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Thanks, Marc,
I knew "oar" wasn't the right term, but it was the best I could come up
with at the time. It's amazing to see those guys propel a sizable boat and
even back up using a yuloh. I had never heard the term.
In my design I'm trying to eliminate the possibility of snagging on
something as much as possible, and a Kort is part of that. Also, sharp
things spinning around scare me as they can be rough on divers, manatees,
etc. I plan to have a removable guard on the intake side so I can operate
with or without it depending on the situation.
Jim
In a message dated 11/20/2010 12:41:50 A.M. Central Standard Time,
piolenc@archivale.com writes:
On
11/20/2010 1:29 PM, JimToddPsub@aol.com wrote:
> As you mentioned, a
larger diameter prop is somewhat more efficient than
> a smaller one.
The problem is that it bumps into things and otherwise
> gets in the
way.
Which brings up another motive for using a shrouded propeller
(Kort
nozzle), namely that the effective diameter of the propeller can be
larger than its physical diameter, thanks to the stream tube distortion
caused by the shroud. In machinery operating in air, it can allow higher
propeller rpm without worrying about compressibility effects at the tip.
In submersibles it's just...convenient.
> You may have seen
boats used in the orient that are propelled by a long,
> hinged oar that
is wagged back and forth at the rear of the boat much
> like a fish
tail. Sorry I don't know what it's called. The oarsman is
> standing and
the boat rocks back and forth with each stroke. I've only
> seen them in
National Geographic type films. Maybe someone has eyes-on
>
experience.
I think that special oar (or scull, rather) is called a
yuloh.
Marc de Piolenc
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