UDS Lid Vent Options

Discussion in 'Charcoal Smokers' started by hog warden, Jul 19, 2009.

  1. hog warden

    hog warden Smoking Fanatic

    In using my UDS, I have noticed how moist (wet) it runs, in relation to my older ECB or even a Weber kettle. Have played around with various vent configurations to see if that makes any difference.

    I'm using the removable lid, except my lid has two 2 inch bung holes,so yesterday, I tried it with two exhaust pipes. Left only one vent hole open on the bottom, and it was clamped down.

    With only one stack up, temp was running right at 225. After adding the second stack, I noticed only one was smoking. Looked closer and found the other was now drawing in air and after time, the temps started creeping up. I shut down the bottom vent completely and that only seemed to increase the draft from the top, with temps remaining up in the 250 to 275 range.

    Which got me to wondering, for those who used the 8 holes in the top configuration, do you have trouble keeping temps down or how does that work? Does it run wet or dry?

    As I recall, those are eight 1/2" holes, and if I'm doing the math right, each is roughly .2 square inches x 8 = 1.57 square inches of vent area.

    One 2 inch stack is right at 3 square inches or double the area.

    If anyone has tried both configurations, which works best?

    As I recall, a Weber kettle has 3 vents on the bottom and only one on top, which in terms of vent options, is exactly opposite of the way my UDS is setup.
  2. rw willy

    rw willy Smoking Fanatic OTBS Member

    When I was running the flat lid with the 8 holes, I noticed moisture.
    Now that I did the Weber mod I don't notice it. The big thing I think is the moisture runs down the sides of the UDS with the Weber lid. So, it doesn't matter at that point.
    Not sure if it is an exhaust problem or just because?
    P.S. temps were easier to hold with the original lid, due to sealing issues that need resolving with the mod.
  3. helljack6

    helljack6 Meat Mopper SMF Premier Member

    I use the bung on the supplied lid with a 6 inch pipe extension to help with draft pull. Leaving it completely wide open and one inlet pipe at full open and the ball valve set to 1/4 i hover right around 240ish. I'm using four 3/4 holes with 1/2x6 inch pipes threaded into them for air intake. I'm not sure what temperature i would hold at if I just used one intake, never tried it as I thought I'd be starving the fire if anything. Might have to try that next week after I get back.
  4. travcoman45

    travcoman45 Master of the Pit OTBS Member

    If we got much humidity tall, I get alot a moisture build up, reason I put in a drain. I just use the weber lid an leave the vents wide open, wind up with one cap on the intakes, one open an the valve I tweak ta hold 225° ta 250°. What seems ta work fer me. The moisture is just somthin ta live with I guess.
  5. billbo

    billbo Master of the Pit OTBS Member

    I have the eight x 1/2" set up and have moisture all the time. The UDS is a very moist cooking environment. I will someday be installing the Weber lid so we will have to see.

    I know DDave has had his set up both ways. Curious if he has any take on this.
  6. ddave

    ddave Master of the Pit OTBS Member SMF Premier Member

    Well, I've never used the 2" bung, but I have used the flat lid with 8 - 1/2" holes. I then drilled them out to 1" and finally went to the Weber lid.

    When I was using the 1/2" holes, temp control was not a problem. When I increased them to 1" temp seemed to get carried away if it was windy and the wind was blowing across the top of the drum. With the Weber lid, I have a pretty good fit and temp control is not that bad if I keep an eye on it and am careful when doing things with the lid off.

    As far as moisture goes, I think it's like Tip says -- it's just something to live with. Drums are fairly tight which enables them to burn long and stable. As far as moisture build up in the drum, that depends a little bit on what I've been cooking. If I do a couple of tri tips, there's not much in the drum bottom after. If I do 10 pounds of pork butt and 3 racks of BBs, there's quite a bit. [​IMG] The nice thing about the Weber lid is that the moiture tends to run to the side of the lid rather than dripping from the center of the lid which happens from time to time if the center of the flat lid is lower than the edges.

    As far as which one works best, I'd guess that it depends on which you prefer. They all work well. There are LOTS of folks who use just the 2" bung hole with great results.

    Like so many other things with this hobby, I think it boils down to what you prefer and what you get used to.[​IMG]

  7. hog warden

    hog warden Smoking Fanatic

    The moisture accumulation in the UDS is a puzzle to me. It shouldn't be any tighter than a Weber kettle unless it's from bigger pieces of meat. Moisture aside, the other thing I notice about them is how black everything inside gets. Sides and lid....yes, but the meat also get's blackened more than I would think. Some day I'm going to put some type of baffle plate over the charcoal basket to see if that changes things for the meat part.

    I'm currently doing a test burn......no meat on....so no moisture to test for.....but I have the lid on, am messing with blocking both bung holes, now and then cracking one a bit to vent it. All three air intakes on the bottom wide open. In short, damper is at the top vs at the bottom. I threw in some small twigs and sticks .....yard waste.... to generate smoke to see what is going on. Lid isn't "drum tight", so some smoke is venting from the lid rim. Seems to me like this mimics the normal Weber setup and others where the damper is on the top side of the smoker.

    Temp is holding right at 225, same as the normal setup. All blocked off, it runs slightly cooler...just above 200. Curious to see how long it burns, how complete the charcoal burn is......under normal setup I get several pieces at the end that just go out.

    If this pans out, I'll do a butt in a couple days for a better field test. What could go wrong with that plan? [​IMG]
  8. travcoman45

    travcoman45 Master of the Pit OTBS Member

    Ear-ache-my-eye tried a baffle on his an tossed it, but hey you might have a different idear, give it a whirl an let us know how it comes out.

    As fer the black, I get decent color on the inside a my drum, not really black more mollasses color, food usually ain't black, its a darker color then with the GOSM but that be because it's charcoal I thin.
  9. ddave

    ddave Master of the Pit OTBS Member SMF Premier Member

    Well, water vapor is a byproduct of combustion so if you're burning wood, or lump, you're bound to get some. Now whether there will be a build up in the drum without meat will most likely depend on humidity like Tip says. In the winter I notice more. When it's 110° with 15% humidiy (like it is today) I probably wouldn't get much moisture build up in the drum unless I was cooking some meat.

    As far as the black color in the drum goes, that's seasoning. As far as a darker color on the meat, that's probably caused by the somewhat more direct heat plus the reflective heat from the sides and top of the drum which help in cooking the meat. Things cook faster typically in the UDS in part due to this reflective heat transfer.

    Feel free to add a baffle. Many have tried and most have abandoned it. It makes the drum much less efficient. But some people don't like the flavor that the vaporizing fat imparts on the meat so they do use a baffle/drip plate.

    As far as experimenting with top vent/bottom vent and which ones to close, I'll think you'll find you'll get the best performance and tastiest meat by leaving the top vents wide open and using the bottom intakes to control the heat. The UDS is not a Weber kettle and is pretty simplistic in its design. It is simple efficient and effective. Doesn't get much better than that.[​IMG]

    If you're interested here is a thread that talks a lot about experimentation and contains a TON of posts from experienced UDS users describing their experimentation, tweaks, successes and failures with UDS design and use.


    It is currently 244 pages long but contains a wealth of information. I would call it "UDS Theory". [​IMG] It's a great read if you have the time.

  10. hog warden

    hog warden Smoking Fanatic

    Did some more field research yesterday. I live about 15 minutes from the Spice Wine folks and was driving by there yesterday, so dropped in for a visit:


    A UDS drum smoker has a remarkable similarity to the upright smokers these guys make, which are reputed to be some of the best in the business. Most of their stuff goes to competition smokers and they are excellent build quality.

    But in operation, interior volume is about the same. Sliding vent on the bottom.....2 inch vent stack on top with a gate value to control draft on top. Has racks elevated above the meat and charcoal pan on the bottom.

    Operation is to dump one chimney full of charcoal (with wood lumps) on the charcoal grate and that's it. Runs 225 for 3 to 4 hours on one chimney, at which time, you reload with charcoal only. Water/drip pan elevated right above the charcoal, forcing heat and smoke to the sides, so the cooking process is more convection (indirect) vs. the direct radiant heat you might get with a drum and no pan. They always add water to avoid grease fires and would never suggest smoking without the drip pan.

    Trial and error by users has found best vent option is about half open top and bottom. The inside blackens, but doesn't get "wet" as the drums seem to do. After the smoke, they open the vents to heat her up and burn out the grease to help with cleanup.

    So to mimic what their setup....... for the next smoke I'm going to add a 2 inch gate valve to the vent stack, and try to balance that with 2 full vents open at the bottom. I found from my test burn, I can block it on top with all three vents open on the bottom and still maintain 225 degrees for hours and hours. Will also add the drip pan from my ECB over the charcoal basket to move to indirect heat.

    Will report the results.
  11. hog warden

    hog warden Smoking Fanatic

    Well there are the results of my first research project!

    Babybacks. Two (bottom) had Blues Hog rub and sauce. For those with milder tastes, one with no rub and Shoe Me sauce (top). This was the tail end of 1 in the 3-2-1 method. Twenty minutes later they had been rendered to a pile of bones.

    Anyway, for this test burn, I put a tin can in the middle of the charcoal basket to cut down on the amount of charcoal and trying to get a more complete burn. Into the basket went about 1.5 x to 2x the amount of charcoal in a chimney, plus one full chimney of lump, minion method. Plus a few larger chunks of pecan and cherry on top.

    For this burn, I put my 30 gallon lid on TOP of the basket like a drip pan, so it was more of an indirect method of cooking. I started out with two full vents opened on the bottom, and on the lid, moderating with one 6 inch tall vent stack in one of the 2 inch bung holes, using the bung itself as a valve on top to open and close by sliding it back and forth over the hole.

    I found it an "iffy" method to regulate the temps, which started to spike up with that much air available from the intakes as the burn progressed. The idea was you could throttle it down from above (like closing the top vent on a weber kettle). That didn't work all that well. You would almost have to snuff it off completely at the top. I ended this smoke up by going back to the regular method of one vent open, 2 inch stack wide open and temps settled right down to 225.

    I think I do like the lid on top of the basket to isolate the meat from the coals. Based on the original concept of a drum smoker, the meat cooks by direct radiant heat as well as convection from indirect heat. It seems to me that without the lid, the meat is blacker (part bark but part something else......like something from the charcoal itself.....bitter stuff), that might be fine for a pork butt or brisket, but not something I care for on my ribs. With the lid in the middle, I didn't get any of that at all.

    Next up is a brisket. Full packer that is patiently waiting it's turn.
  12. ddave

    ddave Master of the Pit OTBS Member SMF Premier Member

    That seems to be the general consensus of the way the UDS likes to run.

    Some people don't like the flavor that the vaporizing fat imparts to the meat from the fat dripping into the coals. It could be some of the byproducts of the fat vaporization that you are noticing. Also, the flat lids tend to drip stuff on the meat at times which adds an off taste.

    But that picture speaks for itself. [​IMG] Damn nice looking ribs there for sure.


  13. hog warden

    hog warden Smoking Fanatic

    Latest research project.......yeah right....I just wanted some brisket. Anyway.....the test case.....a full packer from Sam's....rubbed and ready:

    Rubbed the night before. Full basket with some pecan chunks....a full chimney of lump and meat on at 6 AM. For this burn.....normal setup of the valved vent wide open.....full 2 inch stack up and open.....but I placed the drip pan from my ECB upside down over the charcoal basket to protect it from the drips (made a hell of a mess in the bottom.....but no grease fires). Temps held steady most of the day:

    It's like the thing is broken. It just doesn't budge....hour after hour.

    At 9 hours, temp had moved up to 150.....not what I wanted but dinner was supposed to be at 6. Executive decision time. Moved to a foil tray and covered and continued on another 3 hours. Rested one hour (do not answer the phone when you have BBQ to attend to). Devoured at the 13th hour.

    Thoughts on doing my first full packer? Next time, I'm going to separate the point and the flat up front. Do them separately together. I'll get rid of a lot of that fat. Leave some cap, but a lot of fat will be trimmed. Rub and smoke both about 3 hours.....then move both to uncovered foil trays. From there, they will stew in their own juice at the normal schedule. Putting them in the foil trays will eliminate all the fat and grease falling below, cleaner burn and cleaner drum, and the meat needs the liquid and fat anyway.

    The point has a lot of fat inside the muscle......between the muscle fibers. Those are going to stay juicy longer. By comparision, the flat doesn't have all that much, which may be why the seem to dry out more. Left in a tray, they may retain more of the natural juices without resorting to basting. And retain the low and slow through the whole smoke.

    Towards the end, I had to turn up the air some, but still had 200 degree plus temps at 12 hours.

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