Mtnman... for the moment consider an aircraft in a slip. I know you had to have slipped an airplane or two. In a right hand slip (right wing low) the nose is left of the velocity vector and you are holding left rudder. What happens in this case is lift is generated by the vertical stabilizer and it has a corrective measure upon the yaw. So if you dont hold the left rudder then the plane will yaw to the right and restore the moment (so to speak) which will cause the airplane nose to point into the relative wind and return the sideslip angle to zero. Notice the plane does not roll to the right except the roll you add with aileron in order to hold the slip.
Im not sure but I dont think the rudder on the F-14 is very effective either (at yawing with coupled roll).
Anyway take the example of the slip I used and apply it to an aircraft with one stabilizer missing and you will see there is a pretty big difference.
EDIT: The F-14 actually has a counterpart in WWII that you can consider to be very similar in trait. The P-38 has the vertical stabilizers placed directly behind the propellers for increased stability. In a similar manner the F-14 has the twin stabilizers mounted where they can make use of wingtip vortices and flow entrainment caused by the exhaust of the two engines. Both of these airplanes are making use of the sidewash gradient that should become obvious in the slipping example I gave.
Sorry about the long time between replies, I'm working this weekend, and with the drive it's a 15hr day... Yes, I've flown slips. RC as well as "full-size" planes, and of course in the game.
The slip argument is a great example, but actually illustrates
my point better than yours....
Again, you're not going to see the left rudder/right roll effect with a "normal" plane, because it has wings, and those are overcoming that effect. get rid of the wings (back to the plastic straw, where it's really pretty obvious), and you would. Just because the effect is canceled by the wings though, doesn't mean it isn't there. It's the same rolling effect seen with one elevator without a countering surface (opposite elevator) to overcome it...
The slip proves the point actually. In a right-wing low slip, with the nose pointed to the left, the very reason the nose
is left is due to the
right-push of the
left rudder. While the nose is to the left, it's only because the left rudder forces the tail
right, out into the slipstream, and with the plane pivoting around it's yaw axis, the nose goes left...
"Lift" isn't generated by the vertical stab/rudder. That's not what forces it out into the slipstream, and that's not what brings it back in line. "Lift" would "draw" it left or right, which doesn't happen. It's "pushed" out there by the deflected rudder, and "pushed" back in line when the rudder is released. A much better analogy is a weather-vane. Lift is also the force that pulls opposite of gravity, but what matters here is that the tail isn't "drawn" anywhere, it's pushed/forced.
That very "push" is what leads to a left-rudder/right roll force. In order for there to be no roll force, the rudder would need to exert equal force above and below the aerodynamic center-line. If it exerts more force either above or below that center-line, a roll force will be present. It's exactly the same argument as the one this thread began with... The reason you don't see the roll effect from the elevators is because they "normally" overcome each other. The reason you don't see it from the rudder is because the wings overcome it...
Back to the straw again (you really should try it, it illustrates the point quite nicely). If you only put one "stabilizer" on it, bent to simulate control surface deflection, and give it a toss, you'll see two things (and it doesn't matter if you toss it with the stabilizer horizontal and call it an elevator, or toss it with the stabilizer vertical and call it a rudder, the effect is the same). For one, the deflected surface will push the "tail"
away from the deflected surface. Always. Second, it will exert a roll force, and it will also be away from the deflected surface. Always.
The final result is a spinning straw that rolls away from the deflected surface (exactly like the opening post argues) as well as "rotates" (for lack of a better word, I'm tired). Imagine the tip of the straw as the tip of a funnel, with the "tail" of the straw following a path around the top of the funnel. The speed of the roll, and the relation it has with the "rotation" is variable, and depends on the size of the surface, it's height/distance that it protrudes from "center", the speed of the "toss", the balance point/CoG of the straw, and the time "in flight". I imagine if it had a long enough "flight", it'd try to rotate around the CoG, almost like two funnels taped together, large open ends away from each other. With the smaller funner being the front of the "plane" and the larger being the rear.
That rotation around the CoG is exactly what's happening in a slip, where the nose is force left with left rudder, all because the tail is being forced right (with left rudder).
