What seems ordinary today was quite revolutionary 200 years ago. Thanks to the dedication and ingenuity of great thinkers on water propulsion, we have ships that run at around 45-60% efficiency. That can be a lot higher is we continue to develop the concept - and we need to in order to avert a climate meltdown, aiming for 70-80%.



Paddle steamers are much like rotary oars, being drag devices. They are good for shallow river boats even today, where they are less likely to snag on weeds than unguarded propellers. The development of paddle wheels got engineers thinking about machinery as propulsion over sails - as being normal - so a great leap forward, in relieving able bodied seamen from going aloft to furl sails and the like.


The development of the propeller overtook the efficiency of paddles due to the efforts of a number of inventors. This is typical of the development of most technology, where it is the collective human brain that moves us along on the shoulders of intellectual giants.


A ship’s screw acts on water that is moving around the hull. As a ship moves forward she disturbs the laminar flow of the water with turbulence at the aft of the hull, that materially affects the screw’s performance because of the way the water approaches the screw. This was not appreciated with paddle wheels set on either side of a hull.


In addition, where early propellers were partly drag devices, the science of airfoils, or hydrofoils was not appreciated until wing experiments on aircraft, by (for example) the Wright Brothers in the late 1800s. Before that propeller blades included foil properties by accident.



  Tug of War as conclusive proof of performance


JOHN ERICSSON improved ship design with screw-propellers. However, the Admiralty disapproved of the invention as being disruptive. As a result, in 1839, Ericsson took his talent to New York where Captain Robert Stockton obtained funding for a 700-ton sloop called the USS Princeton. Approaching completion of this ship Stockton began working to force Ericsson from the project having avoided letting outsiders know that Ericsson was the inventor. Such struggles are commonplace for innovators whose work and reputation suffers, but is nevertheless noteworthy and Stockton then did all he could to prevent Ericsson from being paid for his work because he knew that well funded Ericsson would triumph and that that success would then expose his misdirection.


Despite giving Ericsson a cold shoulder, the British Admiralty knew that screw propulsion had obvious advantages for warships. Paddle wheels were exposed to enemy fire in combat, whereas a propeller and its machinery were tucked away below deck. The space taken up by paddlewheels restricted the number of guns a warship could carry, thus reducing its broadside. Stubbornly the Admiralty refused to budge until Ericsson was otherwise engaged. Then in 1840 the world's first propeller-driven steamship, SS Archimedes, successfully completed a series of trials against fast paddle-wheelers. That demonstration got the Navy's attention and they wanted more data. Finally, in 1845 the British Navy decided to compare the two systems conclusively. For the comparison, two near equal ships were selected. In the paddlewheel corner was the champion, HMS Alecto, weighing in at 880 tons, with a 200 hp steam engine. The challenger was the propeller driven HMS Rattler, also weighing in 880 tons and also with a 200 hp steam engine.

The most famous trials took place in March 1845. Over an 80 mile course, the Rattler easily won a one-on-one race with Alecto, by 23.5 minutes. In a 60 miles race, using a different propeller design and against strong winds and seas, Rattler won by 40 minutes. The final and most exciting round, more a publicity stunt, had the two ships cabled together stern to stern, for a tug-of-war. The Alecto reached full power quicker, and pulled the Rattler backwards for 5 minutes until the Rattler reached full steam, and brought the Alecto to a stop. With the Alecto's paddlewheels turning furiously, the Rattler then towed the Alecto backwards at a speed of more than 2 knots (3.7 km/h). Six years after the British Navy scoffed at Ericsson's propeller, all future RN ships were so equipped. Fast forward to 2014 and autonomy, and a more enlightened mood.



The screw propeller was introduced in the latter half of the 18th century. David Bushnell's invention of the submarine (Turtle) in 1775 used hand-powered screws for vertical and horizontal propulsion. Josef Ressel designed and patented a screw propeller in 1827. Francis Pettit Smith tested a similar one in 1836. In 1839, John Ericsson introduced the screw propeller design onto a ship which then sailed over the Atlantic Ocean in 40 days. Mixed paddle and propeller designs were still being used at this time (vide the 1858 SS Great Eastern).


In 1848 the British Admiralty held a tug of war contest between a propeller driven ship, Rattler, and a paddle wheel ship, Alecto. Rattler won, towing Alecto astern at 2.8 knots (5 km/h), but it was not until the early 20th century paddle propelled vessels were entirely superseded. The screw propeller replaced the paddles owing to its greater efficiency, compactness, less complex power transmission system, and reduced susceptibility to damage (especially in battle).



Tug Of War British Admiralty


TUG OF WAR - The Rattler and Alecto performance experiment of 1848, where the propeller ship pulled the paddle steamer backwards at 2.8 knots. Still the British stick in the muds turned a blind eye, most likely so as not to upset existing contracts and special arrangements pertaining thereto.





1794 - A triple-threaded screw was patented by William Lyttleton. This propeller was designed for mounting in a frame attached to the ship’s hull. It was to have been driven by manually-operated winches through a system of ropes and pulleys. A boat fitted with this device was tried in Greenland Dock, London, but a speed of only two miles an hour was attained.





A triple threaded screw was patented by William Lyttleton in 1794. It was mounted in a frame that could be attached to the bow, stern or sides of a ship a bit like an outboard engine. The screw was designed to be operated manually by ropes from winches on the vessel’s deck.



1800 - A similar device was invented by Edward Shorter. His design consisted of a two-bladed propeller on an inclined shaft supported by a buoy at the stern of the vessel. The inclined shaft carrying the propeller was driven through a universal joint by a second shaft on the ship above the water-line. The transport Doncaster was fitted with Shorter’s propeller. With eight men at the capstan to provide the motive power, she attained a speed of one and a half miles an hour during a calm in Gibraltar Bay and later at Malta.




PATENTED IN 1800, Edward Shorter’s screw propeller was described as a “ perpetual sculling machine”. The screw was submerged in the ship’s wake and was prevented from sinking by a buoy attached to the shaft at the far end. The device was manually operated and tested at a transport event in Doncaster, in 1802. The best speed reached was under two miles an hour.



1804 - Edward Shorter also suggested that his propeller might be driven by a steam-engine, but the first attempt at this method of ship propulsion is credited to an American, Colonel John Stevens, in 1804. Colonel Stevens’ boat was a small twin-screw steam launch. She made a number of successful trial runs in New York Harbour, but these experiments were not crowned with any commercial success.

1832 - Before the patenting of Ericsson’s propeller, inventor - Bennet Woodcroft - had patented a screw with the pitch gradually increasing in a sternward direction. The greater pitch facilitated the attainment of a higher speed.





The original design of the screw propeller patented by Sir Francis Smith is seen on the right. In 1836, the launch F. P. Smith, fitted with this screw, was given a trial on the Paddington Canal, London. At this event half of the screw broke off, whereupon the vessel went considerably faster. The inventor then devised the screw with a single turn, as shown on the left above - in effect, a two-bladed propeller.



1836 - Francis Smith, a farmer at Hendon (Middlesex), patented a single-threaded screw propeller with two complete twists resembling part of a large cork-screw. This revolved in a recess at the stern of the ship. Smith conducted his early screw experiments with a clockwork-driven model on a pond.


Francis Smith used models for his early experiments and Ericsson adopted similar measures. He experimented with a model ship in a circular tank, from the centre of which projected a tubular arm. The model was fitted with a propeller driven by a small steam engine. Steam was supplied to the engine through the rotating tubular arm.


So successful was Smith's little boat that a launch of 6 tons burden, named after the inventor, was built at Wapping. The screw, mounted on a horizontal shaft, was driven by bevel gearing through a vertical shaft reaching above the waterline. The motive power was a steam-engine with a cylinder of 6-in bore and 15-in stroke.

FRANCIS SMITH - Francis Smith's launch was tried on the Paddington Canal, where a serendipitous event led to further improvements in ship propulsion. During one of the launch’s trips on the canal, half of the wooden propeller was broken off, and to the surprise of the crew the speed of the craft was immediately increased. A metal screw, consisting of one complete turn instead of two, was then fitted to the F. P. Smith, and she subsequently made some voyages in the Thames estuary from London to Folkestone at a speed of about five and a half knots. His first experiments were at Hendon.






JOHN ERICSSON - The famous engineer from Sweden retired from the Swedish army, settled in England and worked independently of Smith. In 1836 he also patented a screw propeller consisting of two drums on a shaft. Either drum had a series of helical blades round the periphery, and the blades on one drum were inclined in the direction opposite to those on the other drum. An interesting feature of Ericsson’s propeller was the arrangement of the two drums. These were mounted on a common axis, but they revolved in opposite directions. The after drum revolved at a faster speed because it acted in water that had already been set in motion by the forward drum. This arrangement is know as contra-rotating propellers.





The reversed direction of the after drum was intended to counteract losses caused by the rotary motion of the water behind the leading drum. The arrangement of duplex screws was not adhered to in marine practice, because experience indicated that the complication involved did not improve performance. Ericsson himself often made use of a single screw. A survival of twin screws revolving in opposite directions on one shaft is found in modern torpedos. The arrangement is there used to counteract the “torque” or force that would endeavour to turn the torpedo over against the direction of a single propeller’s rotation.




CONTRA ROTATION - A version of this is now used in an improved form for the modern torpedo. This form of screw was the invention of Captain John Ericsson, the famous Swedish engineer. The forward drum, fitted with helical blades, revolved in one direction and the after drum was turned in the opposite direction at a faster speed. Not bad for 1836.



1837 - In this year the screw propeller was successfully applied to ships, and the honour of contributing this important development in marine engineering is shared by Francis Pettit Smith and by Captain John Ericsson, who worked independently.


The first practical test of Ericsson’s propeller was carried out on the Thames. A 45 ft boat, the Francis B. Oyden, was fitted for screw propulsion. She towed the Admiralty barge, with some of the Lords of the Admiralty on board, from Somerset House to Blackwall and back at an average speed of ten knots.


1838 - After other experiments had been carried out, a United States naval officer, Captain R. F. Stockton, arranged for the construction of a vessel 70 feet long by 10 feet beam, with engines driving directly to the propeller shaft. This ship, the Robert F. Stockton, was built at Birkenhead by Laird Bros, in 1838, and attained a speed of thirteen knots with the tide. She crossed the Atlantic under canvas early in 1839 and saw many years service as a tug in New York harbour under the name New Jersey. Ericsson left for the United States later in 1839. There his invention was used in a number of American river steamers and in the U.S. warship Princeton, built in 1842.


1839 - After these experiment where his screw drive broke and increased performance, Smith amended his patent specification and his screw was described as consisting of a single turn or alternatively a double thread with two half-turns. In this manner was evolved the two-bladed screw propeller.

A company was formed to exploit Smith’s amended patents, and in the same year the Archimedes (237 tons) was launched. She was equipped in the first instance with a single-thread screw 7 feet in diameter. This propeller was subsequently replaced by a screw of the two-bladed type, 5 ft 9-in in diameter, turning at 139 revolutions a minute, connected to the engine that made only 26 revolutions a minute via shaft gearing.

The Archimedes attained a speed of nine knots and, in addition to the circumnavigation of the British Isles, she made a voyage to Oporto, in Portugal. These successes proved the suitability of the screw propeller for marine purposes, and Francis Smith was knighted in 1871 for his services to shipping.


1843 - The Earl of Dundonald patented a propeller with the blades inclined aft to prevent any outward flow of water. Other inventors provided concentric ridges on the blades to achieve the same object, and some screws were sickle-shaped.





1845 - The superiority of the screw propeller over the paddle wheel for the propulsion of ocean-going ships was generally accepted by the end of 1845. In April of that year the famous “duel” between H.M.S. Rattler and H.M.S. Alecto took place. The vessels were similar in size and of equal nominal horse-power, but the screw-driven Rattler, when lashed stern to stern with the paddle-sloop Alecto, was able to tow her rival astern at a speed of nearly three knots.

This test, though, is not regarded as conclusive in favour of the screw, because the Rattler’s engines developed 300 indicated horse-power against the Alecto’s 141, in spite of their equality in nominal horse-power. A real pity they did not use identical engines.

The development of the screw propeller was due to many factors apart from efficiency. A screw propeller cost less than a pair of paddle wheels. It was also more convenient to fit in a ship’s hull, as it required no sponsons or paddle boxes that made ships wider.

For the propulsion of warships, the obvious advantages of the screw were fully appreciated, though the Admiralty at first thought this method of propulsion would interfere with steering. Odd, considering that rudders were commonplace. The outstanding advantage of the propeller over paddle wheels for naval use was, however, its comparative immunity from the effects of gunfire. Propellers were generally completely submerged and the motive power was housed below the water line.


1860-66 - A sickle-shaped propeller was patented by Hermann Hirsch.


1870 - A number of ships were fitted with four-bladed screws of this type. Originally the vessels had been equipped with Griffiths screws, and it is said that after the change their speeds were increased by about one knot.






MODERN BRONZE - Today large propellers are cast in bronze, while smaller versions use more exotic alloys. A gearbox to achieve contra-rotation, one shaft inside the other.




AIRSCREWS - Contra-rotating props are the (almost) exclusive realm of powerful engines with very high disk loading. The most recent designs prefer to use more blades and avoid a heavy gearbox, but the efficiency of such props is poorer than that of propellers with lower disk loading and fewer blades. In a way, the efficiency of the eight-bladed propellers of the Hamilton-Sundstrand NP2000 above is similar to that of four two-bladed propellers in sequence, but it is much easier to build with all blades and their pitch mechanism in one hub.

The Antonov An-70 is a medium and long-range four-engine transport aircraft designed in the 1990s. One of the special features of this aircraft is its propulsion with counter-rotating (blue) propellers, the first group comprising 8 blades, the second 6.





In 1826 Ericsson went to London, where he worked mainly on engines and on locomotives and screw propulsion for boats, receiving 14 patents. English railroad builders kept him profitably at work.

Ericsson invented the caloric steam engine that had a fuel/energy conservation that worked well. He became wealthy with this invention. As early as 1854, Ericsson had worked on designs for an ironclad ship.

In 1861 the Confederate Navy was having the hull of the burned U.S.S. Merrimack covered with iron sheets. The first ironclad was being built by the enemy. Ericsson did not trust or like the U.S. Navy, but was convinced by Cornelius Scranton Bushnell to work on an ironclad for them. Ericsson presented drawings of the USS Monitor, a totally unique and novel design of armored ship, which after much controversy was eventually built and finished on March 6, 1862. The ship went from plans to launch in approximately 100 days, an amazing achievement.

On March 8, the Southern ironclad CSS Virginia was wreaking havoc on the Union Blockading Squadron in Virginia. Then, with the appearance of the Monitor, a battle on March 9, 1862 at Hampton Roads, Virginia, ended in a stalemate between the two iron warships, and saved the Northern fleet from defeat. After this, numerous monitors were built, and are believed to have considerably influenced the victory of the Northern states. Although primitive by modern standards, many basic design elements of the Monitor were copied in future warships by other designers.

Ericsson won a prize in 1840 for the best-designed steam fire engine. He adapted twin screw propellers to a vessel, and by 1844 there were 25 such boats on American waters. In 1844 he completed the 1,000-ton iron frigate U.S.S. Princeton, the first screw-propelled warship and the first with engines and boilers underwater, out of firing range.






Where the British Admiralty failed to comprehend the advantages of Ericssons's propeller invention, this led to what should have been a fortunate contact with the American captain Robert Stockton. Stockton had Ericsson design a propeller steamer for him and told him to bring his invention to the United States of America, as it would supposedly be more welcomed in a land of entrepreneurs.


As a result, Ericsson moved to New York in 1839. Stockton's plan was for Ericsson to oversee the development of a new class of frigate with Stockton using his considerable political connections to lubricate the financial wheels. Finally, after the succession to the Presidency by John Tyler, funds were allocated for a new design. Unfortunately they only received funding for a 700-ton sloop instead of a frigate. The sloop eventually became the USS Princeton, named after Stockton's hometown.

The USS Princeton took about three years to complete and was perhaps the most advanced warship of its time. In addition to twin screw propellers, it was originally designed to mount a 12-inch muzzle loading gun on a revolving pedestal. The gun had also been designed by Ericsson and used the hoop construction method to pre-tension the breech, adding to its strength and safely allowing the use of a larger charge. Other innovations on the ship design included a collapsible funnel and an improved recoil system.

The relations between Ericsson and Stockton grew tense over time and, nearing the completion of the ship, Stockton began working to force Ericsson out of the project.


Stockton carefully avoided letting outsiders know that Ericsson was the primary inventor. Stockton attempted to claim as much credit for himself as possible, even designing a second 12-inch gun to be mounted on the Princeton. Unfortunately, not understanding the design of the first gun (originally named "The Orator", renamed by Stockton to "The Oregon"), the second gun was fatally flawed.

When the ship was initially launched it was a tremendous success. On October 20, 1843 the USS Princeton won a speed competition against the paddle-steamer SS Great Western, which had until then been regarded as the fastest steamer afloat.


Unfortunately, during a firing demonstration of Stockton's gun the breech broke, killing the US Secretary of State Abel P. Upshur and the Secretary of the Navy Thomas Gilmer, as well as six others. Stockton attempted to deflect blame onto Ericsson with moderate success despite the fact that Ericsson's gun was sound and it was Stockton's gun that had failed. Stockton also refused to pay Ericsson and, using his political connections, Stockton managed to block the Navy from paying him.


These actions led to Ericsson's deep resentment toward the US Navy. A warning to any inventor, not to trust navies, or work for them. You are likely to end up working for nothing. Always get payments up front from those looking to benefit from your efforts. Military organisations have absolute power to discredit and ruin anyone who gets in their way.


In the end, Ericsson's ironclad warships earned him a special place in Civil War history, despite the unfortunate episode above. A lesson perhaps to naval officials and everyone else to play with a straight bat.




Marine chronometer from HMS Beagle and Charles Darwin


SOLUTIONS - The chronometer was vital to the ability to create charts and safely navigate the world. The first chronometers were invented by a carpenter's son: John Harrison.

A Marine Chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation. When first developed in the 18th century, it was a major technical achievement, as accurate knowledge of the time over a long sea voyage is necessary for navigation, lacking electronic or communications aids. The first true chronometer was the work of one man, John Harrison, spanning 31 years of persistent experimentation and testing that revolutionized ocean navigation, so enabling the Age of Discovery to accelerate.

The Board of Longitude, charged with finding a solution to this navigation problem, failed to recognise when they had found what they were looking for. This is a frequent problem for experts who only want to recognise solutions that fit within their understanding of current knowledge - not accepting anything that does not conform. They would rather deny a solution. The marine world thought otherwise, gratefully accepting these timepieces as essential navigation aids. This included the Royal Navy's Captain James Cook (HMS Endeavour, Discovery & Resolution) and Captain Robert Fitzroy (HMS Beagle) 1763-1779.


This gimbaled Marine Chronometer seen above was one on H.M.S. Beagle during its second voyage (1831-1836) with Charles Darwin onboard. It sailed to the coast of South America, across the South Pacific towards the Galapagos Islands, New Zealand and Australia, in order to help establish a chain of reliable navigational co-ordinates around the globe.








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