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Why not an upside down rudder?

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HumanPoweredDesigner

Well-Known Member
Joined
Sep 6, 2009
Messages
1,030
Location
Arizona
When you turn the rudder to yaw left, the rudder torques the plane to bank right, since the rudder is on top. That means more work for the ailerons. If the rudder were below the fuselage, it would torque the plane to bank left, which is the intended direction. So why is it not used more?

Also, unlike the tail wings, the rudder does not need leverage. I'm pretty sure it will yaw the plane just as fast if it is in close the fuselage, or far back. So, since the fuselage needs streamlining anyway, why not make the back of it the rudder? Less pressure drag and less skin drag that way.

My airplane will be a high wing with a canard, and the rudder will be the back bottom of the fuselage. The main airfoil will be high lift (max Cl = 2.3), and I'll point the nose up for landings. The front will be transparent, and there will be a pusher prop right above and behind the rudder. I will have ailerons inboard on the canard, but none on the wings. I think with the upside down rudder and high wing and properly designed canard the plane will be very well behaved and not need ailerons. Another reason I don't like ailerons is they have adverse yaw during banking. With all the control surfaces in close to the cockpit, it will be a very simple, strong design.

I just don't know exacly how manuverable it will be, even with a small span. What do you guys think? I don't think the canard ailerons are necessary for turns, but they do improve turns if they don't stall. My goal is a span of 30 feet, wing loading of 4 pounds, and 20 hp. I want to use something like the S1223 airfoil and control lift and drag by using the canard to bring the nose up or down.
 
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