Flat pan question? How much gap under rear pan?

[Sugarmaker]

Folks,
In helping neighbor ( Keith T.) with his new arch he is going to be running a flat pan this season. The rear pan 30 inches wide x 48 inches long. How much air gap should he have under the pan? Currently he has about 8 inches due to the fact he will eventually put flues in this pan. Should he cut this down to 4 inch gap under the pan to retain heat or build a dam at the backend near the flue?

Regards,
Chris

[vtsnowedin]

I would want the gap to equal the area of the stack or just a bit more. If you had a 12" round stack that would work out to four inches for 30 inches wide. Where you put the ramp or wall to narrow the gap to four inches would depend on your size of wood and the length of pan. You want the draft to flow through all the wood then rise up and strike the pan then follow it to the end staying close to the pan bottom. With a four foot pan two foot wood would work pretty well and the ramp should come up about 2.5 to 3 feet back. Just my .02:)

[swierczt]

I have a 25" x 34" pan with an 8" stack. I came up to within 1.25" of the pan for the back 18" of the pan it it works great. I am only loading 8" to 12" wood no bigger around than my wrist and I get a good hard boil with no issues of smoke backing up. This worked for me. As a note, I also have an airtight door and air injection below and above the fire. This may contribute to the forced draft, but from what others tell me don't be afraid to get right up close to the pan.

[Sugarmaker]

ooopps I didn't explain very well. Keith also has a 30 inch wide by 36 inch long pan in front of this flat rear pan and that is where the fire box is.
I like the 4 inches x 30 inches wide idea. thanks, I will let him know to reduce this gap and not waste wood.

Chris