The predecessor of the stern rudder was the stern oar, which was employed to control the sailing direction of the ship in the Shang Dynasty (16th-11th century BC). The ships excavated in Changsha (Central China's Hunan Province), Guangzhou (South China's Guangdong Province), and Jiangling (Central China's Hubei Province ) all had something in common: At the stern of each ship there was an oar, called the maneuver oar, which was used to control the ship's sailing direction. The handle of the oar, when lengthened, became a rudder. In the application process, the size of the oar was increased, resulting in the real stern rudder.

Though a small device, the stern rudder can make a giant ship move in its own way. Why? For any ship in navigation to turn left, the stern rudder has to be deflexed by an angle in the same direction. In other words, for the ship to turn left, the rudder has to be turned to the left. In this way, the water will press against the surface of the stern rudder - the rudder pressure, which in turn will make the ship turn left.

The stern rudder is of significant importance in the history of shipbuilding, and is seen as one of the three conditions for safe sailing, together with the sail and the compass .

Author: Jessie