My first RF smoker build

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Original poster
Feb 17, 2016
Melbourne, Victoria, Australia
Hi all
So I'm attempting a smoker build and to say I'm not totally grasping the maths behind it would be an understatement.
The tank I'm using has an overall length of 33inches and a diameter of 18.5inches, if my math is correct it would be about 33 gallons and that's with allowing less volume because of the end tanks. Is this to small to make a smoker out of?

I was thinking of starting with the FB/CC half moon opening first so I could work out door placement from there. I've put in a FB dimension in Feldon's bbq calculator and it's given me a half moon opening size of 7.2 inches, now I might sound stupid here haha but do I mark a line from edge to edge that's 7.2inches long? Like this

Would anyone have an opinion of what FB dimensions I should use?

Any help would be greatly appreciated
Thanks in advance
So I haven't been on here for awhile, had stuff going on. Anyway I'm slowly getting along with my build and need some advice on my firebox intakes. I've marked on the box where I'm thinking of putting the door and intakes but started think having all the intakes under the fire level might not be a great idea. Here's some pics Any help or opinion would be greatly appreciated
Cheers guys
Well 3.5 is better than 4.5 haha. I don't know how I missed by so much. I know it's not on you to work everything out for newbies on their builds but that 3.5 is spot on? Thanks so much I really appreciate it. You've saved me a lot of heartache and anger haha
My apologies, I didn't fully grasp it before but now I understand it(I hope)

The calculator gave me a FB-CC opening of 23.40

And this is what I got from the segment calculator

Then I'm assuming I add 1/4inch on top of that for the thickness of the firebox

Am I in the ball park?

Again I'm sorry for being annoying but I do appreciate the help you're giving me

Last edited:
You've got it......  NOW, using Feldon's numbers is NOT the way I would go....   Use my calculations....   Feldon's will cause you an overheated Firebox and poor heat/smoke flows through the smoker....   Have you opened that link and read it ???

Your CC volume X 0.004 will  be the area between the FB and CC....   area under the RF plate and area at the end of the RF plate...  

Diam. 18.5 X 33" length....   18.5 x 18.5 X .7854 X 33 = 8870 cu. in. X 0.004 = 35 sq. in. FB/CC opening

Using the circle calculator, click on radius and segment height box...   put 9" in radius box....  3.5" in segment height box....  

NOW...   ED is the height of the cut.....   AB is the width of the cut...   ED is how high from the bottom of the CC is where the RF plate goes...   ED is how far from the end of the CC is where the RF p[late ends....

8870 CC volume X 0.022 = 195 cu. in for the exhaust

195 / .7854 X 3 x 3 = 27" high stack BUT I would use a 3" exhaust stack 34" tall....

I'm just trying to help you understand where the numbers come from....   read the tutorial I have put together...  It explains a bunch...  Once you understand why I built a new tutorial and promote it over Feldon's, this krap should make sense....
That's a relief, thanks for that.
I'll run through those calculations you gave me tomorrow after a good sleep.
Yep I did open it up and have a read, I think somewhere in that thread or maybe another one you made a post about hoods bending when cutting out. I was cutting out mine and it started bending out so I stopped and welded it back down. Any tips on stopping it doing that?
 Any tips on stopping it doing that?

Not that I know of...  It's from stress during the rolling process...   Maybe, install the FB and exhaust, and build a really hot fire to relieve the stress in the CC tank.....  don't know really...... is reader supported and as an Amazon Associate, we may earn commissions from qualifying purchases.

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