The Double Oven Smoker is now complete and functional.
The blast gates work well as vents. There is one on each side of the firebox, and one at the base of the chimney.
Each 4" hole drilled through the walls of the stove went through the inner enameled steel shell, fiberglass insulation, and the outer steel shell. The drill bit was a 4 1/8" bimetal hole saw from the Depot, which is the perfect size for 4" stove pipe. (The drill was an vintage 1/2 inch 2 handed drill from the 1930's that once belonged to my grandpa George - this is exactly the kind of crazed project he would love) To prevent smoke and grease from entering the interior insulation I lined each hole with 4" stove pipe, used stove gasket rope as a seal and used self tapping screws to secure the pipe to the shell via tabs cut into the pipe.
I drilled 2 4" holes between the firebox and the smoker, one would have probably been sufficient.
There is a need to adjust the openings between the firebox and the smoker. for now, I settled on magnetic part trays from Harbor Freight, they are just the right size to use much like drain stopper in a tub. Just be sure to remove the rubber covers.
It would be nice to come up with a way to do this with a lever from the outside.
So far, I have placed a thermometer on the side of the smoker section.
The entire shell was painted with flat black stove paint.
The firebox is bigger than it needs to be, I have added a number of heat bricks to it to fill in the space.
It holds heat at about 220 with a small fire if you keep it tended, it will drop back to 180 for 3-4 hours untended. With a larger fire (defined as a full load from the standard charcoal starter, the heat will easily go to 400 + in the smoker, not something you want vry often.
I need to do more tweaking of draft and fire size to get it to hold at 230-250.
The smoker burns less fuel than my old 2 door brinkman. It is very well insulated, since fiberglass is packed between the inner and outer steel shell. It loses very little smoke at the seams between the upper and lower chambers.
The budget was naturally overrun, mostly due to the need to buy some expensive drill bits. Parts came to about $120. The 4 1/8 hole saw added another $55. The stove itself cost just $37.50. I made back about $15 selling stove parts on Ebay.