Bushwalk Australia

This is a complicated subject, affected by a variety of factors, but complex or no, I give the question my best shot on my blog: Gas Stoves: How Cold Can I Go?

Have a look if you like,

HJ

P.S. Feedback and discussion most appreciated.

Nice theory but in reality I'd suggest finding a liquid feed stove well before -7. They may work down that low (I've never tried quite that low myself) but the performance will be miserable. Personally if it's suppose to be around 0 degrees or less I pack my stove that has a pre-heat mechanism and can run an inverted canister.

sthughes wrote:Nice theory but in reality I'd suggest finding a liquid feed stove well before -7. They may work down that low (I've never tried quite that low myself) but the performance will be miserable.

Well, we may be in disagreement here. Isobutane will vaporize down to -12C, so -7 is a good 5C above that. You should have decent canister pressure so long as the fuel gets no colder.

Now at -12C (the very point of vaporization), I completely agree with you. You'll be eating a cold supper at that temperature.

sthughes wrote:Personally if it's suppose to be around 0 degrees or less I pack my stove that has a pre-heat mechanism and can run an inverted canister.

A good plan, nothing wrong with it, but let me suggest that upright canisters can still be used to good effect as long as the fuel is -7C or warmer.

HJ

hikin_jim wrote:upright canisters can still be used to good effect as long as the fuel is -7C or warmer.

Hey Jim,

If you use an upright canister stove at -7C, does the expansion of gas cool the canister, and if so, how much?

I've noticed that canisters cool as you use then, just wondering if this brings the theoretical low temp limit warmer than you suggest.

Interesting site by the way!

We used the Kovea S/L stoves at -7, no windshield or anything, they were dead slow but did work. Whats happening, wasting gas or just slowing down?? Also found that the windpro aren't exactly choofing along at those sort of temperatures unless the inverted cylinder is placed on top of the boiling pot lid to heat. I have wondered if we are getting diddled on the fuel mix from Kovea?? That powermax fuel would be nice, iirc it is not available here??

photohiker wrote:

hikin_jim wrote:upright canisters can still be used to good effect as long as the fuel is -7C or warmer.

Hey Jim,

If you use an upright canister stove at -7C, does the expansion of gas cool the canister, and if so, how much?

I've noticed that canisters cool as you use then, just wondering if this brings the theoretical low temp limit warmer than you suggest.

Interesting site by the way!

Well, there's a bit of a trick to it: The -7C point is the fuel temperature not the air temperature. You're absolutely right, the canister gets cold as you use it. In order to keep the fuel temperature above -7C, you have to do something to counteract the canister's normal tendency to get cold. Putting the canister into a little plastic tub with (liquid!) water in it will do it if you're using an isobutane blend. If you're using "regular" butane, you're out of luck at that temperature.

HJ

Nuts wrote:We used the Kovea S/L stoves at -7, no windshield or anything, they were dead slow but did work. Whats happening, wasting gas or just slowing down?? Also found that the windpro aren't exactly choofing along at those sort of temperatures unless the inverted cylinder is placed on top of the boiling pot lid to heat. I have wondered if we are getting diddled on the fuel mix from Kovea?? That powermax fuel would be nice, iirc it is not available here??

See my previous post, but the issue is the fuel temperature not the air temperature. The trick is to stabilize the canister temperature above -7 (anything above -7 should be fine). The temperature of liquid water is at least 0C, so putting a canister in a little lightweight plastic tub of water should stabilize the temperature quite nicely.

As to why the Windpro would struggle, I'm not sure. What blend of gas were you using? If you're using the 70/30 iso/pro Kovea blend, you shouldn't have a problem at that temperature, but you want to use the canister upside down from the very beginning, throughout the life of the canister. If you sometimes use the canister right side up, you'll burn off the propane and lose cold weather performance.

HJ

photohiker wrote:If you use an upright canister stove at -7C, does the expansion of gas cool the canister, and if so, how much?

The expansion of gas is actually a relatively small part (about 10%) of why the canister cools. The vast majority is due to the need to vaporize the liquid fuel.

A better way to look at it is that heat is required to vaporize the liquid fuel so that it can be burned (just like with a petrol stove). On warm days this heat comes from the environment for free. When it's cold you need to arrange things differently.

I use an upright canister stove with a windscreen in the winter, no problem at around -10°C.

Nuts wrote: That powermax fuel would be nice, iirc it is not available here??

Powermax, sadly, is no longer available anywhere. Powermax has been discontinued.

HJ

The feedback I've gotten on my blog post is that it's a bit, er, "complicated."

So, how about something really simple? I give you: Practical Cold Weather Gas Tips. Well, hopefully it's practical anyway.

HJ

hikin_jim wrote:

Nuts wrote: but you want to use the canister upside down from the very beginning, throughout the life of the canister. If you sometimes use the canister right side up, you'll burn off the propane and lose cold weather performance.

HJ

Bingo , might need some can stands, should have realised (oh well a bloke cant think of everything at once )

Nuts wrote:

hikin_jim wrote: but you want to use the canister upside down from the very beginning, throughout the life of the canister. If you sometimes use the canister right side up, you'll burn off the propane and lose cold weather performance.

Bingo , might need some can stands, should have realised (oh well a bloke cant think of everything at once )

I don't know what they have at the market in Tasmania, but here a little margarine tub makes a good stand. cut a slot in it for the fuel line and perhaps another for your control valve. It'll hold the canister quite well.

You can also just lean the canister against something.


HJ

I think the original post that I put up may have been a little confusing or at least impractical.

In an effort to remedy that, I've put up a new post on my blog: Canisters, Cold, and Altitude: Gas in a Nutshell.

Basically, I'm trying to tie together several concepts from several previous posts in a (hopefully) practical, step-by-step form.

Have a look and see what you think. Practical? Or still not there yet?

HJ