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Re: feather asymmetry

On Jul 7, 2014, at 2:52 AM, Tim Williams <tijawi@gmail.com> wrote:

> If I'm understanding this correctly... if the lift is incapable of
> counteracting weight, then flight cannot be sustained.

Absolutely. My point was just that lift can also be oriented to do other 
things, such as produce pitch, roll, and yaw. This is not mutually exclusive 
with supporting weight with lift (i.e. sustained flight, be it powered or 
unpowered). Control functions can also be engaged in a context that does not 
include sustained flight, however, which I think was your original point.

>> What might make controlled descents and other transient behaviors less 
>> sensitive to low levels of
>> feather asymmetry is simply the timing - delaying stall is less important if 
>> the maneuver is very brief.
> If this low feather asymmetry had a selective advantage for transient
> "pre-flight" behaviors, then it offers a transition to the highly
> asymmetrical vane that's important in powered flight.

Indeed. So far, there is little evidence that low feather asymmetry has a 
measurable advantage. However, as Tom Holtz noted, if limited asymmetry and 
symmetry are functionally the same, there isn’t selection promoting symmetry,