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

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Square vs Round

Volume on square tubing (Stack) is figured this way:

Tubing size let’s say  4 inch and 20 inches long       so 4 x 4 = 16 x 20 long = 320 cu. in.

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Round Tubing (Stack)  is figured this way:

V= π r2 h

Say we have a pipe that is 4 inch dia. and 20 inches long

π = 3.1416

r = radius ( radius is ½ the diameter   ----  2

2 = Dia. x Dia.                                              -----  2x2 = 4

h = length of the pipe                              ----- 20

3.1416 x 4 x 20 = 251 cu. in

So a 4” round and square do not have the same volume

A  4” round stack would need to be 25.5 inches to have the same volume as a

 4 x4 x 20 inch  square stack
 
Gary......  volume and effective diameter are not the same.....    SmokeJumper noted the hydraulic diameter...   Hydraulic diameter of a 4" square tube is the same as the hydraulic diameter of a 4' round tube...   You are mixing apples and oranges...  
 
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I understand Hydraulic diameter Wasn't trying to disagree with Smoke Jumper (Sorry if it came across that way)  Just wanted to make sure Ink.  understood the difference between the square and round volume .

Sorry Smoke    now I have my apples all in the same basket.

There are lots of people on here that don't build stuff all the time, they may build one smoker and that's it.  I try to give examples and keep it simple so everyone can understand.

Gary
 
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Hey Dave, good to hear from you, you haven't corrected me in a long time, I was getting worried !!   Hope you had a great Christmas.

Have a Happy new Year

Gary
 
Dave

Thanks for your reply but I am totally new to the art of smoking meat and have only tried my old Char Broil grill once with little success, so all this does is make my head spin.

Steve
 
For folks wanting to build a Reverse Flow Smoker, this thread was put together for them, so they wouldn't fall into some misinformation about "How to build"....  It provides proven calculable dimensions for a smoker that works... 
 
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Dave this thread is awesome. Maybe I missed it but I was wondering, when building a 250 gallon RF should I put my stack on the end with a plenum or on top of the cook chamber?
 
What ever fits your design...  Some folks think the top of the CC is best, others think the exhaust exiting from the food rack height is best...  Depends on the tank and food rack locations... 

If you want a warming oven, the stack can be incorporated into it's design.. 

Did that help ?? probably not...    Build the smoker so it's the best smoker it can be and forget all the bells and whistles..  You want great food first...
 
Why not do both, Have the looks and a great cooking smoker. No reason to give up one for the other. Take your time Research, research, research. Then incorporate the look with 

the calculations. No reason to have an ugly smoker. You will want to show it off and how well it smokes

My 2 cents worth

Gary
 
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My tank is 30" O.D. (29.5" I.D.) X 108" (9'). I'm cutting 27" off one end to use as FB the other 81" will be my CC. I plugged all the numbers in using the calculator and think I should be good. Just wasn't sure if there's a benefit to stack placement (top or with plenum). As of right now I will not have a warming box. But that could change...lol I have a tendency to do that. Thanks for the help!
 
Volume in cubic inches x .001 for air intakes...volume of CC? FB? if this has already been covered I apologize. Perhaps I just missed it...
 
My tank is 30" O.D. (29.5" I.D.) X 108" (9'). I'm cutting 27" off one end to use as FB the other 81" will be my CC. I plugged all the numbers in using the calculator and think I should be good. Just wasn't sure if there's a benefit to stack placement (top or with plenum). As of right now I will not have a warming box. But that could change...lol I have a tendency to do that. Thanks for the help!
You will be better served if you start a separate thread on your smoker build....

Stack placement...  I would go with the plenum...  That opens up more room for food racks...  Place it about at the center of the top food rack....  Doing so, it will draw air / smoke / heat from the center of food placement...  OR, reading about what results others have noticed by their stack placement is a good way to figure it out....

 
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Hello all,

I've build a reverse flow smoker and I came across this thread. I saw Dave Omak mentioning the following:
http://www.smokingmeatforums.com/content/type/61/id/353358/

I didn't install the upper vent in the FB see pic:
Would you recommend me to install it?
I also have a 15/20 degr temp difference left to right, hotspot at the FB.
Thanks!
Upper air inlet ??  YES...  folks have noted more uniform temps across the cooking surface AND reduced fuel consumption...
 
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I just wanna say that I just bought a standard offset smoker for cheap and after using it once and seeing the 30-50 degree temp difference across the CC I desired to go to reverse flow. I used these calculations and the smoker came out great I did not add extra air vents to the fire box but I may try that this weekend. I just want people to know these calculations worked great I got and even 2-10 degree temperature across my CC it was amazing. I did get alittle fluctuation when stoking the fire being new to the reverse flow style but it the temps stayed consistent with one another if the fire out side raised 5 degrees so did the opposite side. Thank you for this write up was the most help out of all the research I found on this subject
 
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