The oar is a propulsion tool for ships. It is developed and evolved based on the rudder oar. After the rudder oar was lengthened, the operation method evolved from "rowing" to fish-tail "rocking", resulting in the unique Chinese "oar". The invention of the oar is one of China's major contributions to world shipbuilding technology.
The specific time when the oar originated in China is still difficult to determine, and the age of its earliest appearance is still unknown. Legend has it that Lu Ban saw the fish waving their tails in the water and cut wood into a oar.
According to records in ancient Chinese books, the earliest appearance of oars was in the Han Dynasty. According to Liu Xi's "Shi Ming" of the Eastern Han Dynasty, the word "湩" has been explained, and it is believed that the force it generates is along the direction of the ship's spine.
The shape of the oar is a bit like an oar, but it is larger. It is usually supported on the eaves of the stern or side of the ship. The cross section of one end entering the water is bow-shaped, and the other end is tied to the ship. Shake the oar eaves rope by hand to make the oar board extending into the water swing left and right. When the oar swings, a pressure difference occurs between the front and rear parts of the boat that are in contact with the water, forming thrust to push the boat forward, just like a fish swinging its tail forward. The ancients had a saying of "one oar and three oars", believing that the efficiency of an oar can be three times that of an oar, because the change from oar to oar is actually from intermittent paddling to continuous paddling, which improves efficiency.
The oar is a propulsion tool that is superior to the oar. It is a continuous propulsion tool and has the function of steering the ship. Some British experts believe that the invention of the propeller was inspired by the oar. Europeans were inspired to invent the propeller after seeing the Chinese using oars. The British expert's statement is reasonable. The blades of a propeller that rotate intermittently are very similar to a paddle sliding in the water.