Igor,
regarding data: The incidences of Motor, Wing, Flaps, Stabilizer, Elevator, Fin and Rudder all are 0°.
Power to the motor 431 W. At 9234 rev/min the theoretical torque to the shaft would be 0,446 Nm. Plettenberg eta at this operating point 87 %, so the torque should be 0,388 Nm or 39,55 g.m.
The distance between the suspension points was 65 cm, the reading at the scale was 63 grams. Torque on the model: 41 g.m.
I admit that it would be more accurate to have torque sensor between fuselage and motor, but I do not have access to such equipment… But if there were any spiral flow effect, I would have expected a lower reading.
If we define hinging as a sudden simultaneous rotation about all three axes, then it would be nice if we could sort out the cause regarding each of the three axes. Well, with my measurement I tried to find out if there is any unexplainable torque about the longitudinal axis.
Maybe somebody should start to make a mathematical model of F2B flight??