I remember reading about vortices somewhere awhile ago, and about they can sometimes improve the air flow and thus also improve thrust, stability, quiet flight, etc.
I noticed that a majority of the Quad's and multirotors have the booms (the arms that hold the motors to the fram) go to the motor and not any further.
Now, I'm no aeronauticle engineer, but I think it would be possible to induce vortices by extending the boom up to the tip of the propellors.
Additionally, this might even make it easier on the motor because the force load on the blade would be more even when the blade tips go over the boom.
Ok... think of the propellor as being very flexible and like a sheet of paper. If you apply a force to it, it will bend to react to the force. When the propellor is spinning over the open air, the force is pretty consistant and thus the load is consisitant.
However, when the propellor spins over a the boom, the pressure is higher on the blade, because the boom is within 2 diameters of the blade. This ends up with the blade flexing and pushing against the axle of the motor (at least so I think).
Has anyone considered this before? If so, what where your conclusions?