| 摘要 |
<p>The rudder appendages of ships are vulnerable to damage from external causes particularly when navigating in ice and when in the astern mode. This invention eliminates the traditional pivoted rudder blade which is replaced by a retractile rudder blade or blades capable of being withdrawn into the protection of a ship's hull when not required for steering and of being selectively extended into the propulsion race to the extent necessary to generate a required turning moment.</p> |
