Archive for August, 2013

Making a Simple Lightweight Backpacking Alcohol Stove Wind-Heat Screen out of Flashing

Thursday, August 15th, 2013

This article is part of a related series of fuel/stove articles:

One of the keys to efficient boiling/cooking with alcohol stoves is the stove screen/heat shield. There are several components to constructing an efficient stove system, and the most important one is the wind/heat screen.

This screen will work well with Sgt. Rock’s Ion stove or Mark Jurey Penny Stove, or most other types, and should get you close to the maximum efficiency you can get with a flat rolled screen. For other options, see cone type screens and bent in screens (like FlatCat Gear uses). I wanted something a bit simpler than these types of screens however, one that rolls up neatly inside your pot, slots into itself with no weird or unwieldy connector methods.

I have to thank Sgt. Rock, who helped me figure out some of the intricacies of making an efficient stove. His Ion stove / screen / stand system still remains probably the most efficient and simple setup anyone has ever created.

This design is tested fairly extensively and is a little bit different, and more sturdy, than what Sgt Rock has on his site, but the core ideas are the same.

Core Concepts and Goals of Efficient Screens

The ideas behind efficient screens are not that complicated, but some are a bit counter-intuitive.

  • Screen should be quite close fitting, about 1/4″ (6mm) from side of pot gap.
  • Screen should not be too tall. For most pots, 4″ (10cm) is about right.
  • Critical: enough air must enter into burning chamber to allow fuel to not overheat. This is where many screens fail, including most of my earlier attempts, but I did not realize this was the cause. I discovered this by long trial and error, primarily by lifting up fresh, non-holed screens with paper clip legs, then noting that gave me the best efficiency by far of all methods I had tried. Then it was simple math to calculate how many total square inches of air inlet that roughly 1/8″ to 3/16″ (3-4mm) created, then to duplicate that with air holes. The reason you see somewhat jagged airholes on the following completed pictures is that I do not have a punch that creates long air holes, so I formed them by punching out holes, cutting between them with small scissors, then punching a few more pieces off. This creates a few issues with wind, that are however easily resolved.
  • The real key: the screen acts much more like a piston cylinder/carburator than a wind screen. The trick is to get the optimal air/fuel mixture, and to create the best burn chamber possible. This was the hardest point for me to understand, and it took a great deal of testing to confirm what sgt rock had told me via email about this question.

Furthermore, based on some touchy and slightly irksome designs I’d used before, I had the following practical goals for this screen design:

  • Screen should be made out of aluminum flashing, which is easy to get, and very strong, and can be stored inside the pot easily by rolling it up. This material is springy enough to where it generally opens fine to its desired diameter.
  • Screen should have a simple, essentially foolproof method of connecting the two ends. Since I’ve been sewing a lot, a bit of trial and error showed me that a basic flat felled type connection was perfect.
  • Screen should not require awkward storage methods, like most cones do, and should above all be as simple as possible, yet yield the most efficient boils possible, on par with something like the Caldera Cone.

After a decent amount of testing, here is a how to on constructing this screen.
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Fuel Consumption and Pack Weight for Alcohol – Esbit – Canister – White Gas Backpacking Stoves

Thursday, August 1st, 2013

There’s a lot of myths about fuel/stove weight for trip lengths of various days. This page compares consumption weights between several types of setups, over different time frames, using an easy to read table of weights per day/night of the trip, broken into stove / fuel types. As you will see in the table below, basically, an efficient alcohol/esbit stove system will always weigh less at all points of the trip, no matter how many days. This is because the container for canister stove gas weighs about the same as the gas, for 100gm containers, and about 2/3 of the net gas weight for 220 gm canisters.

This article first compared just gas canister to alcohol, but has been expanded to include Esbit and White Gas stove systems.

Of course, all this ignores the sheer silence, clean burning, and beauty of an alcohol stove, plus of course the simplicity, and super light weight of any decent alcohol stove setup, which is the real reason I like these things.

-> Go directly to fuel consumption/carry weight tables.

Basic Fuel Consumption/Pack Weights

See the full tables for fuel consumption/pack weight per day.

Short version, assuming 2 cups boiled two times a day, you will never carry more weight with an efficient alcohol/esbit stove, and you will only carry more weight with a less efficient one on the first day of a 12 day trip. You will basically never make up for the heavier canister container weight, and the heavier stove weight, and you will always never really know how much fuel you truly have left with the canister, whereas with the alcohol, you can very precisely measure out the fuel per boil, knowing exactly what you need to bring and what you can use per day.

Basic testing / efficiency parameters

Alcohol

Alcohol stove comparisons in this chart show two types, one, a very easy to make, fill, and light Ion type stove, and two, a less efficient stove, but faster boiling, like the Penny stove, that requires about 2/3 fluid ounce to boil 2 cups of water. Since a lot of people still use these less efficient alcohol stoves, I thought it would be fair to include that type in the weight comparisons.
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