When wilderness cooking is concerned, we usually think of either a small stove or a campfire. A backpack stove (powered by Coleman fuel or butane, etc.) is convenient but heavy. Firepit cooking, which is usually supplemented with a grill weighing maybe 6 oz., requires real work to set up and stoke. A few thinkers have blended the benefits of a stove and the weight savings of a campfire — using the fuel available on the ground. Here’s my attempt at developing a backpack stove that blends the two:
Benefits
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- At 18 oz., it’s lighter than petroleum-fuel stoves because you don’t carry any fuel.
- Stove convenience. Faster and far easier to cook on than a firepit.
- Powerful: boils 1 liter of water in 6.3 min. from match touch. Output is 11,000 BTUs/hour.
- Power output is little affected by low temperatures.
- Stable, sturdy, simple, dependable.
- Generous fuel capacity, easy feeding.
- Versatile cooktop. Grill fish over coals, or set various sizes of pots and pans on the stove.
- Compact.
Power output
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Power output of outdoor stoves is usually measured by testing how fast a stove can bring 1 liter of water to a boil under standardized conditions.
Testing under standard conditions shows that this stove will bring 1 liter of water to a boil, starting at lighting, in 6.3 minutes. If considering just the maximum-output portion of the graph, that time shrinks to 3.7 minutes. Stove output is an estimated 11,000 BTUs per hour. Fan output and stove power in this stove are little affected by wind, altitude, or low temperatures. In contrast, cartridge stoves, which run on butane and related mixtures, perform poorly in cool temperatures and tend to become nonfunctional in ambient temperatures somewhere below 32 °F.
Weight savings
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Weights of conventional stoves plus their fuel and fuel containers start high on the first day of a trip and decrease as fuel is used up. The longer the trip, the higher the starting weight. With alcohol, double the fuel weight.
Weight of this wood-fueled stove is a constant 18 ounces: there’s no fuel to carry, no budgeting of fuel, no carrying of excess fuel throughout a trip, no running out of fuel at the end, and no carrying around fuel containers.
Stability
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Naturally, a low-profile, squat stove with a wide base is more stable than a tall one with a narrow base. The height of this DIY stove is a mere 5 inches, while its width is a generous 5¼ inches.
How the stove works
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For fuel, the stove uses natural bits of wood you find at your campsite destinations. Obviously, this is how the stove system eliminates the weight and other problems of artificial chemical fuels. Typical fuel will be twigs, broken sticks, small pine cones, and bits of bark from the ground. At a typical campsite, just by dragging your feet along the ground for 2 minutes, you can create a pile of wood scraps for 2 days of cooking. Loading the stove with 6 oz. of fuel is sufficient to bring a quart or liter of water to a boil in 6.3 minutes.
Sometimes, wilderness deadwood will be moistened by rain. No problem: it will still be burnable and useable. The supercharger of this stove creates a fire that starts dependably and quickly, blasts away as needed, and makes minimal smoke. The supercharger’s fan normally forces a steady 3 cubic feet of air per minute into the fire. Air from the supercharger (and/or passive air from the environment) enters the stove’s preheating chamber, where the flow of air is briefly held, baffled, swirled, and preheated before being forced into the fire. This preheating aids combustion.
This preheating is positioned low where (1) heat is most concentrated and (2) we’d most like it to be for environmental safety reasons. The hot stove embers, or “coals”, are held above the preheating chamber, which serves as insulating air space between the fire and the ground below (which may hold combustible materials on the forest floor). The stove’s combustion chamber is a solid shell in which fuel is tightly managed and heat is focused upward toward the cookware. Wind screening is part of the design.
Construction
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The main stove body is constructed of a rectangle of stainless steel that is folded to create the sides of a hexagonal prism. Its edges are connected using steel rivets. A fuel-feed-port is cut out, and a swinging shutter/door is attached along a horizontally oriented hinge post. The burner bottom starts as a hexagon of the same stainless steel along with a lengthy upward-oriented extension facing the supercharger; triangle cutouts are snipped in at the corners of the shell for air passage, and the burner bottom is attached to the shell with steel rivets. The bottom of the stove is a hexagon of aluminum that is riveted to the shell using aluminum rivets. The grill is cut out of steel grill material and is attached to the shell with two interconnected brass hinges that allow for high and low grill positionings. Details may be gleaned from the photos.
The supercharger shell begins as a complex net composed of aluminum comprising the bottom, sides, front, and rear of the supercharger. Its vertical sides are folded upward from the bottom. Flanges along the various edges are connected using aluminum rivets. A switch is installed in the rear. A 12-volt fan is attached within the front of the supercharger using aluminum rivets. A lid is made to fit the top, and two aluminum rivets in the rear provide a hinging function. A plastic holder for a 9-volt battery is attached to the lid using aluminum rivets. Wiring between the switch, fan, and battery is connected appropriately and soldered. Details may be gleaned from the photos.