Calling All Aerodynamicists

[salem]

Here is the problem: When flying at full throttle, I am unable to apply left rudder . This is due to the prop-wash hitting the left-hand side of the rudder. Rudder control is OK when I decrease the throttle.

My solution is to increase the area of the aerodynamic balance of the rudder. On my a/c this is a horn-balance (an extension of the rudder ahead of the hinges).

Is there a downside in increasing the area of the horn-balance? Currently the horn-balance area is 18.75% of the rudder area. I would like to increase it to 25%. The textbooks recommend that the horn-balance area is kept at under 20% of the rudder area.

The a/c is a 3-axis pusher with a Rotax 503 with a B-type gearbox, and a prop with a clockwise rotation (looking from the rudder).

[Abe]

Hi Salem!
My Beaver has the same configuration, but even without aerodymic balance on its huge rudder I effortlessly get full deflection either way at full throttle.
Maybe you have too little leverage in the rudder linkage?
Increasing aerodamic balance might induce rudder flutter, as the air is very turbulent behind the pusher prop. (The Beaver's tail shakes visibly under power, and the vertical fin front mounting bracket support (aluminium) showed metal fatique cracks at 500hrs, replaced with 304 stainless steel.)
FlySafe!
Abe.