Chimney Length

[blacktopbutcher]

I'm currently building a side firebox horizontal smoker and all my numbers have been working out based on Dave’s calculator. I just have a question regarding the chimney. I understand the need for length to obtain draft, however is there an issue with going with larger diameter pipe/length than what is required based on the calculator?

Case in point.(based on the calculator), if i choose to use 3.5" inside diameter pipe for the chimney the calculator gives me a length of 16" (above the CC). this is obviously to short. If I simply add the additional 20" in length will this cause poor draft characteristics? I’m almost thinking it may cool off to much prior to leaving the chimney but I'm looking for someone who has experienced this first hand. Or can provide insight.

Smoker specs:

CC - 16” dia, 48” long

FB – 16” dia, 18” long

 

Thanks.

 

[blacktopbutcher]

I've decided to go with 3" ID pipe for the chimney. It will likely be 30-36" in length above the CC. If I find that the draft is being an issue I can always remove some of the length if need be. I'm still wondering about where the exhaust should be situated on the CC though. I'm not sure how far down the opening should be from the top of the CC. the scetch below is what I would like some input on.  Any input would be welcome. From what I have seen a lot of people mod their stick burners with a sheet metal elbow inside the CC. I'm trying to address this mod now rather than fixing it later. Thanks!

IMG_1136.JPG

• blacktopbutcher
• Apr 7, 2015

 

[beuler]

I'm no collage grad, but looking at the pic, I'm imagining your big brisket laying on the rack plugging the hole to your stack....maybe put it up higher.

 

 

[scott s]

Keep reading and searching other guys builds you will find the answer you are looking for.

Unless you stuff a big butt directly into the hole you wont have any flow problems.

Chimney release height is personal preference it seems to have gotten lower in the last couple years.

I just did a build with it completely below the cooking grate.

good luck

Scott

 

[daveomak]

You can always put a choke plate on top of the stack to cut down on flow... they also act to close off the chimney during storage..

 

[blacktopbutcher]

Thanks for the input guys! I think I may raise it a bit so the lower portion of the plenum is at or just above the cooking grate height.