How does controllable pitch propellers work in a ship.?

Question

How does controllable pitch propellers work in a ship.?

Answer 1

How it works Rpm is set for torque and the prop pitch is increased for Speed>& decreased for power.

Answer 2

Exactly the same as they do on a helicopter. Low pitch means higher revs for same distance, but more strength. High pitch means lower revs for same distance, but low strength. The High pitch would be used once required speed is achieved and you wish to lower engine RPM and still maintain speed.

Answer 3

Controllable pitch propellers always spin at the same RPM barring the short time they take to come up to speed when started up, then stop after being shut down.  The blades are swiveled at the hub of the propeller to provide ahead or astern thrust.  The axis around which the blades pivot is drawn from the center of the hub through the tip of the blade.   0 pitch = no propulsion forward or aft, max positive pitch is full ahead, and max negative pitch is full astern.  They are often used when the power plant the ship has employed is not designed to be reversed.  They are also used in tunnel bow thrusters.  Controllable pitch propellers have very quick response to engine commands.  In addition, you don’t have to worry about stopping and reversing your diesel when you want to go from ahead to astern or vice versa.  Changing direction like I just described on a fixed pitch prop ship does more then take up time when maneuvering it takes up start air of which you the engine room has a limited quantity in there start air tanks.  All this being said they are not as efficient as a normal prop, but for maneuvering there handy. All of the mechanics in the hub that allow the blades to tilt can fail though and then you’re out of luck.  For the best in maneuvering look into fully azmuthing thrusters or Azipods.