How much of an opening between firebox and cook chamber?

[busmania]

I’m about to start a 24” x 54” cooking chamber with 24” x 24” firebox (round). I’m going with a 5” stack at grate level and possible build one of those fancy collectors I’m seeing everywhere for the exhaust. My question is, how much of an opening from the firebox to the cooking chamber should I have? Currently I’ve designed the firebox to sit just above the center point from the cooking chamber (11” from the top of 24” diameter tube). My thinking is smoke will just roll right across at about grate level. Is this too much opening? I see super tiny openings and really big openings on builds around here. Thoughts?

 

[smokin peachey]

Try this. http://www.feldoncentral.com/bbqcalculator.html

 

[fivetricks]

daveomak

He always says that feldons has a flaw in their formula related to fb -> cc openings but I can't remember the exact issue myself. He should be along at some point :-)

 

[smokin peachey]

Here is a good watch.

BBQ with Franklin | The Pits | Episode 4 | PBS

For good BBQ you need a good BBQ pit. Learn the secrets.

www.pbs.org

 

[daveomak]

daveomak

He always says that feldons has a flaw in their formula related to fb -> cc openings but I can't remember the exact issue myself. He should be along at some point :-)

Feldon's uses the FB size to do all the calculations.... the Cook chamber is the determining variable when building a smoker and we use that number for doing all the calculations...
Basically Feldon's is a very good calculator... They assumed a few things that needed updating and we did that...

 

[Alphonse]

Feldon's uses the FB size to do all the calculations.... the Cook chamber is the determining variable when building a smoker and we use that number for doing all the calculations...
Basically Feldon's is a very good calculator... They assumed a few things that needed updating and we did that...

Can you tell me where to find the updated calculator?

EDIT: found it the reverse flow section

 

[daveomak]

Standard Reverse Flow Smoker Calculator... by DaveOmak and others... Ready to use.. rev5.. 6/19/15.

Here's to "Alien BBQ" and the folks that first put the calculator together and "1728 Software Systems" for this great "Circle Calculator" and all the folks at "SmokingMeatForums", with a special shout out to Ribwizzard, that contributed their ideas and feedback while this thing was coming...

www.smokingmeatforums.com