So here's what the finished product looks like. I cooked a picnic shoulder and a rack of baby backs Saturday night. I had trouble getting temp much past 160. I used two Weber charcoal baskets designed for offsetting the coals from the meat in a kettle grill. I kept piling on pre-lit coals, but couldn't get the heat up.
The chimney drew beautiful blue smoke. That's a plus.
I cooked the meat for about 13 hours; then, we finished it off in the oven for an hour at 350 (less time for the ribs). It was delicious and smoky, but the picnic shoulder didn't pull well.
Weekend after next I'm going to be cooking for somewhere in the neighborhood of a hundred folks. (Not on this rig alone.) The oven is going to be *very* busy with side dishes, and finishing off several roasts will not be an option.
So here are things I know I can (and will) do:
- Glue some heavy-duty aluminum foil (or something stronger, if I find it) with RTV, across the openings intended to accommodate a rotisserie. Obvious point of thermal loss there.
- Glue some exhaust header wrap over the gap between the top and bottom halves of the cook chamber. (Again, using RTV.) I layered several strips of Nomex gasket material in there, but there are still gaps. I think the wrap, "taped" along the back, would help there.
- Get a bigger coal basket than the two little Weber baskets. They're shaped in a way that doesn't give maximum efficiency to the burn, though they did keep the coals from falling to into and being smothered by their own ashes.
- I don't know how pliable the material is in the charcoal tray (shown in this photo drilled full of holes, reverse of its intended orientation, and laid in the chamber instead of hung from the grates). Pretty sure it's sheet steel. If it is pliable enough, I want to flatten the angle of the bends along the sides of the tray, to make it catch the sides of the cook chamber higher up, and hopefully, let more heat into the chamber.
- Drill more holes in the charcoal tray-turned-heat-channeler, to try to free more thermal energy into the cook chamber.
Going to try all of the above steps. If that doesn't work, I'm falling back on a solution I came across on another forum, where the guy used an aluminum foil pan for a baffle (note my baffle in the photo) and then aluminum foil cookie sheets as "tuning plates". He claimed great success with that setup, as far as keeping the heat and smoke even across the chamber.
If all else fails, I may re-visit the duct as a way of keeping thermal energy in the cook chamber higher. I'm no physicist, but it seems to me that if the heat can't run right out the chimney at the top, and has to instead exit at grill point, a higher-temperature stasis might build up right about grill level,