Nick,. .. .You've brought up some excellent concerns, particularly since they're founded in hands-on experience.. .. .The minimization of the coning angle may be achievable by a combination of blade stiffness, plus blade anhedral (not just tip anhedral) or negative pre-cone. . .. .Your point about high loading and vibration is very much of a concern. As well, I question whether Higher Harmonic Control or Active Blade Control will be able to overcome the blades inertia about the feathering axis, at rates of 1/4 or 1/8th or 1/16th of a rotor's revolution. . .. .The theoretical objective of all this 'stiffness' is to improve the response of the craft to cyclic inputs.. .. ._____________. .`. .`. .`. . <img src="http://www.unicopter.com/super_hug.gif" alt="" /> . .. .Keeping Nick and Lu at arms length
~ or is it ~ Nick and Lu making up?. .`. .`. ._____________. .. .Lu;. .. .Probably very few people have a comprehensive understanding of rotor blade aerodynamics and I certainly don't; but for the heck of it, here goes a little;. . . .Looking at a cross section of a blade (profile), the chord line is a straight line that runs from the leading edge to the trailing edge. On the symmetrical NACA 0012 airfoil the 'Center of Pressure' is located at 25% of chord (25% back from the leading edge). As the blade's angle of attack is varied, the Center of Pressure will not move along the chord line.. .. .On an asymmetrical (cambered) airfoil, the Center of Pressure at zero lift can be ahead or far back from the 25% location (forward or aft camber). As the blade's angle of attack is increased, the Center of Pressure will move, and hence the instability.. .. .A light coverage of this subject is located at; <a href="http://www.cybercom.net/~copters/aero/pressure_patterns.html" target="_blank">http://www.cybercom.net/~copters/aero/pressure_patterns.html</a>. .. .To use the NACA 0012 as an example, the center of mass is in front of the Center of Pressure. If a gust should lift the blade, the inertia of the forward-located mass will want to reduce the blade's pitch angle.. .. .This is starting to move off the topic of fat heavy blades ------ <img border="0" title="" alt="[Smile]" src="smile.gif" />