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Help on my First reverse flow smoker build

Discussion in 'Reverse Flow' started by marcoc, May 17, 2018.

  1. marcoc

    marcoc Newbie

    Hello everyone, I have been doing my calculations with the feldon bbq pit calc and wanted to make sure that I have done everything correctly.
    I have a cylindrical cook chamber 43.3"x15.5" with a cylindrical firebox 15.7"x15.5"
    This gives me a recommended throat opening of 23.7sq in
    If my calculations are correct the cut-out height that connects the firebox to the cook chamber should be 6.7".
    Since that will also be the height of the baffle plate I will have only 1" left from the widest part of the cook chamber. I have read that the baffle plate should be at least 2-4" from the cooking grate so I would have to move the cooking grate up a bit sacrificing some cooking area.
    Are my calculations correct?
    Any help is greatly appreciated
    Thanks in advance.
     
  2. SmokinAl

    SmokinAl Smoking Guru Staff Member Moderator OTBS Member ★ Lifetime Premier ★

  3. marcoc

    marcoc Newbie

    thanks for the replies. double checked all my calculations and now they are correct.
    one question.. what would be the best way to remove rust from the smoker?
     
  4. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Look at the tutorial SmokinAl had noted..... this would be the design for your smoker... Feldon's has some serious flaws for an excellent operating smoker...


    8170 c. i. CC.. 32.7 sq. in. FB/CC opening ....
    15.5r x 43.3 CC 1.jpg
     
  5. jbellard

    jbellard Smoking Fanatic

    Listen to Dave! He has helped a ton of folks design their smokers correctly.
     
  6. weedeater

    weedeater Smoking Fanatic ★ Lifetime Premier ★

    Dave will not lead you wrong! Go slow with your build. Plan it all out. Post lots of pics as you go. Ask questions, get input, plan, plan, plan. Above all else have fun!

    To your question about the rust—- you can remove the loose stuff with a wire brush, sander, flap disk, etc. burni it out at some point will also help. “Ospho” is a product you can apply that will make the rust disappear. You can find it at Ace Hardware stores by the gallon and probably at other stores. I don’t really understand how it works but is great stuff to apply before painting.

    Weedeater
     
  7. marcoc

    marcoc Newbie

    Thanks for your help Dave. Got the same numbers you have after long calculations! I must have made some mistakes making conversions from inches to centimeters as that is what i'm used to. I've scratched all the feldon calculations. IMG-20180526-WA0001.jpeg
    I've started today on the build. Starting from a 236" pipe and will make 3 smokers out of it.
    Looking forward to keeping you updated!
     
    Last edited: May 26, 2018
  8. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Cool.... We love pictures.... especially when finished and the meats are on the rack, then the plate...
     
  9. marcoc

    marcoc Newbie

    Hello Dave,
    just wanted to ask why the rf plate height doesn't match the fb to cc opening height. Is that to have the ideal distance from the cooking grate?
    Going to cut the doors this week. Should i make it 1/4 of the circumference?
     
  10. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Are you asking why the RF plate is 4.75" from the bottom and the opening is 4.5" high ????

    just wanted to ask why the rf plate height doesn't match the fb to cc opening height.
     
  11. marcoc

    marcoc Newbie

    yes
     
  12. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    1/4" is not a big deal.....
     
  13. marcoc

    marcoc Newbie

    Another question... I've read that you should keep the area of the rf plate opening at the opposite end of the cook chamber the same size as the firebox to cook chamber opening. with a RF plate 13.6" wide, should I have an opening of 2.4"?
    Thanks
     
  14. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Considering the air flow has to take a 180 deg. change in direction... That will cause a flow restriction... It would not hurt and be a plus if the opening at the end of the RF plate was larger... I would open up that opening, as much as possible, without sacrificing other aspects of the cooker..
     
  15. marcoc

    marcoc Newbie

    Hello, been working on the smoker a bit slower than I was hoping for. I was looking at the calculation for the smoke stack. If I understood correctly you suggest a stack length of 36" and adjust the diameter to get the correct volume. With a CC of 8170 c.i. I calculated an exhaust stack volume of 180 c.i(8170 * 0.022). With a smoke stack length of 36" and 180 ESV I get a pipe diameter of 2.5". Is that pipe diameter large enough to grant a good airflow?
    Thank you. IMG-20180710-WA0004.jpeg
     
  16. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    NO.... In a small smoker, small parts etc, the friction from small diameter pipes etc., increases the surface area to volume ratio... screwing up the air flow... Go big... I'd use 4" at about 32-36".....
     
  17. marcoc

    marcoc Newbie

    Hello again! the build is close to being ready, thanks for your help. I was thinking about the design of the smoke stack and made a drawing, hope it's clear enough. IMG_20180807_012756.jpg
    I would cut the top of the cook chamber down to the cooking grate (shaded area) and then weld the smoke stack to it.
    Is this a good idea to have a good airflow with no friction? Am I cutting out too much steel from the cook chamber?