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Old 02-26-2002, 09:53 PM
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Join Date: Dec 2001
Location: Punta Gorda, FL
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Default Flutter

Every control surface and its associated linkages has a natural frequency of vibration. The stiffer and lighter the system, the higher the frequency. When aerodynamic forces produce deflection that also is periodic, the stage is set for flutter. Blunt trailing edges and rounded trailing edges can produce vortex shedding. The frequency of vortex shedding is a function of airspeed. When the natural frequency of vibration of the mechanical system matches the natural frequency of vortex shedding, flutter results. There are other, more common aeroelastic, causes of flutter too.

Use sharp, gradually tapered trailing edges to minimize vortex shedding and reduce weight. Make the mechanical system as light and stiff as you can. This will generally raise the natural frequency of the mechanical system well above the vortex shedding frequency in models. Mass balancing around the hinge line makes the mechanical system aperiodic. Aerodynamic balance (hinging through the aerodynamic center) minimizes the aerodynamic forces.
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