On Mon, 9 Nov 2009 11:39:07 -0800 (PST),
wrote:

Ron Wanttaja wrote:
Years ago, when there was a controversy as to whether paddles or
propellers were most efficient for ships, the British came up with a
simple test: They built two identical ships, with identical engines,
one with paddles and one with a prop. They tied a rope between the
sterns, and had the captains go to full power to see which had more
thrust.

Wikipedia says that "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 2.5 knots (4.6 km/h)...."

http://en.wikipedia.org/wiki/Propeller

Jim Logajan wrote:

However, it is probable that the paddle wheel ship simply didn't have the
right size paddles. Paddle wheels should be capable of efficiencies similar
to propellers - but it takes very large wheels.

I used to think so, too, but an article a couple of years ago in
Flying, by Peter Garrison, set me straight. It was about Lift to Drag
ratios and Coefficients of Lift, and laid out what those mean not
only in terms of wings, but any foil, including propellers. A
paddlewheel cannot generate any more thrust than the torque applied to
its shaft can produce at the arm-length of the paddle, while a
propeller can produce more thrust because its blades can cut through
the medium with a minimum of effort and produce considerably more lift
or thrust for a given torque than a paddle will.

So we don't see paddlewheels on boats anymore.

I wish I could find Garrison's article again.

Dan

paddle wheels still exist in australia. the murray river runs through
the old paddle steamer inland port of echuca in victoria where there
are quite a few paddle steamers that still run for the tourist trade
these days.
worth a visit and a day spent on the boats if you are ever in the
area.
australia's paddlesteamers developed as a separate technology from the
american sternwheelers. ours are side wheelers due to the winding
nature of the murray.

a proper australian sidewheeler is based on the rule of thirds.
the paddles are a third of the diameter wide and the paddle boards are
a third of the width deep. that's what works best.

www.murrayriver.com.au/paddleboats
www.emmylou.com.au
http://www.echuca.ws/...Paddlesteame...esteamers.html
that'll get you started.

I find this particular vintage history fascinating.

connection with flying? none! I wasnt flying the time I spent my day
on the boats. one of the few days I havent wished I was flying.
Stealth Pilot