Again, wondering about some theory for a future design. My main priority will be reducing weight and increasing flight time - I suppose this is a pretty common goal.
I have read a number of time about how using coax designs (twin motors sharing same arm) reduces the efficiency of the motors considerably, but that the arrangment halves the number of arms required (reducing weight). My question is where the balance changes from favouring coax to not favouring coax. I imagine that for heavier arms, a coax arrangement might be more efficient, however we could reach a point with some lighter arms where halving the number would no longer offset the lost motor efficiency.
Does anyone have any numbers or examples? Can we conclude anything on this? Are there other factors that outweight the importance of this efficiency issue like complications with the system, flight, stability etc?