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-   -   Is the "chimney effect" just a myth? (http://www.bbq-brethren.com/forum/showthread.php?t=145339)

Heisenberger 10-03-2012 04:45 PM

Is the "chimney effect" just a myth?
 
Hello Brethren. I have a question about my UDS exhausts. Will threading the 8 holes in my lid with nipples create any chimney like effect (if that exists), or is it exactly the same as just having the holes bare. Does having a chimney actually "draw" the air/smoke out? Maybe this only happens if the chimney is a certain length.

I'm debating whether I should thread the holes with a pipe plug to close it off, or just install the nipples and use caps for cutoff...

CarolinaQue 10-03-2012 05:07 PM

I would plug thos 8 smaller holes off and put in a single 2 1/2" to 3" diameter X 12" long exhaust pipe.

Heisenberger 10-03-2012 05:12 PM

Quote:

Originally Posted by CarolinaQue (Post 2233713)
I would plug thos 8 smaller holes off and put in a single 2 1/2" to 3" diameter X 12" long exhaust pipe.

My original idea was to do this, however, I have a flat bung-less lid and my step drill only goes to 1-3/8'', which would make a hole fit for an even smaller pipe (maybe 1-1/4'').

landarc 10-03-2012 05:22 PM

I have seen UDS's that work fine with several small holes in a flat lid. Some that even just had pieces of steel or magnets to cover the holes. I agree that a larger chimney would work better. But, you have what you have. Go for it and see.

Smokin' D 10-03-2012 05:35 PM

I sometimes will slip a can over the exhaust on my WSM. Certainly seems to produce a better draw than without. Could be just my imagination though.

1MoreFord 10-03-2012 05:41 PM

Quote:

Originally Posted by Heisenberger (Post 2233707)
Hello Brethren. I have a question about my UDS exhausts. Will threading the 8 holes in my lid with nipples create any chimney like effect (if that exists), or is it exactly the same as just having the holes bare. Does having a chimney actually "draw" the air/smoke out? Maybe this only happens if the chimney is a certain length.

I'm debating whether I should thread the holes with a pipe plug to close it off, or just install the nipples and use caps for cutoff...

It's actually called stack effect and it is real.

You can read about it on Wikipedia. I'd drop a link but for some reason the forum won't let me. I keep getting an error:crazy:

Heisenberger 10-03-2012 05:42 PM

Ideally I would like to make a chimney, theres just no way for me to make a 2 inch hole without some outside help. I even thought of making 2 exhausts each 1-1/2''. I don't mind doing extra work or buying a few extra parts. I see this build as a weekend project and I would love to maximize its potential. Can't wait to try it out!

Smoking Westy 10-03-2012 09:20 PM

For my recent build I grabbed a 2 1/2" hole saw from Napa. It was fairly inexpensive and made quick work of the job. Added bonus is I now have the tool for future builds!

Not a typical UDS build by any means but you can see what I did...

http://i155.photobucket.com/albums/s...ng/null-11.jpg

Boshizzle 10-03-2012 09:33 PM

http://www.bbq-brethren.com/forum/pi...pictureid=2380

AustinKnight 10-03-2012 10:05 PM

I have what I think your talking about, and they work great for me most the time I only open 4 but to crank up the heat I'll open them all. I put them on cause of wind it helps with temperature control for me.Also keeps rain out and chokes out the fire fast using lump.http://img.tapatalk.com/d/12/10/04/he8ezedu.jpg

Sent from my SGH-T999 using Tapatalk 2

Johnny_Crunch 10-03-2012 10:05 PM

The 8 hole design with no nipples works fine. Don't over think this. KISS!

Harbormaster 10-04-2012 06:50 AM

Quote:

Originally Posted by Smokin' D (Post 2233737)
I sometimes will slip a can over the exhaust on my WSM. Certainly seems to produce a better draw than without. Could be just my imagination though.

A Bush's bean can with both ends removed fits snugly over the top vent tabs and has a noticeable affect on WSM performance in less than ideal weather conditions.

Terry Hesticles 10-04-2012 07:02 AM

I've only cooked twice on my week-old UDS, but I used the KISS method with 8 1/2" holes in a 15" diameter across the top of my flat lid. So far it's worked great and seems to offer plenty of exhaust, neither of my meals were ashy/sooty. In fact, despite calibrating my thermo, I've worried through both cooks that it was stuck because it held at the exact temp I wanted it to for the couple of hours I needed.

I also smoke on my patio with a large overhang so it's safe from precipitation. In furthering the KISS method, when it's time to choke the flame, I shut off my intake(s) and tear off small bits of aluminum foil to plug the holes. I do so in a manner similar to bits of toilet paper on your bleeding shaving nicks. Leaving the bits flat, I use my fingertip to settle them down somewhat into the holes and then I use my palm to flatten the foil around the holes. Simple and secure and within an hour or so my thermo reads ambient temps.

captndan 10-04-2012 07:21 AM

A steel pipe cap spells burned hands to me. How about a cork? Just an idea.

Smoking Westy 10-04-2012 08:27 AM

Quote:

Originally Posted by Harbormaster (Post 2234132)
A Bush's bean can with both ends removed fits snugly over the top vent tabs and has a noticeable affect on WSM performance in less than ideal weather conditions.



Good to know!


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