuffer and then weighed the stove with the fuel still in it, and the difference was my fuel used. I did recover the unused fuel using the vacuum sucker cap thing that PackaFeather sells.I am going to try to make a caldera cone for this. I'm working an insane amount right now (ie. 54 hours of the last 70) but Tuesday I'll have time to try some stuff. I'll make a Caldera Cone (there's a great YouTube vid).I learned that the highest alcohol they can sell here in BC is 151 proof (75%) which wouldn't be any more weight efficient than methanol. I can get 191 proof alcohol in Alberta but that's a 10 hour drive away. I'm better off to go to the states. Alcohol is really expensive in Canada too. A 20oz of 151 Rum is \$35....not really worth it. I'd love to get some denatured ethanol, but that might have to wait a few months until I visit the USA.
 Dan Durston (dandydan) - F Locale: IntoCascadia.com Gonna be a week on 09/15/2009 22:44:47 MDT The testing is on hold for a bit because I'm waiting for my new 1.3L Evernew Ti pot to arrive. I don't want to spend hours making all sorts of windscreens and a caldera cone for my current pot which likely won't be seeing trail time anymore.
 Dan Durston (dandydan) - F Locale: IntoCascadia.com More Boiling on 09/16/2009 00:32:23 MDT I couldn't resist playing with the FeatherFire...it's such a neat stove. I boiled 2 more pints tonight. I wanted to see how my stove would fare without a windscreen in dead calm weather, so I boiled these pints inside on my kitchen table.The first pint I boiled at about 1/3 power. I didn't measure the time but it took a while....probably 12-13 minutes I'd guess. That used 17.4g of methanol which is the same amount as I used outside with a windscreen, but at 2/3 throttle. That pint outside took about 7.5 minutes. Now I wonder how this stove would do at 1/3 throttle with a windscreen...hmmThe second test was a repeat of the first test but at full throttle. That was way faster but used 20.2g of fuel which is 2.2g more fuel than the same test took with a windscreen.
 Dan Durston (dandydan) - F Locale: IntoCascadia.com More Tests on 09/16/2009 17:59:46 MDT My new Evernew 1.3L Non-Stick Ti pot arrived today so I spent about 3 hours making a caldera cone for it. The results were disappointing.With the new cone, I boiled a pint indoors on my stove top. It took about 8 minutes and guzzled 19.6g of fuel. That's my second worst test yet, with the worst being no windscreen, indoors and the stove on max.I repeated the test using my traditional windscreen instead, and the results were way better. That 2nd pint boiled in a 6 minutes and used 16.6g of fuel.....3g less.Obviously there is a problem with the cone. I suspect the stove isn't getting enough oxygen. Next I'm going to try to improve the breathing of the cone by adding some more ventilation holes to it. I'm not that optimistic though. The cone weighs 75g (2.6oz) and my windscreen weighs 52g (1.9oz). Both are made from roofing flashing.I suspect at the end of this testing the winning combination is going to be an oven liner windscreen weighing about 15g (0.6oz). Even working well, I'm skeptical that the caldera cone can save enough fuel to overcome a 60g (2.1oz) disadvantage in a reasonable amount of time. I think a light oven foil reflector disc (4g or 0.2oz) will also prove valuable and be worth the weight. A FeatherFire, oven liner windscreen and reflector disc should weigh 65g (2.3oz) combined. Compared to my Pocket Rocket (which uses about 7g to boil a pint at full speed), I can start with a 130g headstart because my stove, windscreen, relector is 20g lighter than a pocket rocket and my fuel bottle is 110g lighter than a 8oz canister. This means I would be ahead for about 13 pints if my alcohol stove uses an extra 10g per pint. I think I can reduce this penalty down to about 6g per pint extra fuel by using ethanol and the reflector disc. This means the alcohol stove would be lighter for the first 22 pints (130/6 = 21.7) which is the bulk of trips. Edited by dandydan on 09/16/2009 18:02:42 MDT.
 Dan Durston (dandydan) - F Locale: IntoCascadia.com New Results on 09/19/2009 23:59:23 MDT I made some more modifications to my imitation Caldera Cone. By improving the ventilation, I was able to boil a pint on 17.6g of methanol vs. 19.6g before. That's a nice drop but it's still no better than what I'm doing with a good old windscreen. I boiled 2 pints using my windscreen with an average of 17.1g.I think I'm ready to give up on the cone. I made a new windscreen from an oven liner today that weighs 17g vs. 70g for the cone. I just can't see the cone making back 53g over the course of a normal trip. It would have to perform about 2g better per pint just to break even and right now I can't even get it to match the performance of my windscreen.I boiled a pint just now at 1/2 throttle with my oven liner windscreen (17g) and a reflector plate (2g) at about 60% throttle using 16.1g of methanol. That's a new record!If I could procure some ethanol which is 20-30% more efficient I'd be looking at 11-12g per pint. That's really where I want to be. My fuel bottle is 102g lighter than an empty 8oz canister and my alcohol stove setup is 23g lighter than the Pocket Rocket. That means I have a 125g weight advantage before I consider the weight of fuel. The Pocket Rocket averages about 6.5g/pint which is about 5g less that what I hope to accomplish with ethanol. That means it would take 25 pints (125g / 5g) before the Pocket Rocket breaks even with its superior fuel economy. That's pretty compelling since rarely would I be on a trip longer than 25 pints.Another avenue to explore is how the Pocket Rocket is affected by wind. I suspect the fuel economy would be affected more than my alcohol stove since I don't have a windscreen for the PR. Accordingly, real world conditions may favor the alcohol argument.A second avenue is how effecient these stoves are for larger quantities of water. In my limited testing, the PR took about 80% more fuel to boil 2 pints, whereas the alcohol stove only took about 50% more. I've only a done a few tests so this may be an anomaly, but if this is the case then that strongly favors the alcohol stove when I camp with my wife since we usually boil more than a pint.