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View Full Version : Smokestack on a UDS


geniz
10-23-2011, 12:23 PM
Brethren,

I recently put a 1.5 ft smokestack on my UDS.
Previously I just had taken the bung out of the lid which opens up a 2" hole for the smoke to escape. Everything worked fine with the UDS. (Standard 55 gallon UDS with three 3/4" intakes, two capped, one ball valve, etc, etc)

Now with the smokestack in place, I really have to choke down on the intakes to keep the cooking temps in the 225-250 degree range. In fact today I had to partially cover the top of the smokestack when my temps overshot 250.

I've searched and haven't seen anyone else mention this

Am I crazy or have others experienced the same thing??

woodbutcher1
10-23-2011, 01:18 PM
The taller (longer.higher) the smoke stack the more draft ,therefore higher heat.

smokeyw
10-23-2011, 01:42 PM
^^^^^ What he said. Longer chimney means increased draft and hotter temps.

geniz
10-23-2011, 02:04 PM
Ok. Thanks. I'll either learn to cook on it ( looks cool ) or shorten it.

Glad I'm not crazy. ;-)

NorthwestBBQ
10-23-2011, 02:28 PM
The heat is controlled by the air intakes below. However, you may want to partially (25%) cover the stack. On large offsets this is standard practice.

Sammy_Shuford
10-23-2011, 02:36 PM
With the increased draft, air leaks will be more predominant with the intakes almost closed.

JMSetzler
10-23-2011, 04:01 PM
I'd like to have a 1 1/2' stack but I bought a 1' stack instead... My drum doesn't like to cook as hot as I'd like it to in many cases so I'm thinking about adding another air intake or two at the bottom so 400° will be a little easier to achieve.

joegiggles
12-27-2011, 08:10 AM
I noticed the same thing this weekend. I built a similar UDS in the fall and had no trouble holding 225-250. When the mother in law wanted a turkey for christmas dinner, I was afraid of the 30 degree temps would not let the smoker get hot enough. I wrapped a 4x6 welding blanket around the UDS and put a 1 foot stack on it to let it vent over the blanket. I couldn't figure out why I was running 100 degrees hotter than usual. I chalked it up to the blanket, but according to the thread, it was the stack as well...good to know

ssbbqguy
12-27-2011, 09:06 AM
It's more than just the stack length. It will have more to do with obstructions or methods of slowing down the airflow, as is my smokers which use a 3.5"diameter, long flue for an exhaust. There are many more factors than just one. Thermal efficiency is crucial,if use use a barrier or baffle, water pan, rack configuration and so on. When you can smoke cheese and make pizzas with all the temps in the middle of 140 and 425, without over smoking due to improper burn, then you have it figured out. Steve.