Propellers

Propellers. . For centuries, the only way to move a boat across the water was by oar or by sails, each of which had its drawbacks. Rowing is difficult; sails need wind. Paddlewheels were an improvement in propulsion, but still were inefficient the bigger the boat, the bigger the paddlewheel needed. The introduction of the screw propeller in 1840 revolutionized shipping. A single propeller was smaller than two paddlewheels, it was also cheaper to build and more effective., John Sherwin , The John Sherwin was built in Toledo in 1958 by the American Ship Building Co. for the Interlake Steamship Co. She was named for a senior executive at Pickands Mather and Co., owner of Interlake. Originally 690 feet long, the Sherwin was lengthened by 96 feet in 1973. This straight- deck (not self-unloading) bulk cargo vessel could carry up to 31,500 gross tons of cargo! Moving that much boat and cargo takes a big engine- 8,500 horsepower and a huge propeller. The Sherwin's propeller was cast as a single piece in Toledo, and was at the time the largest single-cast bronze piece in existence. The propeller weighs 21 tons and is 22 feet across.