[pct-l] RE stoves, et al...playing with some numbers...

[Jim Marco]

MendoRider-Hiker,
            Yeah, combustion stuff, had to learn all that crap 40 some odd years ago...No, I would NEVER think of just tossing them.

Numbers? I got so I never did anything without a computer. Note that isobutane is slightly more stable than butane at around 20100BTU/lb. Propane is 21700.
            70/30 isobutane/propane is around 20580 (mixes are never too accurate)
            SLX (50/50 methanol/ethanol) is about  11300
I get about 5/8floz SLX per 2 cups over about 20 tests and averaged. (40F start, in a caldera cone, 12-10 stove)
I get about 1/3floz per quart using WG. (Using a SVEA 123r with 4floz on low with a windscreen, about 12-14quarts per fill, starting at 40F and tested 20 times and averaged.)

My usage:
            Morning: 2 cups of mocha, 2 cups of oatmeal.
            Evening: 3 cups for cooking, 1 cup of cocoa. Another 2 cups of fuel for simmering/baking/frying/etc.
            (Lunches are cold)
About 2.5 quarts per day overall usage. For 2 weeks this is 35quarts (quarts and liters are close to the same.)

Assuming a 2 week outing...about the longest you will ever need on the PCT.
Alcohol:
I need about 3floz of fuel per day for using alcohol. A 14 day supply is a 44floz or a 32floz bottle plus a 12floz bottle of SLX. This weighs about 3oz for packaging (bottles.) The stove/cone weighs about 5oz. (pot, cup and spoon I ignore, they are the same.) I get:
Fuel: 44floz * .8 (density) =  35.2oz + 3oz for bottles + 5oz for stove & cone
Start weight: 43.2oz
Finish weight: 8oz

JetBoil (canisters) (when I tested these, they were 4 and 8oz canisters in the original JetBoil...I am recalculating using 100g and 230g.)

100g canisters are good for 10 quarts. I need 4 for 2 weeks. They weigh about 6.8oz per can: 27.2oz
230g canisters are good for 22 quarts, I need 2 for 2 weeks. They weigh about 12.9oz per can: 25.8oz
Stove weighs about 5.3oz without the cup.

Totals for 2 weeks out:
Start weight (4oz): 27.2oz + 5.3oz = 32.5oz
Finish weight (4oz): 4 cans(at 3.2oz) + 5.3oz = 18.1oz  (plus some extra fuel weight I won't figure.)
Start weight (8oz): 25.8oz + 5.3oz = 31.1oz
Finish weight (8oz): 2 canisters at 4.2oz + 5.3oz = 13.7oz (plus some extra fuel I won't figure.)


For white gas:
WG:
With a 12oz bottle I can get about 34 quarts boiled. (I know, it doesn't quite add up...rounding errors.) But due to field conditions, it will only last about 15 days in the field. (Including priming, wastage, etc...I call it 2 weeks.)
Total weight is 17oz(stove without cup) + 10oz (bottle and fuel together at .8 fuel molecular density) + 2oz screen
Start weight: 29oz
Finish weight: 20oz  (plus a bit of extra fuel I won't figure)


The averages for these:
Alcohol: average:  25.2oz
Canister average (4oz):  25.3oz
Canister average (8oz): 22.7oz
WG average:  24.5oz

Note that for 2 weeks there is no real difference in the averages. Less than 3 oz separates the stove types with 8oz canisters being the lightest and 4oz canisters the heaviest, not a big difference.

I use the least start weight since I assume my food weight will reduce leaving my pack a bit lighter as I go (mostly, the SVEA.)

Every time I do this with different stoves and different setups at my typical usage, the averages always comes out within a couple ounces of each other. Stove types are more user preference than anything else. You really need to look elsewhere (conditions, availability, cost, convenience, volume, etc) to realize any true savings on the PCT, or any long distance trail. Changing stoves will NOT change your pack weight to any significant degree, generally speaking. Use what you have, don't bother changing, is what I recommend. For myself, I like the most reliable, durable stove I can get. About 40 years and the old SVEA has NEVER failed in the field. But, that is just my 2 cents...
                My thoughts only . . .
                                jdm

From: Edward Anderson [mailto:mendoridered at yahoo.com]
Sent: Friday, January 18, 2013 5:05 PM
To: Jim Marco; pct-l at backcountry.net
Subject:

Hi Jim,

That's interesting information. Thanks.  I never knew that propane has about twice as many BTU's/ pound as alcohol. I also didn't know the ratio of fuel weight to the weight of the metal canister. I brought the larger (13 oz.) canisters and assume that the ratio of propane to metal would be higher for the fuel. The reason that I could cook two meals per day for a week was that I usually turned the valve down to less than full flame - that way there was less heat loss outside the utensil. I could turn the valve even lower to simmer. I sometimes also brought the smaller 7 oz. canister and rarely needed to use it - I still have the original, and it's still about half full after six months (four seasons) on the PCT.

I should point out that the proper way to dispose of a canister is to completely drain it of propane. This can be accomplished by turning on the valve and not lighting it. Then you must carry the empty canister out.

MendoRider-Hiker