After viewing several "models" of wood gas and alcohol stoves for camping I came up with this idea of a Hybrid Wood gas- Alcohol stove which is lightweight and it fits in the backpack without staining anything at all. I must apologize for not having a picture of the inside can, but since the first time I inserted it on the big can I had tight fit issues, when the one you see there fit perfect, I didn't want to risk removing it to take the picture and compromise the good seal it has. Again apologies for that detail, but I hope the pictures are clear enough for you to understand.
Step 1: Building the Wood Gas Stove.
The gas stove is very simple really. I found a 1/2 gallon can and a "tall" 1/4 gallon can, which in my country are hard to find, but finally found one.
Having the 1/2 gallon can upside down, mark the diameter of the 1/4 gallon (in my case was 10 cm) as centered as possible. I marked 12 mm all around. The next step is to draw yet another circle inside the one already made, in order to make a good set of tabs to seal the inner can inside the outer can. (See figure 1)
After you draw the three lines, cut at the inner line, sand the edges that are going to be quite sharp, and using a triangular file make "v's" like the ones shown. (See Figure 2). Additionally, drill 16 1/2" holes at 1 cm from the top (remember the inner can is inserted on the bottom of the big can, that is, upside down). That is all for the 1/2 gallon can.
Step 2: The Inner Can.
For the inner can, find a "tall" can where a tuna fish can will fit precisely but without having to press too much and where the tuna can will not go in. In my case I found a "Milo" light can which is a chocolate mix. On this can, drill 16 1/4" holes at 1 cm from the bottom, and 8 1/4" holes at 1 cm from the top (the ones on top are shown in Figure 1. Unfortunately the ones on the bottom are difficult to show). Additionally, at a scrap yard, find some thick perforated cold rolled sheet (I find it more resistant than the steel mesh I have seen in some projects) and make a mesh that will be bent as shown in Figure 2. This mesh should stand a little above the bottom holes of the can in order to allow the air to flow up and the ashes to fall down below the holes and on the bottom of the can. Once this piece is finished and placed in the can it will look like in figure 3. The inner can is finished. Now, insert it on the outer can on the tabs prepared for a good seal.
Note: This step is very important. Be very careful how you insert this can inside the other. Be patient. Turn the big can and try to insert the inner can in several positions while being slant in order to accommodate the tabs into position. Once all the tabs have been "bent" insert the inner can in a slant position and press a little harder until it goes "in". Then, press on it until it is seated inside the big can as in Figure 1, and it rests on the edge, while pressed by the tabs in position. Once it is in position, it should look like in Figure 4 when looking from the bottom.
Step 3: The Pot Stand and Feeder Hole.
With the same perforated sheet used for the inner can, make a pot stand that will be placed on top of the stove to allow for the wood to be fed into the stove while the pot is in position on the stove (Figure 1). When this stand is finished, it can be inserted in the bottom of the can when not in use, as shown in Figure 2, for storage.
Step 4: Preparing the Alcohol Stove.
In order to have an alcohol stove, get a regular tuna can, and drill two lines of 16 holes each just below the open end, without aligning them up in order to get a good combustion. Also, to be able to put it on top of the wood gas stove you need to make a small triangle to support the tuna can.
Step 5: The Stove in "Alcohol Mode"
This is what the stove looks like when used as an alcohol stove. The triangle is placed on the rim of the inner can, and the tuna can is placed over it. There is no need for a pot stand in this mode, as the tuna can does both jobs as a stand and as an alcohol stove. (See Figure 1).
Step 6: The Stove in "Wood Gas Mode"
Here, the triangle and the tuna can are removed, wood twigs are then inserted in the stove and lit. The pot stand is removed from the bottom of the stove and placed on the big can rim, to place the pot and allow the twigs to be fed while the pot is on the stove. (See Figure 1).
Step 7: Storage and Packing.
When you are finished using your stove, place the triangle inside the inner can, the pot stand in the bottom of the stove, the tuna can inside the small can, and cover. You're good to go.
I hope the steps are clear enough to understand. If you have any questions please don't hesitate to ask.