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Build a Better Windscreen |
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Whether your building a soda can stove, Cat stove, Turbo V8 or Esbit stove, the windscreen is an important part of the stove. Simple changes in the windscreen can drastically effect stove performance. On my Turbo V8 stove I made two screens. #1 was as tall as the pot and had a 1/8" (3 mm) gap around, and #2 barely came to under the handles but had a 1/4" (6 mm) gap all the way around. Normally you would expect the taller and tighter #1 screen to help transfer heat to the pot, but the truth was opposite. I boiled faster and with less fuel using the #2 shorter screen that had better air flow. After much testing I have found that a wind screen should be large enough to have a 1/4" (6mm) gap all the away around. Closer and you choke off the stove, further out and you loose heat. Windscreen height actually matters less than distance to the pot. I found that a windscreen as tall as the bottom of the handles was better than a tall one because it maintained better air flow and weighed less. The best material I have found is aluminum oven liners. I had an MSR stove and the windscreen material they uses is exactly the same. They have this trick of folding the ends over about 1/16" (1.5mm) to prevent cuts and make the windscreen a little stiffer. I haven't found that necessary. You find oven liners in grocery stores and stores like Wal-Mart where they sell disposable aluminum pans used to cook large meats like turkey. If you build a stove to the instructions on this site and still have problems, check the windscreen.
1. Determine the dimensions. Measure for your wind screen height. A good rule of thumb is to make it to the bottom of the pot handles. After determining this height, I add 1/4" (6 mm) to that (optional - see below). To determine the length of the aluminum do the following: a. Find the diameter. The is the entire width of the pot at the widest point. b. Take the diameter and add 1/2" (12 mm) to it. This is the gap for the windscreen around the pot. Multiply this x 3.14, example: pot diameter of 6 7/8" + 1/2" = 7 3/8" (174.6 mm + 12 mm = 186.6 mm). 3.14 x 7 3/8" = 23 1/16" (3.14 x 186.6 mm = 586 mm). Add 1" (25 mm) more for room to bind the ends, and you have 24 1/16" (611 mm). I like to round up to the nearest 1/4" (6 mm), so we make the total length 24 1/4" (616 mm).
2. Cut the screen. Most screens are about 18" - 19" (457 mm - 483 mm) in length in my experience. If your screen length comes out over 18" (457 mm) like in the above example, then add another 1" (25mm) length and cut another piece the required extra length. Example: 24 1/4" - 18" = 6 1/4" (616 mm - 457 mm = 159 mm). 1" + 6 1/4" = 7 1/4" (25 mm + 159 mm = 184 mm) length for the second piece.
3. (Optional). When I tested the MSR Simmerlite Stove, I noticed that MSR uses the same grade aluminum for their windscreens. But those screens stand up well and come back to shape easily after being bent up. The secret is they fold over a little flap of the screen. This is what the extra 1/4" (6 mm) of height is for. At the top and bottom of the screen, bend over a 1/8" (3 mm) wide strip except at the last 1/4" (3 mm) on each end. I find the best way to mark this for an easy bend is to mark it with a marker - the standard one I use is 3/8" (9mm) wide on the narrow.
4. If you decide to not use the fold, you still need to have some extra material on the top and bottom at the ends. Join the ends by making fold over tabs for the ends. These tabs should be 1/2" (12 mm) wide. Join the ends by the tabs and fold one over each way. I once used paper clips, but using this method you can abandon the paper clips.
6. Make a bottom heat reflector from some normal aluminum foil. Do this by placing the windscreen on the foil, then marking the circle on the inside, then cut that circle out. You can fold this up and store it inside the pot and it hardly weighs anything. It also can prevent burning things unintentionally and makes clean up easier some times.
7. To store simply flatten the screen, then fold it in half.
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