As Will Rietveld shows in his two articles on windshields Part 1 and Part 2, running a stove without a windshield can be, at best, a good way of using a lot of fuel, and at worst a total exercise in frustration. But finding a suitable windshield for your stove can be difficult. Most commercial butane/propane and liquid fuel stoves do come with an aluminium foil windshield, but these ones are usually fairly heavy. For instance, a couple I have here are made with 0.23 mm (0.0092") soft aluminium foil, and a 6" high unit weighs 76 gram (2.68 ounce). They are just a strip of foil with a large roll-over at the edges (5 - 7 mm or about 1/4") and a couple of corners cut off to let the fuel hose pass through. One could wish for something better and lighter.
An obvious alternative is to make your own windshield, but this is not so easy. Finding suitable aluminium foil at your local hardware store seems difficult or impossible: mostly the stuff they stock is far too heavy. The aluminium dampcourse I can buy in Australia is 0.27 mm (0.0106") thick: even heavier. You can use foil from a disposable baking dish, but usually the dish is too short. You can use cooking foil, folded several times, but this is really only suitable for small windshields under about 3" in height. Will has suggestions for other designs, but they may not be what you want either.
The Trail Designs windshields are made from aluminium foil only 0.14 mm (0.0055") thick. They come in three nominal heights: 4", 6" and 8", although actual heights are 112 mm (4.41"), 162 mm (6.38") and 200 mm (7.87"). The length is about 710 mm (28"). This is enough to make a complete wrap-around windshield of just over about 210 mm (8.5") diameter, which is distinctly larger than most 2-man cooking pots. For instance, the AntiGravityGear 2 quart pot is somewhat less than 150 mm (6") diameter, while the 1 quart GSI Bugaboo pot [link to this] is right on 150 mm (6") diameter. This means the Trail Designs windshield in complete wrap-around mode would have a gap between the Bugaboo pot and the windshield of about 30 mm (1.2"), which is probably slightly more than you need. Yes, the edges are rolled over for strength and safety, but only by about 1 - 2 mm (about 1/16").
Even so, this is hardly something to get very excited about. It's just a strip of aluminium foil, after all! But Trail Designs have a patent-pending feature which convinced me that the Vari-Vent units are a step forwards. Before I explain what this is, let's look at what normally happens when you unroll your foil windshield and try to put it around your stove and pot. You get it just right, and sproing! It rolls up or springs away or generally misbehaves. This is bad enough, but if there is some wind around the behaviour of the very light bit of foil becomes even more unpredictable. This is a pain. Various solutions involving tent pegs have been promoted, but they don't seem to have caught on, and are hard to use when your stove is on sheet rock anyhow. I have tried other light materials, but the corners kept getting in the flame and burning ... and my wife complained about the smell. The problem seems to be that the ends of the windshield are free to go anywhere they want.
The Trail Designs variable vent, opening outwards
There is a simple solution to this wayward behaviour which works anywhere, and weighs nothing: join the ends together firmly so the windshield sits in a stable solid ring. Anyone who has tried this will agree that it works, but with ordinary windshields it leaves the stove without an air inlet. This is not good, and can lead to poor performance and carbon monoxide production (I have been able to measure the latter). You can punch holes around the bottom edge of the windscreen (as found in some other commercial windshields), but different conditions seem to need different numbers of holes in different positions, which can be awkward in practice. You can raise the windshield up on a few stones, but this seems to be a bit unstable at times and very hard to adjust. We need a better way to control the air getting in which is stable and does not add weight.
Enter the Trail Designs solution. They have punched three-sided holes right around the bottom edge of their aluminium foil Vari-Vent windscreen. This is best explained by referring you to the picture to the left. The flap can be adjusted to do anything from completely closed to block off the wind to wide open to allow lots of air supply. This is terribly simple, and you can adjust this so easily in the field. You can close off the flaps on the windward side and leave open the ones elsewhere, and you can adjust the airflow as much as you wish. The instruction leaflet suggests you don't do this while the stove is running, but it is easy enough if you are careful. Have the flaps poking outwards, and then a small stick can be used to adjust them. It's best to hold the top of the windshield down while you do this, preferably with another stick as the air and the metal there may be a little hot! Just don't get burnt. Now you have a completely adjustable but stable windshield.
The folded join from above
How do you join the ends together to make this into a stable ring? You can use various sorts of paper clips of course, but these are never entirely satisfactory in my experience. I find that folding the two ends back by about 1/4", one inwards and the other outwards, gives me a join which is really secure and quite simple to connect in the field. This is illustrated to the right. I hook them together and give them a bit of a squeeze. Note that I haven't creased the fold down hard: you shouldn't do this as you need to leave some room inside the fold for the other end to fit. On the other hand, you do need to crease it a little to stop it from falling apart when you shuffle the pot and the stove around in the field. Fortunately, the hook joint resists a lot of my clumsiness. (You can of course do this with other brands of windshields too.)
Which height do you need? Many alcohol stoves are only about 50 mm (2") high with whatever pot stand they are using, so the 4" windshield is be ideal for these. Granted, cooking foil is even lighter, but I have found that cooking foil disintegrates over time, and on a long trip this can be a pain. Equally, the extremely light and flimsy cooking foil windshields are much harder to control, while the complete circle of one of these is far more stable.
The 6" units may be useful with some remote tank liquid fuel stoves, especially the ones 4 inches high or more. The 6" windshield should give a couple of inches cover over the side of the pot. You need to make some arrangement to pass the fuel line through the ring - it is often easy enough to to use one of the existing vent holes for this. This will depend a bit on the stove and a 'comfortable' height for the fuel line. In the picture below the red arrow shows the fuel line going through one of the vents. You could also use an 8" unit with such a stove if you expect to have to handle really high winds, but I doubt this would be really needed. Since liquid fuel stoves usually have the control valve on the fuel tank, which is outside the windscreen, adjustment is easy.
I have found the 8" unit really convenient with an upright canister stove. The pot rests on such a stove are usually about 150 mm (6 in) above the ground, so once again the windshield will cover a couple of inches of the side of the pot. A higher windshield might protect the pot even more from cooling winds, but it would weigh more and I don't think it is necessary.
Field use of an 8" Vari-Vent windscreen with a Coleman Ti Fyrestorm stove - the windscreen is higher than needed.
What length do you need? Well, Trail Designs supply the Vari-Vent windshield in a single fairly long length of 28 inches, but a couple of inches at each end is clear of holes. You can chop short bits off each end and still have room for the hook joint, to make it have exactly the clearance you want on your favorite cooking pot. If you are using a smaller one-man cooking pot you may want to chop off a bit more than the little bit at the ends. In this case you can chop a longer length off one end by including a hole (or two). Just rememebr to leave about 1/2 inch for the hook joint.
Of course, once you wrap one of these windshields right around an upright gas stove you can't access the control handle. This also applies to the new Coleman Fyrestorm Ti remote-canister stove, where the control valve is at the stove. I solved this problem very easily by cutting a neat small hole in the windshield just where the control handle on my upright stove would be. The picture here shows this hole with a blue arrow. This was still a little awkward with my SnowPeak GST-100 stove as the handle was quite short, so I made a slightly longer handle with some Ti wire from the Backpacking Light store. Since the original handle was steel, the new and longer handle was actually lighter. The hole I made is rather small: it might be better to make a slightly larger hole to access the control - the stove will need air after all.
The windshield in this picture is actually much higher than I needed. I was using it because I was also testing out the new Coleman Fyrestorm Ti stove at the time. The control handle for it has fitted through one of the vent holes, marked by the green arrow. Of course, one or two extra small hole hardly makes any difference.
Can an ultra-lightweight walker justify carrying such a windshield? If what you have is a very small low alcohol stove, maybe not. In that case some cooking foil, renewed every few trips, may be enough. But if the stove you are using is slightly higher the cooking foil idea doesn't work that well, and the weight of one of these windshields can be justified. How so? Well, look again at some of the results from Will's research. When a stove has to struggle in a wind to bring water to the boil, it uses more fuel - in some cases lots more fuel. Will writes "In my alcohol stove tests, I found a 38-320 percent increase in fuel consumption to boil one pint of water in a 12 mph wind, and that was WITH a windscreen." That fuel has weight. My own experiments over the years suggested that I had halved the weight of fuel carried by using a windshield and a lid. Over just a few days the extra fuel required to run a bare stove in the wind can easily be more than the weight of one of these windshields. A smart walker carries and uses a windshield - with any stove.
What is the best way of packing one of these away? Commercial units (Trail Designs and others) seem to come folded up, but repeated folding will damage the foil, sooner or later. I prefer to smooth the foil out carefully as soon as I get it, and then to roll it around one of my water bottles and secure it there with a rubber band. If I lose the rubber band, it doesn't matter.
Could the windshield be improved? Of course it could: it could be made out of even thinner (lighter) aluminium foil - but then it would have to be a harder alloy and we come back to the problems of availability. Or maybe it could be made from a different metal: hard stainless steel shim, or even titanium foil. However, you can be sure that these more exotic metals would make the windshields far more expensive!
Is the windshield perfect? Nothing ever is. The one problem I haven't solved really well so far is how to light my stove inside such a circular windshield. When the windshield only covers three sides out of four I can come in on the fourth side with my butane lighter. But when the windshield covers a full circle I have to come in from above - and that risks scorching the hairs on the back of my hand. I have found two solutions for this so far. The first involves lifting the windshield up and out of the way while I light the stove. Fine, except in serious winds. The other is to erect the windshield as a 3/4 circle, light it, then join the ends up. This latter is more fiddly, and I have to watch out for the flames while making the join, but it does work reliably.
Trail Designs display these windshields on their web site www.traildesigns.com, but marketing is currently done through the Anti Gravity Gear web site www.antigravitygear.com, where they are listed under Stoves.
Features and Specifications
|4"||112 mm (4.41")||32 g (1.13 oz)||US$7.95|
|6"||162 mm (6.38")||44 g (1.55 oz)||US$9.95|
|8"||200 mm (7.87")||54 g (1.90 oz)||US$11.95|
- Typical length: 28", enough for a diameter of 8.5"
- Foil thickness: 0.14 mm (0.0055")
- Can be trimmed to length required
- Can be joined into secure circles
- Edges are rolled for strength and to avoid cuts
- Easy to cut out holes for fuel lines and control handles
- Can be folded up for packing, but best rolled around a smooth bottle