by Tim Clarke » Sun Jun 24, 2012 3:06 pm
Hi Walker Woods and forum members,
I'm Tim Clarke from down under(Australia). I am an older citizen who is still young at heart and very active in extended hiking and skiing trips. This is thefirst time that I have tried to participate in any disussion forum, so please be gentle and patient with me as a novice.
I have been developing wood burning stoves for tents for warmth while camping during snow ski trips and mountain hiking. My main emphasis has been on light weight stoves (as light as 150g stove and 150g flue) that can pack down to the size of a can of baked beans. My stoves are so small (compared with those that I have read about in your forum) that they may not fit within the initial project brief. My stove will only heat a small 2-3 person tent. They need to be fed with small broken sticks or pieces of cut wood (dry snow gum). For this purpose I have made handy bow saw that weighs only 150g that can cut timber up to Approximately 15cm dia. I carry a general purpose knife that I use to split these rounds of wood to make suitable fuel blocks. To maintain good heat output the stove needs to be topped up with fuel very 10-15 min. This may seem to be a hassle, but from my point of view it is no bother if you can stay as warm as toast in a tent and what else can you do in a tent on those long cold nights. My stoves have another forgiving characteristic in that they burn slower as the fuel runs down for up to 30min and boosting the fire back to full power is easy with right fuel selection. Unfortunately, this is well short of the original project targeted 1.5h burn time. I use titanium for the flue. Previously Iand I used aluminium for the flue which doubled as the single centre pole of the conical tent. This worked for several trips, but when the fire was given full air supply with high quality snow gum blocks the flue got too hot and it folded and collapsed and destroyed my companions air mattress and the ground sheet. Nevertheless, this little disaster was a good lesson and I went out into the bush and cut a substitute bush pole for the tent, while my companion became at temporary tent pole.
My favourite stove so far is one made with stainless steel, the inside of of a dead 'Stanley' vacuum flask which has a narrow neck opening that is compatible with the fitting of my small diameter (30mm) flue. This stove gives out lots of heat and most of it is given to the tent space. The stove glows red, while the temperature of the flue just below the apex of the tent is only about 100C. I am working on a 20g fan to better spread the heat around the tent and dry wet clothing. I have found that burning a low fire with fresh wood gives soot/tar buildup problem in the flue, this however is not a problem when the fire burns down naturally through the charcoal phase where ther is little or no smoke.
I have used the stoves in a 'Appytrail' tent that I modified to take a homemade flue jack. For many reasons I decided to make my own custom tent that I think is optimised for use with a stove. Features: silicon impregnated nylon ripstop fabric from 'Oware' , conical or 12 sided pyramid finishing in a 400mm dwarf wall and standing 1800mm high. I have made a spreadsheet that computes the panel sizes, given the fabric width and tent size. Most seams are double stitched lay flat seams (4 layers of fabric in each seam). The pyramid seams are cut and sewn in such a way that each seam formed with a straight-grain from one side and cross grain from the other. This means that all the seams have uniformly low streatch and in my experience do not need any reinforcing tape. Also, I have found no need to seal the seams as the silnylon repells water from the seam. The top of the tent has an adjustable hole in it for the flue and a strong cord in a hem is used adjust the circumference. A light weigt 60g aluminium gland goes throught the hole to make a safe exit for the flue. The gland is also the mount for the center pole if you have one or the mount for a hanging cord so that a pole-less erection is achievable. It saves weigt if the right type of overhanging brances are available and is my favourite as it makes the tent feel so roomy. The tent is pegged to the ground at 12 point, has 12 pull out cords at the top of the wall and another 12 pull-out 2/3 of the way down down the pyramid seam. Thes 36 anchor points make the tent very stable, even if a bit fiddly to set up. With a tent weight of 800g it was important to have very light tent pegs. I have found that I can make suitable pegs out of high-tensile fencing wire ( that ancient old hard stuff that I would never wish to use on farm fencing these days). If weigh is so important, you can use 12 pegs for the tent base and use sticks for the other tie-outs. Lastly, sticks layer flat on the snow and stomped in with more snow makes an excellent anchor under cold conditions. Above the tree line in melting snow conditions I have had even large aluminium pegs melt out and give way. For this situation I have made snow discs from soft drink can ends with hand rolled safety edges ( good job to do in front of the fire on a cold night). These discs have a cord with a ultra light weight (home made of course) 3-hole length adjusters (cord is the smallest one from the Oware range).
The tent can be erected as described above,but for high wind situations or for rapid emergency situations it can be pitched lower, so that it is a pure pyramid pegged directly to the ground and with pull outs on each seam. This makes a very low and stable configuration for surviving strong winds, even if there is less than ideal head room it is still quite adequate for 2 or 3 at a squeeze.
Regarding the cooking requirement of the stoves, mine is weak in this area, but I have managed to boil water and cook simple food in sachets held against the body of the stove,but this requires more refinment. Consequently, I have developed a little hot water service that goes on top of the stove (150g). This can make 400ml of boiling water in about 7 min. It could also be able to melt unlimited snow to make drinking water which I find so important when I go back country skiing. I suppose this is not a failure if you can manage with sachet cooked meals and lots of hot drinks and unlimited hot water bottles for the bottom of your sleeping bag. During my developments I found that I could get a much better burn and virtually no smoke if I have two air admission holes that both have very fine regulation. If you get the balance right you get complete combustion, lots oh heat high up where you want it and no soot in your flue or tar running down and making a mess.
Regarding the preference for stainless steel/titanium, for the flue I don't think we can do better if we can keep the titanium cost low ( mine rolls up so small that it will fit inside the cardboard tube of a good old 'sunny roll'. How small is that????
Please let me know if my messing about with stoves/tents is of interest to the forum, but I appreciate that my line of enquiry may not be in good alignment with those of the forum
Probably should get back on that.
I am a bit worried about the spacing of the bottom air holes. I think the air intake in the proto type might work better but not sure. I really like the door flap. I am going to be finishing up my tray stove (finally) and might steal the idea. The legs on mine allow the stove to sway a bit but that doesn't bother me too much and betting a snow platform with holes for the legs would take care of the issue. The taller pipe is a smart play as it should draft better and toss sparks farther away from the shelter.
