Sysser 62 hull geometry ?

yes, maybe I didn't explain that correctly. The initial angle of attack coincides with the yaw angle, another thing is how the flow develops along its surface which can generate an apparent angle of attack. There is obviously a lateral force even with zero yaw angle when heeled due to the asymmetry of the hull wetted surface, which effectively modifies the flow field along the hull and appendages. In my case I didn't tested the heeled geometry for zero yaw angle so I didn't get a negative side force in the rudder, in all yaw angles that I tested the rudder generated windward side force. By "optimizing" the methodology I didn't introduce several errors because the obtained side force matched the towing tank lateral forces within a 1%.