Wow - it took longer to read all thru this thread than it did to build a UDS.
After reading all the good info on UDS-es I decided I had to build one. I found a food grade barrel and burned it out, bought a 22" grill at WM and started in on the project.
I made up a charcoal basket that is 12"dia X 12" high and built an angle iron frame to give it 4" of clearance from the bottom of the barrel.
Now, I'm just getting started with smoking and such, so I had bought a SNP at WM - thought I could make it work for a smoker. After several cooks I got it working pretty well - never really right - and it used a LOT of fuel. I was getting ready to haul it into the shop and make some major mods. but having read all sorts of good things about the UDS design, I decided to build one first before modifying the SNP.
I have a BBQ Guru, so I only drilled one hole at the bottom of my UDS so the fan could blow in there, and drilled eight 5/8" holes in the top lid with no smoke stack of any kind.
Well, Thursday night I got home about 10pm and loaded the basket about 2/3rds full of Cowboy lump with a few Kingsford briquettes in there too, oiled up the barrel and set the Guru for about 235 degrees.
Would you believe that 18 hours later - I was just beginning to run out of fuel. AMAZING. The UDS held any temp I set on the guru just absolutely ROCK SOLID. I could raise the temp five degrees - come back hours later and the temp was right where it should be. Lower it five degrees - come back later and the temp was being held perfectly.
The SNP is going to have the firebox pulled off of it and I'll weld up the hole and it will be relegated to grilling. (( In the process of getting into smoking I have also rediscovered just how much better hamburgers and steaks are when cooked over real charcoal instead of propane. ))
Want to thank everyone here who did all the preliminary design worked, and got all the bugs worked out.
I have no anxiety about putting on a brisket before I leave for work and have a cooker/controller system that will absolutely hold the temp perfectly.
Now that I know it works, I'm going to build a stand with a table attached and get the barrel painted and looking good. After I get that done, I'll post some pictures.