Questions for building an offset smoker???

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milton1allen
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Questions for building an offset smoker???

Postby milton1allen » Wed May 18, 2016 3:21 pm

I am thinking about building an offset smoker and have lots of questions... I am thinking 20 or 24" diameter x 48" long with a firebox the same dia. as the chamber x 24" long. How do I know size and length of pipe stack for proper draft? Where on the end of the chamber do you weld top of firebox? Is the top of firebox in center of chamber? What size opening will I need in bottom end of chamber where the firebox mounts? I hope these are not stupid questions but I would like to build it correctly. Thanks for any other input you may have on dimensions to make it more efficient. Thanks...
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Finatic
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Re: Questions for building an offset smoker???

Postby Finatic » Wed May 18, 2016 3:45 pm

Not stupid questions at all. The answers to those questions will determine how well your new smoker will work. Here's a link that k.a.m. has posted in the past that will be helpful.

http://www.feldoncentral.com/bbqcalculator.html
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brentski
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Re: Questions for building an offset smoker???

Postby brentski » Wed May 18, 2016 7:50 pm

I used that link to build our trailer pit and it worked great for us.
milton1allen
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Re: Questions for building an offset smoker???

Postby milton1allen » Thu May 19, 2016 12:36 pm

Thanks for the link to calculations. I am guessing that the calculation on the firebox size is supposed to equal 100% size differential. I am also a little confused on the air intake diameter? Once I figure it all out theres no stopping me then!
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Finatic
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Re: Questions for building an offset smoker???

Postby Finatic » Thu May 19, 2016 1:12 pm

milton1allen wrote:Thanks for the link to calculations. I am guessing that the calculation on the firebox size is supposed to equal 100% size differential. I am also a little confused on the air intake diameter? Once I figure it all out theres no stopping me then!

milton1allen- For me I wouldn't worry if you are over the 100% differential mark on the firebox size. There are a number of things that can make that calculation vary. If you are at 150% to me that's not a bad thing. For the air intake, if you are using a 24"x48" pipe for your cooking chamber and a 24"x24" pipe for your firebox you'll need 32.54 square inches (I would round that up to 33 square inches) of air intake on the firebox. If you wanted to make a rectangle opening in the firebox the dimensions of that opening would need to be 8-1/4"x4" (of actual opening not blocked by a sliding door plate). If you wanted to make a round opening it would need to be 6-5/8" to achieve the 33 square inches of air intake. Again there are factors that can make the air intake calculation vary some. My firebox has an over sized air intake (I'm rougly in the 150% differential) and there are times when I've had the air intake wide open (mainly when I'm starting my fire or re-starting it after it burned down). I believe it's better to have a little extra air intake and chimney size.

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