Do you think that there is advantage to having tall upright air intakes over a ball valves at the charcoal basket level other than having to bend over to make an adjustment. Common sense tell me that there would be a better air draw but I really don't know
Morning.... Draft is created by pressure differential.... If you have 2 holes, side by side, there is no pressure differential...
If one hole is 30" higher up on a tube from the 2nd hole, there is pressure differential.... Add in hot air inside the tube and cold air outside... a bigger pressure differential and DRAFT is created....
Natural draft is in danger from friction... A long tube used as an air intake, is a device that creates a lot of friction hampering the air flow greatly.... That long tube can also heat up any incoming air from radiated heat from the drum... also killing draft.....
The original UDS with air inlet valves at basket level, an air tight cooking chamber with exhaust holes at the top of the drum, is an almost perfect cooker... Consideration must be given to size of exhaust holes, placement and number.... Too small, or too few and draw is limited... Given air expands when heated, the exhaust holes must be greater in area than the inlet holes, or the air flow will be restricted... What's the perfect number ???? Enough so you can cook at 300-350 ish to get that chicken skin just right... Too few holes or too small, there will not be enough draft to cook properly...
I'm a fan of holes around the top of the sides of the drum.. with the bungs plugged... rebar can be inserted into those holes for hanging meats, when needed and providing even distribution of exhaust gasses for even heat....
Start with 8 each, 1/2" holes spaced around the top wall of the drum.. use a step drill.... add more if you feel it is necessary....