Bert Willing wrote:

The effect of any control surface is the product of lever x surface.
Longer fuselage (lever) makes up for smaller rudder. Your line of thought
does not work.

Aren't these actually competing effects? Certainly the longer fuse will
have an increased polar moment of inertia about the yaw axis. Also, the
longer fuse *will* present more air-drag resistance to yaw movement, and the
tail will have to be dragged through more air for the same yaw rotation.
Then of course the rudder has more "mechanical advantage" due to the longer
lever arm as you point out.

I think both lines of thought are basically correct. The question is
quantifying one effect vs. the other, I believe. Interesting discussion.

Regards,

-Doug