2:21 p.m. on November 28, 2011 (EST)
Jim,
Two comments -
In your "Why blended gas..." blog, the blue typeface on black background is almost impossible to read on my iPad, and difficult even on my 17" monitor. Black backgrounds with white type are bad enough, and have been abandoned on most commercial websites. So I would suggest you go to a more "book-like" dark type on a light background. Yeah, I use white, yellow, and other light type in my Powerpoint presentations in classes - and I get complaints all the time about how hard they are to read.
More relevant - there are plenty of ways to overcome the cold weather problem with butane, which have been discussed many times on Trailspace and its predecessors BCU and RCU. One is to use a handwarmer (the powder in a bag type, not the flame type) in the dished-in side of the canister. Primus for years made a "cold weather kit" that did basically that. I haven't seen the kit in a while, so I don't know if they make it. Regular handwarmers work well up to about 15,000 0r 16,000 ft. Higher than that, the handwarmers (and footwarmers) don't get enough oxygen to heat up enough (they work on using the oxygen in the air to oxidize an iron-carbon powder mixture).
A second approach that is also safe is to use liquid water. Set the stove in a shallow pan of water, up to lukewarm. Hotter tends to pressurize the canister too much resulting in flaring. The problem is getting the liquid water in the first place in subzero conditions. But if you are using your waterbottle as an overnight sleeping bag hot water heater, you only need a small amount. Jetboil intentionally designed their group cooking protective cover for the bottom of the heat exchanger pan so you could do this. I have used the "frying pan" lids of various cook kits to do this, long before Jetboil, but since these are metal (stainless, aluminum, titanium, depending on the cook kit), they tend to cool the water too quickly.
Another approach that a long-time contributor, Jim S, experimented with alot was to wrap a copper wire or strap around the canister, with the one end of it in the flame. This acts as a heat pipe to conduct a small amount of heat to the canister to keep it pressurized. You have to watch this carefully, though.
The vaunted "take the canister to bed with you" is very inefficient. It really only serves to get the stove started when it is really cold, though it can allow you to melt enough water to fill the pan.
The inverted canister, which was discovered by a group of us some 25 or more years ago with flexible hose canister stoves, inspired by the PowerMax and a couple other liquid-feed butane and propane stoves and eventually adopted by first Coleman and Primus, then a few years later by Jetboil in their Helios is the best approach. As you note, for this to work properly, the stove needs to have a generator tube (a generator tube is simply having the fuel line run through or close to the burner). This is used on all (or almost all) white gas and kerosene stoves (including the venerable Svea 123, where it is the stem of the burner, rather than a fuel line through the burner). So it works well on the Primus MFS and its descendents, though it does work on some non-generator setups, depending of the hole diameter of the jet.
Another thing to note - at extreme altitudes (6000 meters and up) plain old butane works reasonably well by itself. The old Camping Gaz (now part of Coleman) stoves were used for years on Everest, for example. I have also seen them used at 5000 meters on Denali, though the vast majority of climbers there use white gas stoves.
more»
