Crab
To Crab,
To funny thing which took me 3 sleepness nights is that this picture may seem unbalanced, but in fact its fully balanced.
- the proof is of course in the result: the rotor is nicely level as follows from previous published time plots of flapping angle versus time or rotation (I also have a plot of the rotor disk to have a proof of that as part of my reports)
But wat happens, how the understand:
- the total lift diagrams certainly shows a lot of (total) lift on the forward blade
- looking at the distribution one observes that the retreating blade gets all lift from the top while the forward blade gets it from the middle
- why : because of the twist in the blades, when the forward blade flaps such as to reduce lift it gets from the high speeds , the tip gets near zero lift because of twisting. The retreating blade has to coop with a large ineffective area, so it gets all the lift from near the top.
- the middle of the blad has however a far smaller leverage arm than the top, so this is why the rotor, even with those very assymetric pictures is quite in balance.
One thing that triggers my curiousity : the rotor must feel important higher order harmonics:
- tip with large lift alternating with tip with zero or even negative lift
stated otherwise
- center of lift forces shifting all the time from middle to top.
Delta3