Smokestack/Exhaust Size Question

I've got a question, and I've done a search on the forum but maybe I'm not searching on the right key words. I'm doing some mods to my smoker: insulating and double walling it, and turning it into a reverse flow. I've been using it for a couple years as a traditional offset, exhausting it through a 4" at the end furthest from the firebox and 2" at the end nearest the firebox, both stacks about 24" long. The tank dimensions are 5' long, 3' diameter, with a large offset fire box. So my question is: With my mods I am changing the location of the smokestack, is there a "rule of thumb" calculator that will tell me the diameter and length of my exhaust pipe to get adequate draft? Thanks for the help.

jonboy said:

You might want to post the size of your smoker.

Click to expand...

The size of the smoker is in my original post.