First time builder could use a little advice

Discussion in 'Reverse Flow' started by smokinsumbich, Jun 13, 2014.

  1. smokinsumbich

    smokinsumbich Newbie

    Hey guys, cool forum you've got here. I've got a few questions for the smoker gurus here before I start butchering good metal.

    I have obtained a water tank measuring 15 1/2" x 45" that I'll be using to build a reverse flow smoker. Would it be a good idea to trim the length down, or will a  45" cook chamber work fine with that small of a diameter? Is there some ratio I should stick close to here? It'll have a domed end at the reverse flow turn end, if that makes any difference.

    Today I picked up a piece of 1/4 plate for the firebox. I'm looking to build that square with a rounded top to fit the profile of a football shaped hole for my FB x CC transition. Good idea, or bad: Thoughts? Also, I can figure the size of the hole from Whatshisnames online pit calculator (times 1.5 of course), but I'm not sure how to transition that to the football shaped cutout. Help Plz.

    As for my reverse flow plate: Does it need to be thick, to act as thermal mass, or can I go with something thin, like 1/16" sheet to cut weight and cost? Is there an ideal thickness here? What about building double walled using thin stuff with an air gap? Anyone here do that before?

    Lastly, my chimney will most likely be relatively thick walled (1/4 +/-) round tube because that's what I've got at work. I can get 2, 2 1/2, 3, 3 1/2, or 4". What's my ideal diameter? The calculator just takes whatever I throw at it and gives me a length.

    Thanks in advance guys. I can't wait to upgrade from my crappy 12" char broil POS.
  2. I'll try to answer each question and if I miss one, it may be because I didn't understand it. Either someone else will answer or you can ask again anything missed.
    15.5" diameter you're only looking at getting one shelf in that size tank. I would vote to keep the 45" length as this will give you the room that you would otherwise be missing due to the smaller diameter.
    With the firebox I ALWAYS build the box width to match the tank diameter (just looks better IMO) then use the calculator and a little math to maximize your material/firebox size.
    With the RF plate I've used as thin as 3/16" but that was because the tank was that thickness. I wouldn't go any thinner because it is supposed to act as a thermal mass and create a convection effect and keep the heat more even throughout the cooker. Cheap out on that and you'll know it.
    I may find people who disagree but the RF plate ideal thickness is 1/4" any thicker is excess weight and ALOT more time to get up to temp, any thinner and it doesn't hold heat and can create a larger temp recovery window when you must open the smoker.
    The air gap is ideal in certain places within the smoker but not between 2 thinner pieces of metal acting as the RF plate.
    And lastly for the chimney I find it usually works out to use whatever diameter keeps the length of the chimney equal to or slightly longer than the diameter of the CC.
    I hope I've been able to answer your questions and am looking forward to seeing some pics of your tank and build, again if I missed anything ask again, there's plenty of us willing to spend your money .... uh ... I mean answer your questions. ;-)
    Last edited: Jun 13, 2014
  3. smokinsumbich

    smokinsumbich Newbie

    That was very helpful JW. Thank you.

    I don't usually post much DIY stuff on the internet, but I'll make an exception for this build. After all, this forum is where I learned about most of this stuff.
  4. smokinsumbich

    smokinsumbich Newbie

    The more I think about it, the domed firebox top is too much hassle. It's out. Besides, I was going to use cutoffs from the tank for that anyway, but there won't be any cutoffs.

    Running numbers this morning, I've arrived here:

    CC: 15.5 x 45"

    FB: 15.5 x 16 x 16" (I might make it a bit taller if metal optimization allows)

    Transition opening: 42sq In, half moon 4.25" tall

    FB openings: 6 x 2.5" rectangle main inlet, 1" round above fire w/ ball valve

    Chimney: 3.5" x 21" (probably protruding a couple inches into the CC, or off of a box on the end.

    How's it look? Any suggested changes? I'm especially concerned with the transition opening. The math calls for 35 sq Inch, but I oversized it a touch due to the long skinny shape of the CC. Did I oversize it enough? I can always cut bigger holes elsewhere, but this one needs to be right the first time.
  5. Here's what I would do, given the tank you have: Link to BBQ Pit Calculator

    I would not go much bigger than the 16" on the height and length, these measurements are already at 140% and give you ample room to add an ash clean out pan should you desire one. (I say DO IT) itS a common factor you'll find in all my builds only because I've seen to many people struggle to clean ash out during a cook due to their fire being suffocated.
    Also IMO only use the one style intake vent, you want to keep it as clean as possible so when you outgrow this one you'll have no problem selling it to fund your next build.
  6. smokinsumbich

    smokinsumbich Newbie

    Thanks, JW. That's good advice on the vents. I wasn't really thinking about aesthetics at all.

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