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View Full Version : Hello, and my first BBQ (UDS, of course), and vent questions


MTScott
11-25-2013, 04:16 PM
So, howdy... I'm just getting into BBQ and this seemed the place to register.

I have a few friends who BBQ with electric and gas, and I have had too much great pulled pork and brisket at their homes to resist doing it myself. So, I've embarked one what surely will be my next addiction as a hobby (like I need any more).

After doing some research, it seemed that a homemade UDS was a proper way to start. I wish I had more build pics along the way to show you, but this is all I have:

http://i82.photobucket.com/albums/j274/Lambo3MT/BBQ/IMG_20131109_141053_013_zps6715b03c.jpg (http://s82.photobucket.com/user/Lambo3MT/media/BBQ/IMG_20131109_141053_013_zps6715b03c.jpg.html)

http://i82.photobucket.com/albums/j274/Lambo3MT/BBQ/IMG_20131110_150809_574_zps151d24cc.jpg (http://s82.photobucket.com/user/Lambo3MT/media/BBQ/IMG_20131110_150809_574_zps151d24cc.jpg.html)

So far, i'm pretty happy with it. I experimented with a meat loaf, and a few other things that are kind of failsafe. And had success with a 10 lb boston butt. I did run out of heat/fuel around 12 hours though, and had to finish it in the stove - which worked out fine, but I'd prefer to finish it in the Q, as the stove heat management seems to have about a 75* range. Funny thing was there was still some fuel left (mostly very large hunks of lump).

So, this brings me to my questions. I located my vents almost right on the bottom (4 3/4" vents). This drum happens to have ribs that start about 1" off the bottom, and I was trying to avoid those so I'd get a cleaner seal.

Most seem to put their vents 2" off the bottom, and I think I know why now - so the air drafted in will blow more directly on the fire basket. I also have a 13.5" fire basket, so the combustion is a good distance from the vent.

I seem to have to run 2 vents wide open to maintain BBQ temps and sometimes that isn't enough. I find myself opening up a third often to get the temp up, only to have it drop back down to 200 when I close it. This seems like more air flow that most need??

I have a feeling some of the precious O2 coming isn't making it to the fire for combustion, but is rather going straight up the sides of the smoker. I was think I would make some sort of extension to attach to the front vents that uses 45s to raise the air vent up and extend it closer to the basket, this way the air drafted in will be aimed directly on the charcoal basket.

Any thoughts... ?? Am I perhaps over thinking this?

SmittyJonz
11-25-2013, 04:30 PM
Those 90* elbows really restrict air flow( as much as 50%) so most use 1" when using risers - I have 4 3/4" vents (no elbows) 2-3" off bottom and like to Smoke 275-300* so I will have all 4 open......1" off the bottom ash could block air. My basket is 18-19" Diameter. Cooking at 275-300* I never have to go past 10 hrs cook time and usually 6-8 hrs. Always run exhaust full open.
Does your basket sit 3-4" off bottom so ash can fall and air circulate under and up thru basket?

Bludawg
11-25-2013, 04:41 PM
JM2C remove one if the risers and put a cap in its place. I have 3 intakes on mine all 3/4" 2 nipples and one 12" riser with a ball valve I can run at 400 no problem wide open. Every bend you put in a line will restrict the flow by 50% so those 2 intakes that you have on risers are only as efficient as 2 3/8" nipples or wide open the same a 1 3/4" intake providing your valves a re full flow ball valves.

MTScott
11-25-2013, 04:53 PM
Those 90* elbows really restrict air flow( as much as 50%) so most use 1" when using risers - I have 4 3/4" vents (no elbows) 2-3" off bottom and like to Smoke 275-300* so I will have all 4 open......1" off the bottom ash could block air. My basket is 18-19" Diameter. Cooking at 275-300* I never have to go past 10 hrs cook time and usually 6-8 hrs. Always run exhaust full open.
Does your basket sit 3-4" off bottom so ash can fall and air circulate under and up thru basket?

Yeah... I don't seem to get as much response out of the risers, and that's unfortunate... I'm not sure I can upgrade to 1" now with out using a new barrel.

My basket starts with a basic 15" pizza pan, three bolts with spacers hold the basket about 1.5" off the pan. The basket is expanded steel welded around a 13.5" weber charcoal grate. All of the ash seems to collect in the pizza pan. My first step might be to space the basket another 1/2" up from the pizza pan. it is very possible that as it fills up with ash it is slowing air flow.

SmittyJonz
11-25-2013, 04:57 PM
Yup get about 3" clearance under the basket. I'd just ditch the risers and elbows and use the ball valves on pipe nipples.

MTScott
11-25-2013, 04:57 PM
JM2C remove one if the risers and put a cap in its place. I have 3 intakes on mine all 3/4" 2 nipples and one 12" riser with a ball valve I can run at 400 no problem wide open. Every bend you put in a line will restrict the flow by 50% so those 2 intakes that you have on risers are only as efficient as 2 3/8" nipples or wide open the same a 1 3/4" intake providing your valves a re full flow ball valves.

They are full port ball valves.

I do have two more uncapped vents to work with. I actually have run 400+ (I did to season it, and baked a pizza once). Wide open on all 4 vents and I can get some serious heat, but I did start with at least a half full chimney of charcoal. Running that hot I think the draft is strong enough to make it happen. It's when I try to slow it down that seems to be when it struggles.

SmittyJonz
11-25-2013, 05:05 PM
Also every UDS will run a little different cuz everyone is built a lil different plus amount and kind, brand and age of charcoal plus how much lit you drop in will determine how it wants to run . You can make good BBQ at 225* to 325* and all temps in between. If your UDS likes to run at 270* don't try to make it run 225* or 250*- it'll just frustrate ya. :wink:

T&S BBQ
11-25-2013, 05:12 PM
Why not change to 1" pipe. Get a unibit and drill a 1-3/8" hole and change to 1" pipe.
P.S. nice job on your build

MTScott
11-26-2013, 01:38 PM
Why not change to 1" pipe. Get a unibit and drill a 1-3/8" hole and change to 1" pipe.
P.S. nice job on your build

That's a good idea, but the 3/4" nipples are already right on the bottom, I'd have to some how drill "up" only, rather than rounding it out bigger.

I did fire it up last night and got reasonable results though. I cleaned it up and put about half a weber chimney on top of about a full chimney of unlit. I ran open for about 20 minutes, then closed off the back vents and left the two front valves wide open. I locked in around 250-275 (non diffuser, 4" thermometer probe). So, maybe I'm fine. My previous tests were very cold and breezy (single digit weather), so maybe that was throwing me off more than anything.

I will probably add a BBQ GURU to this eventually in which case none of this will matter much. I just figured I should learn the ropes with natural draft first.

P.S. Thanks, it turned out better than I figured it would. I did put a lot of effort into sand blasting (getting the inside was terrible), then painted it with an HVLP gun and some Rustoleum satin finish grill paint. Thumbs up for this paint, it went on well, looks good, and is holding up well.

Fwismoker
11-26-2013, 02:42 PM
Welcome to the drum club! Add what ever air you need to to achieve 400* temps if you need it especially for those cold Montana winters.

I cook poultry @ 350 and butts @ 275 so if it's cold out and i want 350* i'll open her up. You have to keep in mind climate because you and i will need more air than say a Texas guy in a warmer climate to get the same temps. Good luck and holler if you need anything.