Quote:
Originally Posted by Frank Lee
I don't understand the theory behind the proposal- how it would be better than just the rounded leading edge(s). It would be fun to see it tested though.
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Hi Frank, thanks for asking...
I have to be careful how I 'splain it, so as not to lauch into incorrectness...
There is "a lot" of data regarding slots and their effect on wings, and I only know enough to be very very dangerous if we were flying this thing
Roughly speaking, the underside of the canard's "rounded edge" captures a high pressure zone. This high pressure zone is gently and smoothly squeezed down to a rather sharp "nozzle", where the air velocity increases and pressure subsequently goes down. This small jet of air blows across the surface of the top of the box at its leading edge (where all of the aero trouble usually is), which in wing terms is far back on the top side of the wing.
The whole attempt is to provide extra lift (actually downth) to the air and to delay it from stalling. A simple small radius like 4" on a 90 degree turn stalls very easily and then has lots of drag. The 4" radius with slot (calling it a canard) may also stall very easily and then have lots of drag, but if successful, the 90 degree turn will stall less and later!
One unknown is the location of the canard. Testing would tell us if lifting it up so say a 2" gap is better (at a cost of a bigger windage). My money is on "keep the windage low, and let the little slot do what it can". Stuffing the slot closed with foam could be an interesting test as well! Just think of all the fun we can have!
For say box on a semi, I would expect the rounded edge (slotted or not slotted) should be 20" or even 30" radius to be right-sized. If the radius is large enough, the slot may not help at all? But 20"-30" is not a practical size for your pickup topper. In any case, the sharper the bend, the more we need lift-cheating devices like flaps and slots and other devilry!
Speak up you aeronautical experts, and kick me in the pants! Somebuddy throw this easy model into your software program, and compare with a simple radiused leading edge!
Otherwise, if you happen to have a square boxed do-hickey that goes down the road, I believe that tacking this ON will be easier than sawing the box DOWN, and might even work betterer? A-B-A-B KNOWS FOR SURE!