On Thu, 25 Dec 2008 10:28:16 -0500, Boater wrote:

Eisboch wrote:
"Boater" wrote in message
...


Technology and innovation

* David Bushnell (ca. 1776), inventor of the screw propeller,
submarine, naval mine, and time bomb.


Being boating related, I thought I'd mention that there are several claims
to have "invented" the screw propeller.

Bushnell isn't even mentioned at this site:

http://www.irvineayrshire.org/propeller.htm


Eisboch (Ho, ho, ho!)





There's more than one way to screw.

Here's a wiki entry:

David Bushnell (1742 - 1824) of Saybrook, Connecticut, was an American
inventor during the Revolutionary War. He is credited with creating the
first submarine ever used in combat, while studying at Yale University
in 1775. He called it the Turtle because of its look in the water. His
idea of using water as ballast for submerging and raising his submarine
is still in use today, as is the screw propeller, which was first used
in the Turtle.

While at Yale, he proved that gunpowder exploded under water. David
Bushnell also made the first time bomb. With this, he also came up with
mine barrage in 1777. He also invented the first time bomb. He combined
his ideas in an attempt to attack British ships which were blockading
New York Harbor in the summer of 1776 by boring through their hulls and
implanting time bombs, but failed every time due to a metal lining in
the ships hull to protect against parasites in their previous station,
the Caribbean. David Bushnell then created the Turtle. The Turtle
eventually sank.

On June 8, 1781 he was promoted Captain of Sappers and Miners. Bushnell
later traveled to France and then settled in Warrenton, Georgia where he
taught at the Warrenton Academy and practiced medicine. He died in 1824,
but before he died David was honored with a medal by George Washington.
David Bushnell's Submarine Model is on display at the U.S. Navy
Submarine Force Museum and Library in Groton, Connecticut.


Another wiki:

H
James Watt of Scotland is generally credited with applying the first
screw propeller to an engine, an early steam engine, beginning the use
of an hydrodynamic screw for propulsion.

Mechanical ship propulsion began with the steam ship. The first
successful ship of this type is a matter of debate; candidate inventors
of the 18th century include William Symington, the Marquis de Jouffroy,
John Fitch and Robert Fulton, however William Symington's ship the
Charlotte Dundas is regarded as the world's "first practical steamboat".
Paddlewheels as the main motive source became standard on these early
vessels (see Paddle steamer). Robert Fulton had tested, and rejected,
the screw propeller.
Sketch of hand-cranked vertical and horizontal screws used in Bushnell's
Turtle, 1775

The screw (as opposed to paddlewheels) 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. The first screw propeller to be powered by a gasoline
engine, fitted to a small boat (now known as a powerboat) was installed
by Frederick Lanchester, also from Birmingham. This was tested in
Oxford. The first 'real-world' use of a propeller was by David Bushnell,
who used hand-powered screw propellers to navigate his submarine
"Turtle" in 1776. The Bohemian engineer Josef Ressel designed and
patented the first practicable 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)
Voith-Schneider propeller

Initial designs owed much to the ordinary screw from which their name
derived - early propellers consisted of only two blades and matched in
profile the length of a single screw rotation. This design was common,
but inventors endlessly experimented with different profiles and greater
numbers of blades. The propeller screw design stabilized by the 1880s.

In the early days of steam power for ships, when both paddle wheels and
screws were in use, ships were often characterized by their type of
propellers, leading to terms like screw steamer or screw sloop.

Harry, did you check to see who entered the Wikipedia entries. It could
well have been another 'Yale graduate' such as yourself.
--
John

Have a Super Christmas and a Spectacular New Year!