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FLUTTER

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stuart fields

Well-Known Member
Joined
May 30, 2008
Messages
295
Location
Inyokern California
Here is a NASA video on flutter that is very interesting. Poorly designed rotor blades with the c.g being too far aft are potential flutterers. Look also at the propeller-shaft flutter demonstrations. There are critical speeds for all rotating shafts that need to be avoided by a safe margin. The Safari has a critical speed in the tail rotor shaft that created problems in balancing the tail rotor. The protocol of "Add Opposite" when applying corrective wt that worked so well on the main rotor got reversed on the tail rotor to "Add Same". The Safari has a horizontal stab that has the spar mounted too far forward in the airfoil. Over time the mounting rivets would loosen caused, I believe, by the unit trying to flutter under certain flight regimes. When I built mine, I moved the spar to a more balanced position and never had the rivets loosen up. Also the Rotorway that I presently own has a similar issue with its horizontal stab. Fixes have used a bracket to attach the trailing edge of the horizontal stab to the tail boom. This whole area of aerodynamics gets ignored by a majority of amateur builders as well as more than one kit manufacturer. Be very leery of a kit mfr. who uses the phrase: "None have broke yet" as his justification for his design.

https://youtu.be/jW8I2hX4GSs
 
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