Question - rudder flutter ?

On Dec 26, 5:31 am, Bertie the Bunyip wrote:

It's done all the time, but it doesn;t have to be at one end and it
doesn't have to be a horn. It also doesn't have to be a 100% balance if
the performance doesn't neccesitate it or if the stab or wing is rigid
enough for flutter not to be an issue within the speed envelope.
But for anythng that goes very fast, you have to have 100% balancing,
which means it's statically balanced at the hinge line.


Even more than 100% is needed in some common planes (e.g. the
Bonanza). In this case a wing roll will be dampened automatically (I
think) -I'd guess it makes the plane feel more docile, but perhaps
you know this plane and can comment. But I disagree with you about one
point, the center of lift of the control surface is still important. I
think this is because the control linkages aren't stiff enough to stop
a control surface flutter. (I am keeping to the question of control
surface flutter and trying to avoid the coupling in of the flying
surface the control is attached to.)
I think you would agree that if the Cl of the surface were ahead of
it's COG control surface flutter would be guaranteed (no linkages
would be stiff enough to control it)? I believe that this mode may be
excited by the disturbed air flowing through the gap between control
surface and wing which slightly reduces the surface lift on one side
which then couples into the potential for the flutter. It would be
felt as a vibration in the stick whereas a wing flutter _might_ not be
felt through the stick at all (esp. if the control surface is 100%
balanced!!)

Nice to have a bit of flying/tech discussion instead of troll lures.

Cheers

leads to . I'll agree that normally the Cl will be behind the COG for
a typical triangular section control surface but if a dynamically
balanced design is sought, the Cl moves much closer to the hinge line
and then the COG may not be far enough forward. I'd suspect this might
have been a big problem with some early WW1 type rudders that looked
to be highly balanced.

Cheers