A fish could be up to 90% efficient while a screw propeller
fish robot is at most 50% efficient .
The flow produced by the screw propeller
and caused by the effect of the stern screw of the propeller usually is not taken into account in many cases; however, this effect could have a considerable influence on the force of tug pulling.
The principles underlying this kind of propulsion are different from those for a conventional screw propeller
. To better understand how these animals swim, Licht designed Finnegan with four flapping foils.
His revolutionary iron ship, Great Britain, of 1843, the first major ship powered by a screw propeller
sailed from Liverpool to the US and carried a total of 15,000 emigrants to Australia.
By 1900, numerous books on screw propeller
design had been published.
He took after his father in having a flair for machinery and in his twenties he invented a screw propeller
for ships, only to find that someone else had invented it just before him.
Although the steamship was first developed early in the 19th century, further innovations in subsequent decades--the screw propeller
, steel hulls, the compound engine--transformed what had been primarily a river vessel into cheap and reliable ocean transport.
In 1827, however, a British engineer, Robert Wilson (1803-1882), designed a screw propeller
, which worked from the stern of the ship, so that it was symmetrically placed and was little affected by the ship's rolling.
1 She was the first ship to have a screw propeller
, an iron hull and a massive 1,000 horsepower steam engine
The choice of an optimum ship screw propeller
is a persistent problem in naval architecture.