I did another "dry run" burn over the weeked after implementing the mods (vent stack extension, silicone sealant, charcoal grate, and dual thermos at grate level). Ambient temps in the mid 80s and wafting breezes up to ~10mph. I started the burn with the smoker under a tree, but moved it into the sun after an hour. A couple of things:
Observation: It just didn't draft anywhere near as well as my first couple of runs.
Conclusion & Steps Taken: My guess is that the vent stack extension is too long and stifles draft formation. I decided to remove the end piece to get the exit a little further away from the grate level.
Observation: I filled the charcoal basket (10" x 10" x 6") with good-sized pieces of Cowboy brand lump charcoal (never buying this bag of splinters and dust again...), made a little crater in the pile, started a full chimney with more lump, let it ash up, and loaded it into the firebox basket ala the 'minion method'. Stack vent and intake vents were both left all the way open for the duration.
I just could not get grate temps above 200-205F. After a couple hours of this, I guessed that the basket was just too small for such a large chamber and, to test my theory, I removed it, letting the coals kind of fall loosely into the firebox. This started my temps to climb gradually and was able to reach ~230F at grate level (which corresponded to ~300F+ on the top gauge... what a joke that thing is!)
Conclusion & Step Takens: You can definitely make a basket that has too small of a surface area for the internal volume of the cook chamber. It just can't keep up unless you have a HOT fuel source. Dissassembled the charcoal basket, rebent the arms out, and reassembled it. It's dimensions are now 10" deep, 11.5" long, and 6" tall. I also found that sliding the basket closer to the intake vent side allows me to add my chunk wood on the outlet side which REALLY helps with heat production.
Observation: Compared to my first runs, very little smoke escaped from the cooking chamber.
Conclusion & Steps Taken: That Rutland silicone sealant is the bomb. I need to add some more thickness in a few spots, but it totally sealed up the firebox joins and did a great job minimizing the loss through the cooking chamber door. My two grate thermos, which are 13.5" apart, were within 5-7 degrees of each other. Nice. I was lucky though... the fitment out of the box was pretty damn good.
Question: Does anyone see any benefit to adding another air intake to the firebox -- maybe above the existing one -- to help with getting temps up? I'd like to be able to get grate temps up to 275-300F if I want to. After the firebox sealing, I think that my fire chamber isn't getting enough air now! Can one actually seal these things up too much? When I'd open the firebox main door, the coals would burst into flame.
Question: In breezy/windy conditions, do you guys point your firebox air intake vents toward the wind, away from it, oblique to it, or does it matter? I'm hoping my vent stack extension cutback will solve this, but I was actually getting smoke wafting out of the intake when the wind luffed...
Edited by Remmy700P - 7/31/13 at 9:34am