A 31 g lay flat kettle boiling on wood fired ultralight tent stove. The stove is mounted on bush poles above the snow in a snow pit that is formed inside an ultralight tent.

The slim oval ultralight tent stove (~950 g) for winter trekking has large cooktop for 2-3 pots for snow melting, boiling and cooking. It cleanly burns ~410 g of wood/h and has an estimated heating power 890 watts.

Introduction

For some time I have been using my small ultralight tent stove for alpine backpacking adventures as a source of warmth and cooking in an ultralight tent. Building on this success, I have sought to develop a similar but larger stove that works on the same unusual inverted burner principle that makes a hand full of bush sticks burn efficiently, systematically and cleanly to produce abundant and intense heat.

Larger ultralight tent stove

Large ultralight tent stove warming seven snow trekkers. The fuel sticks in the tube (on the right side) reflect a small glow from the burner as they are being dried by the intense heat from the burner. However, dry sticks are needed to start the burn.

My slim oval tent stove is ~40 mm thick and has an oval cooktop that is 240*400 mm. It makes a versatile cooker with a backpack friendly shape. At about 950 g it is ultralight if it is to be shared by a group of trekkers. At camp, the 50 mm diameter flue pipe connector ring can be inserted and then fitted with a 2,000*50 mm dia roll up flue pipe. Similarly, the 60 mm flue mount ring can be inserted to hold the 180 mm long fuel stick holder/burner assembly and lastly the primary air port and slide valve can be inserted.
Conical connectors in stove top. The external taper facilitate easy entry into stove top and also ensure a tight fitting between the connector and the stove top. Similarly, the internal tapers easily dock and seal with fitted tubes.
Conical connectors in stovetop. The taper on the fittings facilitate easy entry into stovetop and also ensure a tight-fitting between the connectors and the stovetop. Similarly, the internal tapers easily dock and seal with fitted tubes.

Stove mounting

Off snow mounting. The stove can be mounted in many ways. Off the snow, it can be mounted on the ground that id cleared of combustible materials. It also can be set on three rocks to keep it up of the ground and to set the cooktop at the prefered angle. My prefered option if possible is to set it up on a large slab of rock that is in turn set on three or more rocks. This configuration creates a hot bench for the tent to; dry fuel sticks, keep food and drinks warm and to dry socks, gloves and hats. Eventually, the underside of the rock slab will become quite warm and suitable for drying things. The last pleasure is that a large rock slab will act as a heat bank and radiate heat for hours after the stove has been put out. “This set up takes a little effort, but is very rewarding, particularly, if you are pinned down by bad weather for some time.

Deep snow mounting. The stove is provided with 6 clevis mounting devices that are welded on around the perimeter. At the camp, these can be connected to articulated mounts that can be fitted to stove legs made from bush poles. The stove legs can be driven into the snow to mount the stove at a comfortable height above the snow surface. An alternative fitting that connects to a tent pole can also be used as one of the three minimum support legs. With bush pole legs and a little clever twitching of nylon cord or cable ties, a wood drying/storing rack can be formed below the stove.

Stove mounting without a tent pole. My tents are designed to be able to be erected without a tent pole (see below). This means that there is great flexibility in the mounting of a stove, particularly on snow.

Individual ultralight stove mounts & pins (~6 g each). The mount on the left has the hinge pin securely stored in a pocket welded to the mount. The one on the right has the pin deployed in the position required for mounting the stove.
Individual ultralight stove mounts & pins (~6 g each). These mounts fit onto bush poles that can be driven into the snow to make stable stove legs. The mount on the left has the hinge pin securely stored (for backpacking) in a pocket welded to the mount. The one on the right has the pin deployed in the position required for connecting to the stove clevis mounts. They connect to matching clevises that are welded to the stove body.
Ultralight tent stove with four stove mounts connected by titanium pins to four of the six low profile clevis fittings that are welded to the stove perimeter.
Ultralight tent stove with four stove mounts connected by titanium pins to four of the six low-profile clevises that are welded to the stove perimeter. The six clevises allow for a flexible arrangement of stove legs according to tent layout.
An alternative ultralight tent stove mount (~7 g). It can be twitched to a tent pole (if there is one) with a small stick that is held from counter rotating with a rubber band . This can be effectively used with two other stove supports provided by bush poles. The inside of the clamp ring is coated with soft silicone rubber to provide a good grip on a metal pole.
An alternative ultralight tent stove mount (~7 g). It can be twitched to a tent pole (if there is one) with a small stick that is held from counter-rotating with a rubber band. This can be effectively used in conjunction with two other stove legs made of bush poles. The inside of the clamp ring is coated with soft silicone rubber to provide a good grip on a metal pole. The connecting pin is stored in a welded pocket on the fitting.

Field testing- time for procrastination was over

This prototype stove had many bench tests but had never had a real field test in the snow and I have found that such field tests in the snow, are the harshest ones and usually reveal design deficiencies and areas for improvement. I also find such tests are easy to put off.

“Success is nice, but failure is a better teacher, and such learning is never immediately a nice experience.” Consequently,  I was leading an annual snow camp for the Strzelecki Bushwalking Club at Mt. St Gwinear. We had exceptionally good deep snow for the event (for skiers and some snowshoers). I could procrastinate no longer about the field testing even at the risk of failure in front of a small audience of vocal ‘die-hard’ snow campers.

I took my large ultralight tent and erected it, without a pole, using a suspension cord from an overhanging snow gum branch. In the tent, we excavated steps leading down to a large snow pit so that we could walk into the tent with a central stove and sit around it the on the snow bench, on blue sealed cell foam mats, (with ski boots on). This made a comfortable heated communal shelter for the group to melt snow, make dinner, have hot drinks, share stories, and exaggerate the skiing exploits of the day.

In the middle of the pit, I mounted the stove on four long bush poles that were driven into the deep snow. These dead snow gum poles were selected and cut (using a 150 g DIY bow saw) to have ~30 mm diameter tops that would fit snugly into the four insulated stainless steel stove mounts. These mounts are loosely pinned (at the campsite) to low profile clevises that are welded to the stove body. The clevis and pin hinge arrangement allows considerable flex in the stove mounts so that they can align themselves with the irregular orientations of the bush mounting poles. Having removable mounts makes the stove body a ‘pack-friendly’ shape. 

Large ultralight tent stove warming seven snow trekkers. The fuel sticks in the tube (on the right side) reflect a small glow from the burner as they are being dried by the intense heat from the burner. However, dry sticks are needed to start the burn.
Large ultralight tent stove warming seven snow trekkers. The fuel sticks in the tube (on the right side) reflect a small glow from the burner as they are being dried by the intense heat from the burner. The tent is suspended from the branch of a tree and has a large snow pit dug in the middle. The stove is centrally located in the pit.

Stove assessment

The lager slim oval ultralight tent stove packed nicely in my backpack and it was a great success in keeping us warm and allayed my concerns about the failure of the field test in front of the group. The larger cooktop could easily heat multiple pots. The larger stove body seemed to have a lower temperature than the smaller stove, but it also seemed to radiate a lot more heat and the flue pipe temperatures were much less (only 100 degree C at ~500 mm from the stovetop)  than those on my smaller tent stove.  The flue pipe was not uncomfortable to touch where it was about to pass through the flue gland. This means that the larger stove is probably more efficient at radiating more of its heat into the tent. The larger stove burnt 410 g/h of wood which is only marginally more than the smaller tent stove. The 60 mm dia fuel tube (c/f 50 mm for the small stove) provided easier fuel loading, allowed the use of thicker fuel sticks and provided a more stable burning.

The stability of four leg mounting of the stove was better than the one leg design for the smaller stove and there was no concern with the cooktop sagging when a big load of cooking was placed on it. My companions repeatedly commented on how clear the flue emissions were, there was seldom any sign of smoke and this meant that the combustion was clean. complete and efficient. The stove sometimes made a gentle chuffing sound that on one occasion coincided the distant sound of a helicopter, but it was by no means unpleasant. Once started with some dry sticks, the stove worked well with directly collected dead snowgum sticks that were quite cold and damp.

Deficiencies that were revealed were that the flue pipe needed to be anchored down to the stove body so that it could not be bumped off. The fuel stick/burner tube needed a more substantial mounting.

There was an occasional problem of the burner becoming choked with ash and charcoal, but I think this could have been due to the inadequate connection of the flue pipe.

Under the cold conditions the stove was a little harder to start and with a snow pit and wearing stiff ski boot it was difficult to get down to gently blow into the primary air port (as I usually do). A USB fire blower should be a useful tool to deal with this situation.

Lastly, the stove would probably be better mounted on only three legs (rather than the four as in the photos) as this would make the mounting much easier and just as stable. Luckily the stove has six possible mounting clevises on it so this should be easy.

Tim

gge

4 Comments

  1. Hi Alan, What is the diameter of the pot shown on your tent stove in the BPL article https://timtinker.com/ultralight-tent/. I am just interested in the scale of your stove compared with mine and would like to put a pot of similar size on my slim stove and see what room is left for other pots and kettles etc. I am not being competitive mind you!

    Your comment about snow melting is so important as it can allow you to camp away from water where the skiing is the best and you can do the snow melting while cooking dinner if the cooktop is big enough.
    Regards,
    Tim

  2. Hi Alan, Sorry for the delay in replying/commenting on your great project described on the BPL forum. I skipped through most of the detail, but was excited to see that you had faithfully emulated many of my ideas and from the photos of the burning stove you were getting a lot of heat out of it. I will read with interest all the details later……and respond to your detailed questions. I still feel as though I am JUST a step ahead of you on design with my slim large stove that you have read about in this post and you can see from the photos that it makes a great cooking/heating platform for snow based camping and makes a nice slim pack friendly load.

    “It is great to be an inspiration to someone other than myself”

    Will keep in contact.
    Tim

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