My first RF smoker build, any help would be appreciated

Discussion in 'Reverse Flow' started by jhsdigital, Apr 15, 2013.

    • jhsdigital,   I believe its not so much the heat from the fire box as it is the airflow coming into contact with the reverse flow plate the way it does that causes the hot spot. Any time the airflow has to take a turn, it will heat that area the same way a river will eat away the bank .
    What you want to do is get the air flowing horizontal BEFORE it comes in contact with the reverse flow plate, adding the deflector plate will do that, and the deflector plate will absorb the heat rather than the reverse flow plate.

    SQWIB'S is one way to do that, and there are several other ways. But as long as the air is going horizontal before it contacts the plate is all that matters.

    [​IMG]
     
  1. I like to add a second plate to the top, this works for me, but even just a little piece of plat bar welded in the opening deflecting the air down will work

    [​IMG].
     
  2. sqwib

    sqwib Smoking Guru OTBS Member

    Click on the pic below for my first test



    Here's a chart for my 2nd test  averaging about a 15 degree temperature variance.

    No it will not affect the flow. You only loose about an inch of head space.

    The top of the firebox does become insulated somewhat, think about a propane torch directed at a piece of metal, it will get red hot, now put another piece of steal behind that with an air gap and see how hot that plate gets. Its the only analogy I could come up with.

    My baffles get red hot, but the top of the firebox does not, it gets hot but not hot as before.

    • If you have proper draft the hot spots will be reduced. Note the flame getting sucked in under the RF plate.
    • I  don't cook like this, but wanted to show you how the heat would travel (same as the fire)
    • The hot spot used to be to the right, you can see where the firebox sits inside the smoke chamber, just like yours.
    I guess someone could run the RF plate completely across the top over top of the firebox

    • So far I have tried Charcoal, Lump, Propane, Hardwoods. all work well, the charcoal takes a bit longer to get frank up to my desired temp. The hammering effect is more prevalent with an actual flame, once youy are running on a good coal base, the hammering effect diminishes a bit.

    Since I added the baffles, I think I get about a 12° variance from left to right at my optimal smoking range, but as the temp goes higher so does the variance, but here's where it gets weird.

    The hot spot now becomes the coolest spot. I think it has to do with the draft increases dramatically.

    Below are pics I took when I done my Fast And Hot Ribs at around 450° - 475°
    • Left (open end of Reverse Flow Plate
    • Center
    • Right (Firebox side)

    Oh BTW the ribs were awesome.


    Hope this helps.
     
    Last edited: May 14, 2013

  3. OK, this is what Im thinking about doing. Any thoughts, comments or suggestions?

    A. The green lines represent my baffle plates

    B. The red line is my RF plate

    C. The yellow are my air intakes,

    The yellow line with the question mark is an additional air inlet on the FB door to help move along the heat (I think this is what you meant Dave) The pit calculator recommended four inlets, is it better to place all four on one side below the wood grate or two on opposite sides of the FB below the wood grate?
     
  4. SQWIB, Thanks, the propane analogy makes sense, also the pictures helped alot
     
     
  5. sqwib

    sqwib Smoking Guru OTBS Member

    To be honest, I wouldn't want to have that baffle hanging down, there may be a possibility of a swirling effect, I would want a smoother tapered transition into the firebox.

    I could be totally wrong but just wanted to point that out.

     

  6. SQWIB, I thought that if it angled down it would help in eliminating the hot spot. But never considered the possibility of a swirling effect. If I angled it upward at a slight angle would that be a better solution? Also what do you think about inlets on just one side of the FB or on both sides of the FB?
     
  7. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    The heat shield can be made of 1/8" or 3/16" ..... and an air gap of 1/4" or more should be sufficient...   all you are doing is breaking the path for heat transfer...  The heat shield can be suspended on bolts or welded in...  bolted, will allow for expansion and contraction...  leave a 1/4" gap on the 3 sides or however it fits in the FB and CC.... complete coverage is not necessary..  gaps at the edges is fine....    All you are trying to do is stop the blast of heat from the fire...    Make sense ???? I will draw a picture and send it to you ....   remind me in a PM....     Dave

    EDITED

    Below is what I had in my pea brain for an idea......

                            .....click to enlarge...........

     
    Last edited: May 14, 2013
  8. Did you put an air opening in the top of your firebox also to help the air move and add cool air to your flow?  I only put air vents in my firebox on the door side, but they are quite large enough to do the job.
     
  9. oops, how they work we will find out in the next week.
     
  10. Urbotrimmm, If you look at my colored diagram I'm thinking about placing an air inlet on the door to FB, Its where the yellow arrow and question mark are in the diagram. Hopefully this will allow air into the FB causing flow down the RF plate
     
     
  11. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    That is a great plan.....   Do It.......  
     
  12. Well I got the FB welded on, finally. Now it's on to build Dave's version of a heat baffle plate. Going to try and make it as one piece, like the bolt on idea, I think that way you can always remove it relatively easy for adjustments if necessary.  Thanks again for everyone's input and help this forum is amazing, thanks google.




     
  13. 05sprcrw

    05sprcrw Smoking Fanatic

    Making some good progress!
     
  14. sqwib

    sqwib Smoking Guru OTBS Member

    MAN this brings back memories, looking good.
     
  15. Any thoughts of adding firebrick to the bottom?
    Looks good!
     
  16. If you aren't going to insulate the bottom then I would deffinately add bricks especially if you are keeping this smoker.  Just my opinion.  Nice looking build so far.  weld on my man
     
  17. urbotrimmm, I was going to put a pullout fire grate just above my air inlets. This would put the grate about 4.5 inches above the bottom of the FB. Would the bricks be for insulation only? keeping the heat in the box or would they be for wear on the bottom of the FB? Sorry, if it seems like a dumb question, just haven't seen any bricks in other smokers I have looked at prior to starting my build. I really want this thing to turn out a good as I can get it to.
     
  18. The bricks should both insulate and save your floor from burn through. They'll warm up and help stabilize your temps as well, especially after everything is good and warmed up.
     
  19. What he said to the T
     

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