Permanent RF smoker question

[nick981]

Hey all,

  I just found this site about a week or so ago and just want to say that I've all ready learned a lot!

  I am about to start building a concrete block RF smoker( which which will have a decorative stone face surrounding it). Needless to say the FB and CC will be square in design. I've used the calculator and all seems pretty clear except for the stack. For my build it suggested for a 6" stack that it raises 17 inches. Here's what's getting me. The inside of the CC is going to be lined with 2.5 inch thick refractory brick(including the ceiling). After the brick at the ceiling there will be a 1.5 inch air gap followed by a 2.5 inch decorative concrete slab.  At this point I have 6.5 inches between the inside of the CC to the exterior of the smoker. Do I include this in my 17 inches that was suggested or do I not and just make my stack from the start of the exterior of the smoker going 17 inches up?

  One other question for you: as far as the stack goes, I'm thinking of not using a 6" pipe as I believe it will take away from my useable CC space. Anything wrong with me using thin steel, welding in a rectangle (about 3"x 18") and putting it in instead? The calculator wants a chimney volume 485.97 cu/in. Does the cubic inches come from that 17 inches sticking out of the smoker? Thanks for any help you can throw my way!

 

[rasimmo]

I don't think there is any measurements that have to be followed exactly. The calculator is a great guide to get you close. If your build design changes those numbers a little, it will still cook great.  The height of the stack would  work either way you descried it. It would be easier to cut some off than adding it back, so I would go with 17" above top. If it is cooling too much and you have moisture running back down the inside wall of the stack cut some off and try again.

A far as the shape of the stack, that is personal preference too. If you get the volume close to what a 6" pipe would have you will be fine. I would think that a rectangle would look better on a buid like this. Nothing else on it will be round so why does the stack have to be?

 

[nick981]

That's a good point! Thanks for the input. As far as the volume goes, the calculator is talking about the volume of those 17 inches correct? From what I've seen on here and other places there seems to be a difference of opinion on how low to bring the stack, so I can't imagine the volume of what is inside the CC to be included. What is the general opinion here as far as the length of the stack in the CC? I've seen writings of people who love it at the level of the grate, and some that even like slightly below. I saw photos from one gentleman that put an extension on his so that he can do both pork and fish(I don't know the advantage of a higher stack for fish but it sounds cool!). I appreciate you getting back to me.
 

 

[rasimmo]

I believe the 17" it calls for is outside the cook chamber. The length inside the CC is personal preference. Some say lower lets more smoke stay in the CC. I am making mine where I can make easy modifications to it later. I think I can use that to even out the cook temps from top to bottofm. I have no evidence of this yet. I will be going home tomorrow and hopefully have a fire in it by the weekend.

 

[nick981]

Rassimo, did you get to fire it up last weekend?  How did it work out for you?

 

[rasimmo]

Fired up Friday evening just to see some smoke. I ran it about 8 hrs yesterday. Smoking a pig today. I will try to post pics in my build thread of today's progress.