# Need help with traditional flow offset smoker build

#### Sietseweg

##### Newbie
Currently i am building a traditional flow offset smoker, i have a few questions about the numbers. I read a lot of negative things about the feldon calculator and would like to double check with you :)

My setup:
264 Gallon propane tank

Firebox made of steel tubes 3.15 inch x 1.18 inch, we have the tubes and don't know yet what size firebox we are going to make (i think inner size 26 x 29 x 29 inch)

Chimney diameter 6.5 inch diameter, not yet cut to size.

Does the opening to the cooking chamber have to be on the upper end of the firebox, or can it also be in the middle (so we can mount the firebox a bit higer)?
Does the opening have to be round or half moon or can it also be square?
What is the recommended size for the opening? (if feldons calc is not right)

The chimney will be connected to a collector in the middle of the tank, should i take the recommended size from the top of the tank or from the lowest point of the collector?

Here is a link to my calculations:
Link to BBQ Pit Calculator

I hope you can help me out with the numbers so we can build a good quality smoker :)

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#### HisMajesty

##### Newbie
I'm no expert but I believe that if you don't have the opening at the top of your firebox into your cook chamber you will trap an enormous amount of heat on the top side of your firebox. I think that would also significantly raise the temperature in your cook chamber on the firebox side.

#### unclebubbas bbq

##### Smoking Fanatic
Your fire box is plenty bib enough, the opening in it should be at the top and the shape of the opening does not matter. The size of the opening should be approx 1/3 of the size of the firebox end panel. 6" stack is also plenty big enough. Are adding a baffle plate inside the cooking chamber above the firebox opening?

#### Sietseweg

##### Newbie
Thanks for helping me out!
We will make the opening in the top of the firebox.
For now we have had no plans to make a baffle plate, would you recommend it?

how long stack size would you recommend?

#### unclebubbas bbq

##### Smoking Fanatic
3-4' long should be fine for a smoker that size, I have seen longer ones that are hinged for transportation

#### Sietseweg

##### Newbie
Thanks, would it be 4 feet from the collector or from the top of the tank?

Above the tank

#### unclebubbas bbq

##### Smoking Fanatic
The baffle plate helps to distribute the heat a little more evenly across the cook chamber, without it my guess is that there could be a 50 degree temperature difference from one side to the other

#### Sietseweg

##### Newbie
Ah Yes i think i will make a baffle plate then! Thanks for the tip!