We're designing a rocket stove for our house with a mass heater bench and bench-back built of cob and brick (we have lots of free brick from craigslist). The house is made of wooden stud construction, so we have left the barrel and burn tunnel 1.5' from any wood walls with insulation, shiny aluminum foil, and an air space behind it. I'd love feedback on the design, if you have some. This will be my first build, though I helped with one (mostly the cobbing, though). Not obvious in the drawing is the fact that we plan to surround the bottom 1/2 of the barrel with bricks (less radiant heat, but a little more child-proof) as well as 1/3 of the sides and the entire back that faces toward the wall. We would also put more insulation around the combustion chamber on the back side facing the wall, allowing most of the radiant heat to go in to the room.
Some feedback I already got was that we probably don't need so man twists and turns for the exhaust snaking through the brick/ cob wall. It goes back and forth 3 times each with the hope that it will be nice and cool by the time it reaches the top of the wall where it has less thermal mass between the pipes and the stud wall, but if fewer runs will work, and would leave more room for thermal mass, we can go that route too.
Some specific questions I have are what kind of radius do we need for the turns in order to keep a good draught. Also, would you recommend adding a pilot hole somewhere near the flue/ chimney to help create draught to such the smoke up before everything is really heated up so we don't have smoke back? If so, where would you put it?
Also, we plan to store adjacent next to feed barrel and wonder how much insulation or thermal mass we need separating the wood from the barrel so that the wood is nicely dried out but doesn't catch fire.
Any other feedback/ questions welcome!