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smith54
Joined: 14 Aug 2011
Posts: 18
Location: chicago,il
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 Posted: Sep 01 2011 Post subject: STACK SIZE / ? |
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I have used the calc for my chimney size but am unclear of a couple of things.I have obtained 16 ft of 4 " x 3/8" wall pipe.This actually measures approx 4.5" o.d. and approx 3 7/8" i.d. Does the calc use i.d. or o.d.? I plan on putting 2 side stacks at the main grate height on each side. (i have decided to make this a hybrid unit). my firebox is 20" round by 24"L.I want this to draw properly, but not sure of the math when you have 2 stacks? i figure the max height i could fabricate ,given my material would be about 38".Any opinions /comments would be appreciated. (offset 24" x 48")
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k.a.m.
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Joined: 12 Dec 2007
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Location: Southeast Texas.
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| Posted: Sep 01 2011 Post subject: |
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smith54, the calculator uses ID measurements. As far as the length using two stacks. If the calculator measures out a single stack 40" long then two stacks at 20" would equate to the required volume. I hope this helps. 
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smith54
Joined: 14 Aug 2011
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Location: chicago,il
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| Posted: Sep 01 2011 Post subject: |
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Thanks KAM. I am an hvac tech by trade and the 20" height just made me nervous. Something in my head says its too short to draft properly. Then again its not a masonry furnace chimney either.
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k.a.m.
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| Posted: Sep 01 2011 Post subject: |
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smith54, if you feeling unsure on the two 20" I think you could bump them to 30" tall. You could use dampers on the top if you need to slow your draw some and the dampers will keep the weather and critters out when not in use.
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the420Angler
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Joined: 11 Jul 2011
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Location: Barrie, ON
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| Posted: Sep 01 2011 Post subject: |
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this sounds like the same situation I have at the moment. The calculator says mine should be about 36". I had planned to have them both at 36" and have one or the other completely closed most of the time and then half open if I was going to use both stack together. Will this cause me trouble?
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k.a.m.
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Joined: 12 Dec 2007
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Location: Southeast Texas.
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| Posted: Sep 01 2011 Post subject: |
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| the420Angler wrote: | | this sounds like the same situation I have at the moment. The calculator says mine should be about 36". I had planned to have them both at 36" and have one or the other completely closed most of the time and then half open if I was going to use both stack together. Will this cause me trouble? |
Keeping the second stack closed most of the time should not be a problem. I doubt the second stack will see much service. The problem with more draft than needed is your heat/smoke exchanges in the cooking chamber to quickly for effective smoking. You can also create a severe hot spot at the firebox side because your pulling the hot air in stronger.These things I have found out through trials an errors on my back yard cooker just playing around with stack sizes and placements.
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smith54
Joined: 14 Aug 2011
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Location: chicago,il
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| Posted: Sep 01 2011 Post subject: |
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I've read that if you close your stack damper too much you can create creosote on your smoker and the meat?
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the420Angler
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| Posted: Sep 01 2011 Post subject: |
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okay thanks Kevin, great info as always.
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k.a.m.
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| Posted: Sep 01 2011 Post subject: |
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| smith54 wrote: | | I've read that if you close your stack damper too much you can create creosote on your smoker and the meat? |
Your correct in some ways. If the cooker is designed to run with the dampers wide open and you try to control your temps with them then your slowing a proper draft and will create a stall and creosote will form. But if you design your cooker with an over sized stack as some do you can after practice control the draft with your damper to create the proper draw for the day at hand.
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crb478
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Joined: 06 Dec 2010
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| Posted: Sep 01 2011 Post subject: |
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| k.a.m. wrote: | | smith54 wrote: | | I've read that if you close your stack damper too much you can create creosote on your smoker and the meat? |
Your correct in some ways. If the cooker is designed to run with the dampers wide open and you try to control your temps with them then your slowing a proper draft and will create a stall and creosote will form. But if you design your cooker with an over sized stack as some do you can after practice control the draft with your damper to create the proper draw for the day at hand. |
Thanks KAM you have just answered my question for me as to why I have to close my damper slightly on my cooker to keep the temps close to even end to end when everyone else seemed to keep their exhaust wide open. You have a wealth of knowledge about cookers. |
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k.a.m.
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Joined: 12 Dec 2007
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Location: Southeast Texas.
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| Posted: Sep 01 2011 Post subject: |
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| crb478 wrote: | | k.a.m. wrote: | | smith54 wrote: | | I've read that if you close your stack damper too much you can create creosote on your smoker and the meat? |
Your correct in some ways. If the cooker is designed to run with the dampers wide open and you try to control your temps with them then your slowing a proper draft and will create a stall and creosote will form. But if you design your cooker with an over sized stack as some do you can after practice control the draft with your damper to create the proper draw for the day at hand. |
Thanks KAM you have just answered my question for me as to why I have to close my damper slightly on my cooker to keep the temps close to even end to end when everyone else seemed to keep their exhaust wide open. You have a wealth of knowledge about cookers. |
Thank You and your very welcome. 
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