Bushwalk Australia

Hi Guys,
So how long do you normally get out of a 300g (I think thats what they are ) gas cannister? Say I was cooking for 2- maybe porrigde for breaky plus cup of tea & say pasta and sauce for dinner & a couple of cups of tea. How long would you guess a cannister would last. Obviously a few variables but a rough idea would be great.
Cheers
Lizzy

A rough rule of thumb is 15-20g of fuel to bring 1 liter of water to boil under benign conditions.

Not sure about your menu but it sounds like you might need to use about 40-50g of fuel, just a guess. Those 300g canisters (more like 360g) have 220g or 230g of fuel in them, so that's probably 4-5 days worth.

thanks Orion... sounds like 1 should be plenty for 3-4 days then

On a recent trip I got 8 days out of one 227g cannister (really only 6 days cooking though) but I have scraped out 7 before. I had my fuel stove break on a 4 day trip to Mt Thetis and we had 3 of us using the one stove for hot brekkies and dinner. We ended up using the last night to cook anything we could to empty the cannister, it took us a while. So like Orion has said, expect at least 4-5 days out of one.

I get 7 days for one person on a 227g cannister (around 3-4 boils per day). Obviously wind can play havoc with the efficiency. On windy trips where full protection of the stove is tricky I may lose a day or two or boils.

Check out:
http://www.bushwalking.org.au/FAQ/FAQ_Efficiency.htm

Where can I buy gas canisters, do any of the big stores carry them, I think I saw some At Big W, just have not been able to drop in an check.


Cheers.

LAMEA-Gals wrote:I get 7 days for one person on a 227g cannister (around 3-4 boils per day). Obviously wind can play havoc with the efficiency. On windy trips where full protection of the stove is tricky I may lose a day or two or boils.

Yes, I found that 227g will last 7 days if you're not wasteful of gas (eg turning the gas right down once the cooking gets under way) and quite easy if you have cold breakfast. It's very hard to judge how much gas is left though and I've previously rationed in the final days of a trip only to eventually find that I was a bit too cautious. The wind does effect gas usage. On a recent Tassie trip, I was frugal with gas usage but one of my companions got at least an extra day's use (2 hot drinks and dinner and possible a bit more) than me by using a home made wind shield. It was made from an aluminium foil baking tray I think and he took care that it didn't exclude air or get excessive heat trapped next to the gas container. It's an example I intend to copy.

Who in Australia reduced the contents of my 230g net canisters to 227g and who knicked my 3 g
corvus

a lot depends on the quality of the gas stove. The less heat escapes into atmosphere the less fuel you'd need to heat the same volume of water and hence the longer it lasts. Mine is a tiny titanium stove that makes this noise like a rocket and it boils 1L of water in about 3 min. I've used one small canister (230g) during last 6 months or so (I think we did about 10 day trips using it twice a day each time

igor wrote:a lot depends on the quality of the gas stove. The less heat escapes into atmosphere the less fuel you'd need to heat the same volume of water and hence the longer it lasts. Mine is a tiny titanium stove that makes this noise like a rocket and it boils 1L of water in about 3 min. I've used one small canister (230g) during last 6 months or so (I think we did about 10 day trips using it twice a day each time

This is true except that it pertains not just to the stove but to the entire cooking system: stove, pot, windscreen, insulation. This is the idea behind the Jetboil with its heat transfer "fins", carefully tuned stove, and insulated pot.

The fuel in a 230 gram canister has a total heat content of about 10.6 MJ. That is enough heat to raise just under 30 liters of water from 15°C to 100°C if ALL the heat goes into the water (100% efficiency). It isn't difficult to get an efficiency of about 50% where half of the heat goes to heating your water and the other half is lost to the environment. In that case you'd expect just under 15 liters boiled.

You didn't say how much water you guys used or what temperature it was at. But ten days, two people, twice per day, and assuming 500ml per use would mean 20 liters of water total and an efficiency of about 67%. That would be quite good. I have managed to get 60% at home without doing anything special, but in the field it is less. Jetboil claims an efficiency of 80% in the lab but with water starting at 27°C. If they used 15°C water their lab efficiency would drop to about 69%.

Of course what people really do is figure it out based on past experience, the amount and type of cooking planned, and the expected environment. When I camp in the winter and have to melt snow I use nearly one 220g canister PER DAY for two people.

Primus Power gas 4 season Mix, has anyone used this gas, I just bought one and was wondering what makes it 4 seasons, is it the same as other gas, just says 4 season, I was thinking it has something special in it to make it work better in winter at least ???

I looked on the can, but can't see any info, not even the Propane and butane mix percentage is stated.

It does say it has Propane, IsoButane and Butane, what is isobutane, thought it was isobutane butane all the same stuff, but maybe isobutane is a separate ingredient ?



Cheers.

Orion wrote: Jetboil claims an efficiency of 80% in the lab but with water starting at 27°C. If they used 15°C water their lab efficiency would drop to about 69%.

They have to be kidding, 27 Celsius Try sub tens in Tassie. Marketing, just has to make you wonder O'well I will see how I go with my new light weight version of the Jetboil, the 800ml one.

On a very unscientific usage I would say at the moment the Primus ETA system is the best gas system that I have as it has a very effective heat shield system. Not so sure on the the bigger Jetboil system that you invert the canister. It looks horribly like the ETA burner and I did not find it all that brilliant. Not bad, just not up to the over hyped stage.

Gas usage is a tricky thing to predict as stove, conditions and most importantly the person an what they cook play a major role.

Cheers

Orion wrote:Jetboil claims an efficiency of 80% in the lab but with water starting at 27°C. If they used 15°C water their lab efficiency would drop to about 69%.

This is wrong, I don't know what I was thinking. They claim 80% lab efficiency and use water that is 80°F (27°C), but changing the water temperature doesn't alter the efficiency as I mistakenly calculated.

What does change with the starting water temperature is the number of liters they claim you can boil with one canister. Most of the time a lower temperature is used as the benchmark lab value, for comparison purposes. That they use a higher temperature is a little slippery marketing-wise.

John Sheridan wrote:Primus Power gas 4 season Mix, has anyone used this gas, I just bought one and was wondering what makes it 4 seasons, is it the same as other gas, just says 4 season, I was thinking it has something special in it to make it work better in winter at least ???

I looked on the can, but can't see any info, not even the Propane and butane mix percentage is stated.

It does say it has Propane, IsoButane and Butane, what is isobutane, thought it was isobutane butane all the same stuff, but maybe isobutane is a separate ingredient ?

John, isobutane is an isomer of butane. That is, they have the same chemical formula but the molecules are "shaped" differently and this affects their properties. Specifically, isobutane is more volatile than butane: at any temperature its vapor pressure is higher than that of regular butane.

When you use a canister the more volatile components are exhausted at a faster rate so that by the time you are getting to the end it is almost as if you never had any. Going from full to empty, the gas pressure slowly drops to that of the LEAST volatile fuel component. So it is better to have a mixture that has isobutane rather than butane as the least volatile ingredient because the pressure will be better near the end, and this means it will be easier to use in the cold.

The Primus gas has quite a lot of regular butane in it, the "Four Season" label notwithstanding.

See this: http://bushwalk.com/forum/viewtopic.php?f=15&t=7683#p105631

OH great I bought the second worst gas, there go's my trip to Antarctica

I guess I will have to settle for Australia and somewhere hot in summer, any ideas

Cheers.

John Sheridan wrote:I guess I will have to settle for Australia and somewhere hot in summer, any ideas

Simpson Desert sounds good.

Speaking of which , hot /warm conditions will cheap Butane work as well the expensive mixed ones in those conditions ?
corvus

corvus wrote:Speaking of which , hot /warm conditions will cheap Butane work as well the expensive mixed ones in those conditions ?

Pure butane fuel works perfectly in warm conditions. You can even use it in the cold but it is more difficult to keep warm enough. That's all.