Test flight torquen coaxial-system in combination with 18" propellers V-shape design

New 18” propeller with V-shape:
One of the critical problems of a F3P model is the controllability of model at “torque-roll”. We believe that every F3P pilot had already the situation that response characteristic of aileron at torque position was very bad/ no reaction at full aileron deflection. This behavior happens irregular and more or less randomly. This behavior of model is result of flow movements in hall. If the flow movement hit the wing during torque position the model set into rotation. In worst case any counteract with aileron have no influence because total force of flow movement (depends on hit position of wing and flow movement) is too strong. In this case model could stand still at full aileron deflection.
Furthermore the F3P model has a limited functioning of ailerons at torque position because only the part of aileron is working which is in airflow of propellers. The larger working area of aileron (distance from middle of fuselage to aileron) is the better is controllability of model at torque position. A larger working area of aileron needs less deflection of aileron during torque position and less aileron deflection has the effect of less adjustment of engine power. Also a positive effect of less aileron deflection is the less impact at rudder and elevator (less turbulence).
The new coaxial-system configurations with 18” V-shape propellers are taken in to account to improve several critical conditions.

Improved controllability at torque position:
The airflow from 18” propellers is bigger in comparison to 16” propellers and improve the controllability of model at torque position.

Improved brake performance downstairs:
Furthermore 18” propellers provide a better braking downstairs performance because of size (diameter/ width of propeller).

Similar/ improved behavior in figure “turn”:
One critical aspect of bigger propellers is rotation energy (depends on angular velocity and moment of inertia Erot = ½ x J x ω²) which express for example at figure “turn”.
The 18” propellers are heavier which results in higher moment of inertia (weight difference 16” vs. 18” propeller is 0,5g).
The coaxial-system configurations with 18” propellers are running with significant lower speed (rpm) which results in lower angular velocity.
The angular velocity has square influence at rotation energy. Due to significant speed reduction the rotation energy of 18” propellers is lower which result in similar or even better behavior of model at figure “turn”.

Improved stability of model in torque/ up- and downstairs condition:
The new 18” propellers has a slightly V-shape forwards. During several flight tests we recognize that stability of model has been improved in several conditions (like a toy top).
At the video you can see the model behavior in torque position is very neutral.
Furthermore you see can see that model behave also neutral even if you go upstairs/ downstairs in torque position (no correction via rudder and elevator).