Hi Gents
As a Derjet Cougar owner I'm finding this thread very interesting as I too am having the same dutch roll problem. I have never fitted a gyro to a fixed wing aircraft before but having read Dave and Ali's posts I will be doing now. The question is do I put it in the roll axis or the yaw axis?....On the B757 I fly the dutch roll is damped in the yaw plane exactly as Harry described and yaw damping is how full size swept wing aircraft stop dutch roll. Having said all this I cannot ignore Dave and Ali's advice as they have the time on the swept wing models and regardless of full size aerodynamic principles if the gyro works better in the roll axis you cannot argue as we've all seen Dave and Ali fly. I'm open minded about this and welcome the results of the gyro experiments as Ali hit the nail on the head we want it to look good flying!
Regards
Mark