I have a question about the efficiency of drives in multicopters.
I know that in general, the larger the propeller, the greater the efficiency.
Now there are coax designs that allow large propellers, but have the disadvantage that the lower one is downstream of the upper one and thus loses some efficiency.
What happens if you take a "normal" hexa/octo/etc copter and arrange the arms slightly offset in height. So that the propeller surface overlaps slightly at the edge.
Does this lead to vibrations/instability or is there some other reason this is not commonly done?
I thought of something like this:
I know that in general, the larger the propeller, the greater the efficiency.
Now there are coax designs that allow large propellers, but have the disadvantage that the lower one is downstream of the upper one and thus loses some efficiency.
What happens if you take a "normal" hexa/octo/etc copter and arrange the arms slightly offset in height. So that the propeller surface overlaps slightly at the edge.
Does this lead to vibrations/instability or is there some other reason this is not commonly done?
I thought of something like this:
, I've already built a few. 
