Sharp rotor

Peter Sharp is the inventor of this rotor which uses both Magnus and Kramer effect. The experiments I do confirm the lift to drag ratio of 2, that is a low value in absolute terms, but a high value for a self-rotating device like the one based on Savonius design with a lift to drag ratio of 1.
Foam prototypes were realized by using a cnc cutting machine and the profile below:


as a possible rotating kite with ball bearings:

for gliding tests:


for gliding tests:

as a possible rotating kite:

The Magnus effect is also used by Omnidea, but a motor is implemented in order to rotate the balloon:

For the following some numbers are deduced from

By my experiments and measures (see the videos above) and also some data from the inventor Peter Sharp about the Sharp rotor, the coefficient of pull could be between 2.2 and 3.3, involving in an average power of roughly 0.37 kW/m² for 1), 0.5 kW/m² for 2), and 0.6 kW/m² for 3), using yoyo mode and a vertical trajectory far from the winch as described in the chapter 13 (see at the end of the page) of AWEbook 2018. The three sketches are below:
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During reel-out power phase it rotates. During reel-in phase it does not rotate, as for a Flettner rotor, but without spin motor.

Peter Sharp indicates that “A Sharp Rotor, due to its many curved surfaces, will be much stiffer than a cylinder”. So it could scale more than a Flettner-based balloon with the same holding by the two ends.

A solar balloon version would limit landing and take-off operations, without using helium.

As an inflatable version of the Sharp rotor would be highly scalable, as the unities within a farm could be close each other with low damages in the case of collisions, as the risk of collision is limited because the straight trajectory of each unity is easily manageable, the Sharp rotor could be an interesting AWE solution. Indeed the low efficiency per kite area is compensated by a better power/space use ratio.

By the experiments and some rough measures related above (coefficient of pull force at 12 m/s wind speed being 3.3, at 10 m/s wind speed being 3), and due to the huge power consumption of Flettner cylindrical balloons (which seems to be several times that of a rigid cylinder) as indicated on Scaling by size and on Scaling by size with a video, the Sharp rotor looks to be the more efficient device among Magnus effect-based balloons if the inflatable version keeps its features.