Furling geometry

[Walter]

I think I've got a handle on the back angle; the tilt of the tail bearing away from the rotor plane. This determines the balance between the rotor offset torque and the weight of the tail and therfore the wind speed at which furling begins.

But sometimes (not always) a side angle is mentioned, that is a sideways shift of the tail bearing away from the yaw axis, opposite the rotor offset and back from the rotor plane.

Is this an essential part of the furling process or is it just to balance off the standing torque due to the rotor offset?

[RP]

With the back angle only, the offset of the turbine would tend to put the unit unit in partial furl all the time,  The offset force on the turbine would make the unit yaw until the tail climbed up high enough from the back angle to balance it.

The side tilt provides a preload to keep the tail pointed straight (against the stop) until the turbine offset generates enough force to begin the furling process.  Generally the idea is to keep the tail straight until you hit 20 or 30 mph wind speed for example.

Hope this helps