[arminiusreturns]

Since you seem to have some expertise in this area, I am going to use the opportunity to ask a bit of a diagonal question I've wondered for a while:

I've seen claims about increase in airflow from bladeless fan designs (I know it's a bit of misnomer, as the blades are just hidden) for home applications. Is there a reason bladeless designs haven't been used in the UAV realm? I assumed the claims were just marketing, or the weight increase offsets the effeciency, or something like that, but thought I would ask.

[leetcrew]

are you talking about ducted fans? if so I've wondered the same thing. here's a plausible answer: https://aviation.stackexchange.com/questions/36726/why-dont-....

[CraigJPerry]

Well out of my wheel house unfortunately but i do know that “air multiplier” marketing speak is called something like the coanda effect.

A Tom Stanton video with his coanda effect quadcopter https://m.youtube.com/watch?v=Irp_vnmUWZ4

[snovv_crash]

The ducting 'shadows' the blade during forward flight, massively reducing efficiency. During hover they can help though.