I made a very similar smoker. I am having trouble getting my temperature up and keeping the firing burning. I got to 138 degrees and that was all. I don't have a damper on my hot box but I don't see anyone else having one either? Any insight to help get me ready for my first smoke would be greatly appreciated! Thanks!!
Fire control takes to air inlets to the fire box..... upper and lower.... and an outlet for excess heat.... and inlets and outlets on the smokehouse for great temperature and air control..... the design below just explains the theory... actual controls can be designed in many ways....
I designed and built my smoke house based on a similar design to yours. The outside dims are 4'X4' x almost 6' high. I opted to use T1-11 siding and sealed and insulated the smoke house with 1" foil faced insulation board. The chimney is a 2" pipe with a slide plate on top for control. Air inlet to the firebox is a 4"x8" hole in the lower side wall with a steel slide plate for air flow control. The fire box is directly next to the smoke box and the smoke and heat passed through another 4"x8" hole in the adjourning wall.
Now to your question about reaching cooking temperatures. I also have problems getting the smoke house up to cooking temperature. I found I have to open both the inlet and outlet controls fully and even when building the fire, I need to open the firebox door in order to get a good fire going. I can not rely on lump charcoal or a small amount of wood to get enough heat into the smoke house. Once I get a good fire going I can close the firebox door leaving a slight gap and then the smoke house temp will rise. I can get 225 to 250 this way, but it takes quite a while to get there. However, once there, I can close the firebox door completely and the smoke house holds the temp well as long as I keep adding wood to the fire.
If I smoked a lot of food at one time it would not bother me. However, for small amount of food, or for food that only requires a short cook time, it seems I need to use a lot of wood. It is unfortunate I have to buy my wood.
To answer TXDVR. I am a newbe at smoking, but not at at construction techniques as I have over 50 years experience as Civil/ Structural Engineering Designer.
Structurally you need to support your smokehouse on a proper foundation if it is a permanent structure, similar to the one being discussed in this thread. A slab foundation is OK but will increase the height of the smoke house if the slab is at grade. A better approach is to build concrete footers and and masonry walls, filling the interior space of the foundation with a concrete floor. This design can lower the structure into the ground keeping the height more reasonable.
In my opinion, if you are creating in effect and "oven" it needs to be insulated or all the heat escapes. I good choice for insulation is a foil faced hard foam board 1" thick or more. The insulation also protects the wood construction from any concerns from excessive heat creating a fire risk. Once the smoke house is used a few times the smoke will cover all of the interior surfaces with a coating of creosote forming a protective barrier in itself, so I can not see any advantage to using expensive wood such as cedar other than for exterior appearance and weather durability. Sheet material, such as primed T1-11 will work just as well, but will need to be painted.
And of course, you need airflow control both in and out. From what I can determine, a chimney damper is not a must, but I opted to use a commercial smoker accessory supplier steel pipe chimney with a slide plate that can close the outlet. This does two things: 1. provides some degree of Temp control and 2. prevents, when completly closed,any chance of rain or creatures from entering the smoke house.
Not an answer to any question but just a note. I found the more difficult problem to solve was how to keep the smoke from seeping out around the smoke house door and the firebox door. Even expensive gasket materials doesn't seem to do the job. I have minimized leakage but have not been able to eliminate it.
My smokehouse Pix. If I had a do over, I would make the fire box a little larger. Have eliminated some of the smoke leakage around the lift up fire box access door with additional gasket. Smoke stains are from early usage.
Do not use the foam insulated board. It may give off a toxic gas. Use 1000 degree spun glass insulating board. It comes in 2ft by 4 foot semi rigid pieces and you can get the in 1 and 2 inches thick. It will not fall down and will last forever. It was about 100$ for my 3 ft deep by 6 foot wide by 5.5 ft tall smokehouse and I can cold or hot smoke to 500 degrees if I want. I do have a gas burner in it but you should easily keep around 300 plus with wood on his design but he might have to extend his smoke stack to get the proper heat draw. The shorter the stack the harder it is for the heat to travel to the smokehouse. You might need to install a damper in the stack and run the vents on the firebox door wide open and go from there. IMHO but been doing this for years. Beautiful smokehouse and I'm sure you will enjoy it for years to come. Involve your family too. Summers are great times and the drinks are cold. Let your neighbors bring it they will be over to check it out anyway!
I am blown away by this design. I can't wait to build one for myself! I have been reading a lot about getting the right temperature with this. I think for cold smoking I will make the distance from the fire box to the smoke chamber a little longer, like maybe 8 -10 feet. For hot smoking, I think I will make the base of the smoke chamber another fire box, where I would most likely use charcoal as fuel and wood chunks for smoke. As mentioned before, small vents on the sides instead of a chimney on top to let excess smoke out and reduce the chances for condensation to drip back on the meat.
Truly amazing design. This thread is a gift to mankind!