New vertical/horizontal smoker build: Please critique

[andrewpalmer71]

Building a hybrid reverse flow/offset smoker with combination vertical and horizontal cook chambers.Please comment on my numbers for both operations (RF and traditional offset), answer my questions, and be as critical as possible.  

The horizontal cook chamber is a 24" diameter 40" pipe. The vertical chamber is a 20" diameter 42" pipe. Both pipes are 1/4 inch steel. The 20" diameter tank will be mounted vertically on the left side of the smoker, and the firebox will be mounted on the right side.

The reverse flow operation will use only the 24" diameter horizontal tube. So, I will install dampers on the vertical tank to seal the vertical tube off when I am operating the rig in reverse flow.

The offset will use both the horizontal and vertical tank, thus dampers will be open.  

I have crunched the numbers for the traditional offset using Feldons BBQ Pit Calc. The combined CC size for both my tanks was slightly less than the size referenced in my calculations, but I wanted to err on the side of caution and make the firebox bigger than I needed rather than smaller. 

Please Copy and paste the following URL into your address bar to find my numbers; recalc. them and comment.   

http://feldoncentral.com/bbqcalcula...fi=6.5,6.5,0,41.47,0.98&fc=11.87,16.78,110.59]Link to BBQ Pit Calculator[/url]

** Important question for the traditional offset operation: What is the best way to maximize heat transfer between the horizontal and vertical cook chambers? I have seen some builds where the vertical pit is notched and welded onto the horizontal pit leaving an opening for heat transfer.

And, other builds where smaller tubes are welded into the side of the vertical tank, and connected to the horizontal tank. Is this the best option for my build since my horizontal tank is bigger than the vertical tank? ( I am considering cutting two 10" diameter holes into the vertical tank, welding in sections of 10 inch diameter pipe, and fitting these pipes into the side of the larger horizontal tank. Then, I would have two baffles, and better control over heat transfer.   

As for the reverse flow operation, I calculated the following numbers using this calculator: http://www.smokingmeatforums.com/a/reverse-flow-smoker-how-to-calculate-build-tutorial. 

Inside tank diameter: 23.5" x 40" length

Tank volume: 17349 cubic inches

Firebox-CC opening: 69 Sq. Inches

     Half moon shape dimensions: Radius: 11.75" ; Height: 5.2 Inches; RF Plate length: 19.51"

Area Under RF plate: 69 sq. Inches

Area @ end of RF plate: 69 squ. Inches

FB air inlets: 18 squ. inches

I understand that some calculations in my RF design, such as minimum firebox diameter, are cancelled out by the need to for larger dimensions when I operate my rig as a traditional offset. Therefore, my firebox will be 24 inches cubed.  

I envision this design for my smoker, except mine will have an additional stack for reverse flow capabilities. 

My smoker will look like this: 

I know this is all a lot to digest, but any and all help is greatly appreciated. 

Thanks!

 

[smokedstanley]

Why not just move the firebox under the vertical section and make it a full-time reverse flow?

 

[andrewpalmer71]

I am actually considering this option. I know Lang manufactures a reverse flow with a vertical smoking chamber situated above the firebox.

Can you give me some pros and cons of each option?

Also, any idea as to the size and design of the opening leading from the horizontal chamber to the vertical chamber?

 

[smokedstanley]

I built the one in my profile pic. It is a reverse flow horizontal to vertical cabinet. It worked awsome, sold it to build a bigger one. Either way you go I would not try for a hybrid. The baffle on a reverse flow works best when it is welded all the way(you don't want air leaks around the plate) and a traditional with tuning plates needs to be removable to clean under them and adjustments. 

The opening between the two chambers should be wide open in my opinion. I had mine half open and it screwed with the air flow. Once I cut it completely open the temps really evened out.