wrote:
On Jan 3, 12:39 pm, Eric Greenwell wrote:
wrote:

Here is the sailplane wing flutter video I was referring to:
http://www.youtube.com/watch?v=kQI3AWpTWhM
You can see the flutter is symmetric with several waves from tip to
tip.
When I pause the video, I can see one tip is up while the other tip is
down. Isn't that asymmetric flutter?

Your definition is, of course, correct Eric. I looked to me like once
the flutter was established it was symmetric. I'll take another look.
I think the symmetry or assymmetry may be aside to the main points of
the discussion as it isn't clear to me that it would necessarily
indicate anything one way or the other on the issue Andy raised about
control surface interaction and certainly not on the ballast question.

Looking at it again, I can see the ailerons going to full deflection
(one up, one down, of course). That might be what is driving the wing
oscillations asymmetrically. If the oscillation was symmetric, I suspect
the ailerons would not be deflecting, since they can't both go down at once.

I am curious about ballast. My first guess is it lowers the oscillation
frequency because that's what mass usually does to a resonant mechanical
system, but frankly, I haven't a clue, and don't find any mention of
it's effect in FOSD, either. Either way, it's kind of scary to see how
fast it flutters.

--
Eric Greenwell - Washington State, USA
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