10/12/2015: Stoves

Now that I've decided on bringing a stove (as opposed to going stoveless), the only decision left is which stove system to use. Only 2 options remain at this point: A denatured alcohol Fancy Feast stove and canister fuel with a screw-on stove.

A Fancy Feast stove is a simple, lightweight, and inexpensive option for lightweight backpacking. It is an empty cat food can with holes punched around the top of the can. One simply fills the stove with denatured alcohol (Heet gasoline additive is usually easy to find) and lights it on fire. Once the cook pot is on top, the flames are forced out of the holes creating fairly efficient flames. Normally, this type of system is the lightest for shorter trips. The stove weighs just 6 g and the amount of fuel brought on the trip is adjustable (as opposed to a canister fuel container). In addition, there is flexibility in the alcohol fuel container. Typically, a small 8 fl oz flask (0.95 oz) is just the right amount for a weekend trip. The downsides to this system are its controllability and weight (ironically). Once the stove is lit, the flame is nearly invisible (especially in bright conditions) and will persist until the fuel is spent. In a dry environment where a human-caused forest fire is a real danger, this type of stove is an irresponsible choice since there is no way to shut off the flame. In addition, while this system tends to be lighter for short trips, the relatively low energy density of the fuel becomes the limiting factor for extended trips. Larger (heavier) fuel containers must be carried, and the weight of the fuel begins to offset the savings presented by the stove itself. Below are the stats for this system.

Stove Wt: 0.78 oz (incl stove and windscreen)
Fuel Container Wt: 1.1 oz (16 fl oz Smart water bottle)
Fuel Container Capacity: 16 fl oz
Fuel per Meal: 1.8 fl oz

A "jet stove" and pressurized fuel canister is likely the most common backpacking cooking system. It is safer and easier to use than an alcohol stove system, and is generally lightweight. Because the fuel and fuel container are relatively heavy, it is often overshadowed by an alcohol-based cooking system for shorter weekend trips. However, once the trip length creeps upwards of 5 days, the energy density of the pressurized fuel begins to offset the weight of its container and it becomes the lighter choice. The other benefit of a jet stove system is the ability to positively shut off the flame and fuel source. Below are the stats for this system.

Stove Wt: 3.5 oz (incl. stove and bag)
Fuel Container Wt: 4.2 oz (110g pressurized canister)
Fuel Container Capacity: 3.9 oz
Fuel per Meal: 0.32 oz

The static factors when comparing weights of cooking systems are the stove (plus accessories like carrying bag, windscreen, etc.) and the fuel container (not the fuel itself). One can think of these as "overhead." They must be carried regardless of the trip length. The dynamic factor is the amount of fuel carried, which depends on the trip length. The alcohol-based system has the benefit of flexibility in the amount of fuel carried. On a one night trip, you may only use 15% of the fuel in a jet stove container. However, you still must carry the entire 4.2 oz of the canister because the fuel is pressurized and cannot be repacked into smaller containers. On the same trip, using an alcohol stove, I would only need to carry 1.8 fl oz of fuel, meaning I could downsize my fuel container to something that only weighs 0.7 oz. The comparison table for this trip is below.

As you can see, the fuel container for the alcohol system is able to be scaled down to fit the length of the trip. In contrast, the jet system requires you to carry the excess capacity. In this case, the alcohol system weighs less than half of the jet system.

Also evident in the table are the various other factors which influence the overall weight of the cooking system. Starting from the top, The static weights (stove and fuel container) are listed. Following that, the total and daily mileage of the trip is listed. From this, the total trip length (in days) is calculated. The next input is meals/day. This is anywhere from 0.5 (cooked dinner every other night) to 3.0 (cooked breakfast, lunch, and dinner every day). Total number of meals for the trip is then acquired. The final input is the amount of fuel required per meal. From this, we can calculate the total amount of fuel and therefore the number/size of fuel container(s) needed. The total weight is then simply STOVE + FUEL CONTAINER(S) + FUEL. 

In the next example, the longest resupply stint I will face on the trail (105 miles) is modeled. On the alcohol side, you will notice the changes include: alcohol fuel container weight (changed from small 2 oz bottle to a 16 oz water bottle), miles, and meals/day (assumed cooked breakfasts every other day). This table paints clear picture of the downsides of an alcohol-based system. The fuel simply contains much less energy per oz than the pressurized canister.

From this data, we can plot a chart of the overall cook system weight (vertical axis) as a function of trip duration (horizontal axis). This applies the same parameters (miles/day, meals per day, etc.) to both the jet and alcohol systems while varying the trip length. The point at which the 2 lines cross is the trip distance where the 2 systems would weigh the same. Any shorter and the alcohol system is lighter. Any further and the jet system is lighter. Also of note are the steep jumps that occur at mile 120 for the alcohol system and mile 160 for the jet system. These are the points at which an extra (or larger) fuel container would need to be carried.