Isobutane Fuel Canister Estimator

[Jon Fong / Flat Cat Gear]

I am experimenting with a way to estimate the number of fuel canisters that would be needed for a trip.  Yes, there are a lot of factors involved, but this is my first attempt.  The estimator will only be accurate for specific cooking systems; the one that I have chosen is the TOAKS 550 pot coupled with the BRS 3000t stove with an Ocelot Mini windscreen.  The chart is derived from accumulated test data bringing 500 ml of 68 F water up to a full boil in calm and 8-mph winds.  This chart can be expanded to other cooking systems, I just happen to have a complete set of data for this one.

Yes, your water temperatures and volume may be different, but that can be accounted for later.  What I am interested in understanding is the following:

Does the chart make sense?

Does it seem useful?

What improvements need to be made?

 

Jon

[Roger Caffin]

That seems to me to be serious over-complex. Sorry, but.

My method is much simpler: 30 grams per day for the two of us in 3-season, 60 gram/day in the snow. The latter is usually overkill IF I can find flowing water. (Which is not uncommon in Australia.)

For a day walk with morning coffee for the 2 of us: 10 grams.

Sure, I may allow a little extra just in case. I do this by not trying to partly empty the gas canister to minimise weight. A silly exercise imho.

This has worked just fine for the last 20+ years.

Cheers
PS: I ALWAYS use a good windscreen!

[David D]

My custom trip planning spreadsheet knocks this out semi-auto.

Each meal has an entry for # cups boiled water, that gets auto summed for the trip and auto linked to the fuel estimator sheet that auto spits out how much fuels is needed, with 2 options: one for shoulder season (colder water) one for 3 season.

Its been consistently pretty bang on and I trust it.  I use to sometimes change recipes or cut # teas, to ensure a 4oz can will cover the trip

[Jerry Adams]

im a curmudgeon (like Roger?) and just use 1 ounce per day.  And an extra 1 ounce.

I always use windscreen so don’t consume much higher amounts if it’s windy

[Jon Fong / Flat Cat Gear]

It is interesting to see what people do about fuel estimations.  This feedback is really interesting to me.

The Ocelot series of windscreens provide a partially enclosed windscreen for canister topped stoves.  I have found that when using a traditional mug that fuel consumption in high winds nearly double the consumption rate.  With the BRS 3000 stove, this goes from about 7 g to boil 2 cups up to 14 grams @ 8-mph.  The question is, how do you compensate for windy conditions?

The chart was created to look at tipping point: when do I need to bring an addition fuel canister?  The difference being the additional 7.2 oz of weight of a new 4 oz fuel canister (or more).

[David D]

1 oz/day + 1 oz buffer would only good for a 3 day weekend trip.

I use my fuel estimator to safely only need 4oz fuel for up to 8 day trips with low stress, even with hot tea at breakfast and usually again at dinner.  Its painless once set up.

But I keep my fuel needs down by:

• windscreen
• use the Stash pot for up to 40% reduction in fuel consumption vs a toaks.  Its also a lot faster so wastes less fuel in high winds
• cold and (frankly delicious) calorie dense breakfasts of Quaker Harvest Crunch, Nido & dried fruit
• cold lunches (wraps, cold soaks).  I can’t bring myself to purposely cold soak dinners.  I don’t hate myself that much
• custom made hot soaked dinners, no in-pot cooking.  I don’t touch the off the shelf dinners and instead make what tastes great to me and has the right macros

If encountering some unexpected high winds, I conserve fuel by heating to 165F and cutting a hot drink at dinner for some of the following nights.  The hot drinks are a built in emergency buffer

If my trip is a long one, I try to bring a couple dinners that could be cold soaked if for some reason fuel use went sideways.

[Roger Caffin]

With the BRS 3000 stove, this goes from about 7 g to boil 2 cups up to 14 grams @ 8-mph.
Always happens in wind with many upright stoves. That’s an extra 7 g of fuel in windy conditions for every day. On the other hand, my Ti foil windscreen weighs just 7 g, and last for many trips.
That said, I admit I often use my aluminium foil windscreen: slightly heavier as it is higher – higher than needed, really. But I have a lot of aluminium foil.

OK, OK, I keep on about using a windscreen. I know.

Cheers

[Jon Fong / Flat Cat Gear]

David,

Slightly different comparison as you are using a HX mug and not a traditional mug. That being said, here is a Chart of Boils per Canister comparing a couple of cooking systems. The left most system is the TOAKS/BRS/Ocelot system. As you can see, in fair weather, you’re going to get about 15 full boils out of it. Like you said, HX pots have better fuel efficiency so the Fire Maple Petrel/Polaris/Ocelot system can get 20 full boils. In both cases, these system should be fine for most weekend trips. Even in high winds, the TOAKS/BRS/Ocelot system will give 7 full boils. The differences between the two systems really become apparent on trips longer (or more boils) than 3 days where additional fuel will be required.

[David D]

John,

Nice data!  The 8 mph penalty with ocelot is less than expected, nice job 👍

A common perspective is that hx pots don’t justify the weight even on long trips but with that, a wind shielded stove like the windmaster or PRD and an UL windscreen, I think it’s a better trade off for fuel margin (faster boils, better wind resilience) than just carrying more fuel

 

[Jon Fong / Flat Cat Gear]

David,

I am working on a video about that particular topic “When do HX mugs make sense to pack”. In calm conditions, HX mugs do not really make sense. They may in the future, but several things must change. HX can be better at wind robustness and with a windscreen can look quite attractive. In the here and now here is some data on the Petrel G3 with a FM Polaris stove and Ocelot Windscreen. In windy conditions and multiple boils, the difference really stands out. My 2 cents.

[Author]

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