Don and Blaine had interesting points in their recent posts. These got me
thinking again.
Don pointed out the increased efficency during circling with higher dihedral
and Blaine pointed out that a gyro can make spiral stability a moot point to
the pilot of any aircraft.
But this question
If one were to adjust the polyhedral in a wing, so that each break angle
was equal (less dihedral than normal for the tip panels), how badly do
you think that would affect the spiral stability of the model? We're
talking about a 2 meter lightweight RE... Outer panels are about 10%
longer than
Ok, I grant you that the Allegro has a good margin,
and that circling CL is, let's say, 0.7 - 0.8.
But I'm still wondering about, let's say, a Bird of
Time, which has a short tail moment and EDA 10, or a
Grand Esprit which has a very low EDA -- and of course
there are others.
For these
A number of people have asked for clarifications or references
on the vertical tail vs spiral stability issue. There aren't
any that I'm aware of. Unfortunately it's a very complex subject.
Here's a writeup I did which expands only on the basic effects.
It's still kinda complicated, but I
Tony Estep writes:
This sez that if your tail moment is 40" and span is
120" and you fly at CL = 1, you need 15 deg of
dihedral to be spirally stable. This is indeed what
Blaine's Crossbow design has, but lots of RES designs
including the Allegro have quite a bit less.
How much spiral stability
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