Theory of Operation
The Autostream feathering yacht propeller is designed especially for sailing yachts.
It may be fitted in the normal manner to conventional propeller shafts with ahead and astern gearboxes. The hub blank may be machined in the normal way with taper and key to suit the particular shaft.
The blades turn in the hub on their own axis some half a turn from the ahead position through ‘feather’ to the astern position. This movement is imparted to the blades by the shaft turning through a limited angle within the hub, and no control is required apart from the gear lever. When the shaft is put ahead, the blades are turned to a positive pitch position and drive the yacht ahead.
With the yacht under way, and the shaft stopped, the propeller overruns the shaft a little until the blades assume the feathered position. In this situation the blades give no turning motion to the propeller and will not move from ‘feather’ unless the shaft is rotated by the engine.
When the shaft is put astern the shaft turns further in the hub and the blades complete their half turn from ahead position to the astern position. It will be seen now that the propeller is similarly ‘handed’ (right or left) in the ahead and astern positions, and as the shaft is turning in reverse, astern position is achieved.
The stops that limit the shaft rotation in the hub are controlled with two set screws and lock nuts. By altering the setting of these screws, the pitch of the blades are readily and simply adjusted to best suit the engine and hull characteristics.