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Thread: Oil Tank Arch - Smokebox or not?

  1. #1
    Join Date
    Apr 2022
    Location
    SE Wisconsin
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    2

    Default Oil Tank Arch - Smokebox or not?

    I'm building an evap for a 2x4 divided pan using an old fuel oil tank. It appears that most builds have a "smokebox" at the back of the unit that the stack sits atop (the the mailbox-shaped part that you don't cut off the top of the tank when making the pan table). Is there a thermodynamic benefit to this? Seems it would be easier to cut the top flush off and have a flat area behind the pan that the stack is mounted on - then there's a bit of flat surface that can be used as a warming table.

    Thoughts on this are appreciated!

    I'm sure you all know what I'm talking about, but just in case the first pic is with smokebox, second without:



  2. #2
    Join Date
    Apr 2019
    Location
    Nashville, MI
    Posts
    753

    Default

    I have seen them done both ways, I don't know that there is an advantage/disadvantage either way. The one I inherited was flat and I used it to warm sap in metal coffee cans. that was my very first evaporator. 1 big square pan.
    2004 - 2012 2x3 flat pan 25 to 60 taps
    2012 2x3 new divided pan w/draw off 55 taps
    2018 - didn't boil surgery - bought new evaporator
    2019 new SML 2x4 raised flue high output evap. 65 taps
    made 17 gal. syrup
    2020 - only put out 53 taps - made 16.25 ga.l syrup
    2021 - Didn't work out
    2022 - 25 taps on bags / 8 taps on 3/16's line - late start

  3. #3
    Join Date
    Jan 2011
    Location
    Southern Ohio
    Posts
    1,289

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    I am in agreement with Pdiamond, I don't know if it matters. However, lining it with ceramic blanket behind the bricks will make a big difference. If you hadn't planned on ceramic blanket, I recommend it.
    125-150 taps
    Smokey Lakes Full pint Hybrid pan
    Modified half pint arch
    Air over fire
    All 3/16 tubing
    Southern Ohio

  4. #4
    Join Date
    Feb 2012
    Location
    Fond du Lac, Wisconsin
    Posts
    1,043

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    It is called the stack base. It's purpose is to allow the heat and smoke to evenly travel under the pan. If you just have the hole in the middle the heat will short-circuit to the center and the back corners will not get any heat. You can put a brick or some other blockage right in front of where the stack goes out to force the heat to the outside if you do not have a base but is not as efficient.
    Smoky Lake 2x6 dropflu pans and hoods on homemade arch
    Smoky Lake 6 gallon water jacked bottler
    Concentric Exhaust
    250 Deer Run RO
    325 taps

  5. #5
    Join Date
    Apr 2014
    Location
    Wakefield,New Hampshire
    Posts
    477

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    Super sapper said it. The mailbox style in the photo will help spread out the flames/heat to the bottom of the pan evenly not just the direct line to the smoke stack. Having that extra height over the other photo with the flat top will likely help create a stronger draft.
    6th season solo sugar maker in a young sugar bush of mostly red maples
    320 taps
    2x6 self built arch, Flat pans w/ dividers
    New 12x16 sugar house
    CDL hobby 250 RO

  6. #6
    Join Date
    Apr 2022
    Location
    SE Wisconsin
    Posts
    2

    Default

    Thanks Super Sap! This is exactly what I was looking for and it makes complete sense.

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