Why the humble screw propeller, not the paddlewheel, made ocean steamers work
Early steamships churned the sea with paddlewheels, which lost much of their power whenever cargo made the hull sit deeper. Swapping them for a fully submerged screw propeller, whose efficiency barely changes with depth, was the key step that let steam conquer the oceans and helped drive a surge in global trade.
A steamship, or steamer, is an ocean-going vessel driven by steam engines turning propellers or paddlewheels. The prefix PS marks a paddle steamer and SS a screw steamer, though many people wrongly read SS as steamship; motor vessels use MV. Freed from dependence on the wind, steamers opened new routes and have been called a major force behind the first wave of trade globalisation, from 1870 to 1913.
Smaller steamboats came first. Denis Papin conceived them in the early 18th century, and the Pyroscaphe of 1783 was the first working paddle steamer. Richard Wright's Experiment, a converted French lugger, made the first sea voyage by steamboat in July 1813, from Leeds to Yarmouth. The 116-ton Aaron Manby, built in 1821, became the first iron vessel to go to sea, crossing the Channel and reaching Paris on 22 June 1822 at about 8 knots.
Crossing the Atlantic took several attempts. The American SS Savannah reached Liverpool on June 20, 1819, but sailed most of the way. The Dutch-owned Curaçao, a wooden ship of 438 tons with two 50-horsepower engines, may have been first to make the trip substantially under steam, spending 11 days under power between Hellevoetsluis and Paramaribo in 1827; the Canadian Royal William of 1833 is another contender. Isambard Kingdom Brunel's paddle steamer Great Western of 1838 was the first built for scheduled transatlantic service, opening the ocean liner era.
Francis Pettit Smith's SS Archimedes of 1839 was the first screw-driven steamship for open sea and persuaded the Royal Navy to adopt propellers; Thomas Clyde introduced one to America in 1844. Making the switch required engines delivering power low down to a propeller shaft, which Brunel's Great Britain managed with a chain drive after a late design change. Shafts also needed a sound stern tube where they pass through the hull. When the Great Eastern's bearing wore badly on her first crossing, a water-lubricated bearing of lignum vitae wood, patented in 1858, solved it and remains standard.
Source: Steamship
