Propeller

A propeller is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a boat through water or an aircraft through air.
The blades are shaped so that their rotational motion through the fluid causes a pressure difference between the two surfaces of the blade by Bernoulli's principle which exerts force on the fluid. Most marine propellers are screw propellers with helical blades rotating on a propeller shaft with an approximately horizontal axis.

History

Early developments

The principle employed in using a screw propeller is derived from stern sculling. In sculling, a single blade is moved through an arc, from side to side taking care to keep presenting the blade to the water at the effective angle. The innovation introduced with the screw propeller was the extension of that arc through more than 360° by attaching the blade to a rotating shaft. Propellers can have a single blade, but in practice there is nearly always more than one so as to balance the forces involved.
The origin of the screw propeller starts with the first records of a water screw, or screw pump, dates back to Ancient Mesopotamia, a cuneiform inscription of Assyrian King Sennacherib describes casting water screws in bronze. This is consistent with classical author Strabo, who describes the Hanging Gardens as watered by screws. Later, Archimedes used a screw to lift water for irrigation and bailing boats, so famously that it became known as Archimedes' screw. It was probably an application of spiral movement in space to a hollow segmented water-wheel used for irrigation by Egyptians for centuries. Later, modern propeller designs usually began with truncating a long screw at the tip.
Additionally, a flying toy, the bamboo-copter, was enjoyed in China beginning around 320 AD.
In 1661, Toogood and Hays proposed using screws for waterjet propulsion, though not as a propeller. Robert Hooke in 1681 designed a horizontal watermill which was remarkably similar to the Kirsten-Boeing vertical axis propeller designed almost two and a half centuries later in 1928; two years later Hooke modified the design to provide motive power for ships through water. In 1693 a Frenchman by the name of Du Quet invented a screw propeller which was tried in 1693 but later abandoned. In 1752, the Academie des Sciences in Paris granted Burnelli a prize for a design of a propeller-wheel. At about the same time, the French mathematician Alexis-Jean-Pierre Paucton suggested a water propulsion system based on the Archimedean screw. In 1771, the steam-engine inventor James Watt in a private letter suggested using "spiral oars" to propel boats, although he did not use them with his steam engines or ever implement the idea.
One of the first practical and applied uses of a propeller was on a submarine dubbed which was designed in New Haven, Connecticut, in 1775 by David Bushnell, a Yale student and inventor, with the help of Isaac Doolittle, a clock maker, engraver, and brass foundryman of New Haven. Bushnell's brother Ezra Bushnell and Phineas Pratt, a ship's carpenter and clock maker, constructed the hull in Saybrook, Connecticut. On the night of September 6, 1776, Sergeant Ezra Lee piloted Turtle in an attack on in New York Harbor. Turtle also has the distinction of being the first submarine used in battle. Bushnell later described the propeller in an October 1787 letter to Thomas Jefferson: "An oar formed upon the principle of the screw was fixed in the forepart of the vessel its axis entered the vessel and being turned one way rowed the vessel forward but being turned the other way rowed it backward. It was made to be turned by the hand or foot." The brass propeller, like all the brass and moving parts on Turtle, was crafted by Doolittle.
In 1785, Joseph Bramah of England proposed a propeller solution of a rod going through the underwater aft of a boat attached to a bladed propeller, though he never built it.
In February 1800, Edward Shorter of London proposed using a similar propeller attached to a rod angled down temporarily deployed from the deck above the waterline and thus requiring no water seal, and intended only to assist becalmed sailing vessels. He tested it on the transport ship at Gibraltar and Malta, achieving a speed of.
In 1802, the American lawyer and inventor John Stevens built a boat with a rotary steam engine coupled to a four-bladed propeller. The craft achieved a speed of, but Stevens abandoned propellers because of the inherent danger in using the high-pressure steam engines. His subsequent vessels were paddle-wheeled boats.
By 1827, the Czech inventor Josef Ressel had invented a screw propeller with multiple blades on a conical base. He tested it in February 1826 on a manually-driven ship and successfully used it on a steamboat in 1829. His 48-ton ship Civetta reached 6 knots. This was the first successful Archimedes screw-propelled ship. His experiments were banned by police after a steam engine accident. Ressel, a forestry inspector, held an Austro-Hungarian patent for his propeller. The screw propeller was an improvement over paddlewheels as it wasn't affected by ship motions or draft changes.
John Patch, a mariner in Yarmouth, Nova Scotia, developed a two-bladed, fan-shaped propeller in 1832 and publicly demonstrated it in 1833, propelling a row boat across Yarmouth Harbour and a small coastal schooner at Saint John, New Brunswick, but his patent application in the United States was rejected until 1849 because he was not an American citizen. His efficient design drew praise in American scientific circles but by then he faced multiple competitors.

Screw propellers

Despite experimentation with screw propulsion before the 1830s, few of these inventions were pursued to the testing stage, and those that were proved unsatisfactory for one reason or another.
In 1835, two inventors in Britain, John Ericsson and Francis Pettit Smith, began working separately on the problem. Smith was first to take out a screw propeller patent on 31 May, while Ericsson, a gifted Swedish engineer then working in Britain, filed his patent six weeks later. Smith quickly built a small model boat to test his invention, which was demonstrated first on a pond at his Hendon farm, and later at the Royal Adelaide Gallery of Practical Science in London, where it was seen by the Secretary of the Navy, Sir William Barrow. Having secured the patronage of a London banker named Wright, Smith then built a, canal boat of six tons burthen called Francis Smith, which was fitted with his wooden propeller and demonstrated on the Paddington Canal from November 1836 to September 1837. By a fortuitous accident, the wooden propeller of two turns was damaged during a voyage in February 1837, and to Smith's surprise the broken propeller, which now consisted of only a single turn, doubled the boat's previous speed, from about four miles an hour to eight. Smith would subsequently file a revised patent in keeping with this accidental discovery.
In the meantime, Ericsson built a screw-propelled steamboat, Francis B. Ogden in 1837, and demonstrated his boat on the River Thames to senior members of the British Admiralty, including Surveyor of the Navy Sir William Symonds. In spite of the boat's achieving a speed of 10 miles an hour, comparable with that of existing paddle steamers, Symonds and his entourage were unimpressed. The Admiralty maintained that screw propulsion would be ineffective in ocean-going service, while Symonds himself believed that screw propelled ships could not be steered efficiently. Following this rejection, Ericsson built a second, larger screw-propelled boat, Robert F. Stockton, and had her sailed in 1839 to the United States, where he was soon to gain fame as the designer of the U.S. Navy's first screw-propelled warship,.
Apparently aware of the Royal Navy's view that screw propellers would prove unsuitable for seagoing service, Smith determined to prove this assumption wrong. In September 1837, he took his small vessel to sea, steaming from Blackwall, London to Hythe, Kent, with stops at Ramsgate, Dover and Folkestone. On the way back to London on the 25th, Smith's craft was observed making headway in stormy seas by officers of the Royal Navy. This revived Admiralty's interest, and Smith was encouraged to build a full-size ship to more conclusively demonstrate the technology.
was built in 1838 by Henry Wimshurst of London, as the world's first steamship to be driven by a screw propeller.
The Archimedes had considerable influence on ship development, encouraging the adoption of screw propulsion by the Royal Navy, in addition to her influence on commercial vessels. Trials with Smith's Archimedes led to a tug-of-war competition in 1845 between and with the screw-driven Rattler pulling the paddle steamer Alecto backward at.
The Archimedes also influenced the design of Isambard Kingdom Brunel's in 1843, then the world's largest ship and the first screw-propelled steamship to cross the Atlantic Ocean in August 1845.
and were both heavily modified to become the first Royal Navy ships to have steam-powered engines and screw propellers. Both participated in Franklin's lost expedition, last seen in July 1845 near Baffin Bay.
Screw propeller design stabilized in the 1880s.

Aircraft

The Wright brothers pioneered the twisted aerofoil shape of modern aircraft propellers. They realized an air propeller was similar to a wing. They verified this using wind tunnel experiments. They introduced a twist in their blades to keep the angle of attack constant. Their blades were only 5% less efficient than those used 100 years later. Understanding of low-speed propeller aerodynamics was complete by the 1920s, although increased power and smaller diameters added design constraints.
Alberto Santos Dumont, another early pioneer, applied the knowledge he gained from experiences with airships to make a propeller with a steel shaft and aluminium blades for his 14 bis biplane. Some of his designs used a bent aluminium sheet for blades, thus creating an airfoil shape. They were heavily undercambered, and this plus the absence of lengthwise twist made them less efficient than the Wright propellers. Even so, this may have been the first use of aluminium in the construction of an airscrew.