We noticed a knocking sound from our wind turbine and thought it might be a disk rubbing on the stator but the problem turned out to be the nuts that were holding on the blade assembly. Two had disappeared and of the two that were left only one was tight. There is no chance to see if the missing nuts fell anywhere near the mast as the ground is well covered with snow at the moment.
The tail is a bit of an experiment and the turbine has been flying with it since November. It’s heavy gauge plastic coated corrugated sheeting, dimensions are 98x72cm and it is around the same weight as the recommended plywood tail. It seems to be furling on time but could be a bit bigger for holding the turbine better into the wind.
We use both the spring rings washers type and locktight. you have to make sure the surface is completely clean of oil etc before applying it. I also think that one reason for loosing the nuts, may be extra vibrations in the blades and may be some wobble of the blades due to imperfect magnet disk parallelism. sometimes disk are not perfectly flat. we test the parallelism of the outer magnet disk and correct with shim on the air gap spacer. Hope it is helpful.
Noam