Have a couple of questions for all you aerodynamical rotorheads out there that I've always wondered about, but haven't been able to find answers to.
1. One of the reasons heli's can't go very fast is because the retreating blade will have an unnaturally high angle of attack as to push air through the disc, causing it to stall. To increase stall resistance in FW, slats are often mounted to wings. Why couldn't you mount slats to the blade that pop out when the blade retreats?
2. Most modern rotors in helicopters seem to have constant chord blades where the tip has been twisted donwards towards the tip so as to produce less lift the further away from the hub you get. But the same thing could be achieved by having the chord change (and the twist remain unchanged) - by narrowing the blade the further you go out from the hub, the less lift it would produce (this was common in earlier helicopters). A twisted blade must be so much more expensive and complicated to make, so why was the changing chord design abandoned?
3. Also, older helicopters often had wooden blade rotors, and I think a few helicopters might still do (Brantly?). But I can't recall reading or hearing anywhere that wooden blades were more susceptible to failures than metal ones. What was the main reason wooden rotor blades were abandoned?
4. Rigid rotor question. As I understand it, in a rigid rotor system, lag and hinging is 'absorbed' by the blade itself, eliminating the need for dampers and such. Now, if I just took a normal, fully articulated rotor and removed the dampers for something solid and beefed up the blades, wouldn't this become a rigid rotor? If so, why aren't all manufacturers making rigid rotor systems, since they seem to have less moving parts that can start to misbehave?
Thank you.
