Rather than using a spring, my turbines use gravity. The tail is weighted to adjust the furling speed, and is mounted on an offset angled hinge pin. The turbine rotor and thrust centerline is also mounted off-center from the yaw so rotor thrust acts in one direction while the tail forces act in the opposite direction. When rotor thrust exceeds tail steering forces the machine turns out of the wind and reduces the amount of swept area exposed to the wind, as well as increasing blade angle of attack, reducing rotor efficiency. These machines furl and limit power to 2,500-3,000 watts in 80 mph winds with no problem. If it exceeds 144V input to the controller, there is also electro-mechanical braking that applies in the form of a three-phase voltage clipper applying additional load to the generator, which in turn more heavily increases load on the rotor, which in turn causes the airfoils to run at higher angle of attack and be less efficient. The voltage clipper will actually fully stall the airfoils if fully applied, stopping the turbine even in very strong thunderstorm winds.
This is a 3.5 meter (11.5 foot) diameter machine:
This is a closer view of the machine with the tower laid down during its annual service:
And a static photo showing how the furling geometry interacts. You can see wind direction from the directional indicator on the anemometer, as compared to the direction the rotor is facing when the machine is furled - the rotor is almost 90 degrees to the true wind direction, which drastically reduces its effective swept area and power output. This photo was taken at a wind speed of about 60 mph
And a photo standing at the base of the tower so you can see the geometry of the tail offset when the machine is in the normal "flying" position