Seamanship Question #16 [Props again]
 

2 points

After hitting the lottery for big bucks, you have nearly completed
your 150' new sailing mega yacht. Included on your new toy are both a
bow and stern thrusters--for side-to-side control..

What sort of prop would you want if you were concerned about precise
speed control, and being able to back down nearly instantaneously?

Money is, of course not a concern.

Bart Senior wrote:
2 points

After hitting the lottery for big bucks, you have nearly completed
your 150' new sailing mega yacht. Included on your new toy are both a
bow and stern thrusters--for side-to-side control..

What sort of prop would you want if you were concerned about precise
speed control, and being able to back down nearly instantaneously?

Money is, of course not a concern.

Hydraulically controlled variable pitch.

BTW is this 150' yacht equipped with a rack of racing dinghies and a
retractable artificial beach?

Fresh Breezes- Doug King

Bart Senior wrote:
2 points

After hitting the lottery for big bucks, you have nearly completed
your 150' new sailing mega yacht. Included on your new toy are both a
bow and stern thrusters--for side-to-side control..

What sort of prop would you want if you were concerned about precise
speed control, and being able to back down nearly instantaneously?

Money is, of course not a concern.




G Z-drive ..... course, then you wouldn't need the stern thruster

Counter rotating scythe propellers with electric drive.

Gilligan

"Bart Senior" wrote in message
...
2 points

After hitting the lottery for big bucks, you have nearly completed
your 150' new sailing mega yacht. Included on your new toy are both a
bow and stern thrusters--for side-to-side control..

What sort of prop would you want if you were concerned about precise
speed control, and being able to back down nearly instantaneously?

Money is, of course not a concern.

I would go for a big, honkin', fixed, six-bladed prop in a tunnel,
designed as a system and driven by hydraulics. A streamlined
door on each end of the drive could be closed when under sail
to minimize drag.

For maximum thrust in reverse without a tendency to side slip
one needs tunnel drive. It works for most of the big tugs on
the Western Rivers it should do the job on a relatively lightweight
yacht.

CN


"Bart Senior" wrote in message ...
2 points

After hitting the lottery for big bucks, you have nearly completed
your 150' new sailing mega yacht. Included on your new toy are both a
bow and stern thrusters--for side-to-side control..

What sort of prop would you want if you were concerned about precise
speed control, and being able to back down nearly instantaneously?

Money is, of course not a concern.

He asked what kind of prop - not props. Pay attention,
little buddy.

CN

"Gilligan" wrote in message nk.net...
Counter rotating scythe propellers with electric drive.

Gilligan

"Bart Senior" wrote in message
...
2 points

After hitting the lottery for big bucks, you have nearly completed
your 150' new sailing mega yacht. Included on your new toy are both a
bow and stern thrusters--for side-to-side control..

What sort of prop would you want if you were concerned about precise
speed control, and being able to back down nearly instantaneously?

Money is, of course not a concern.

Capt. Neal® wrote:
I would go for a big, honkin', fixed, six-bladed prop in a tunnel,
designed as a system and driven by hydraulics. A streamlined
door on each end of the drive could be closed when under sail
to minimize drag.

For maximum thrust in reverse without a tendency to side slip
one needs tunnel drive. It works for most of the big tugs on
the Western Rivers it should do the job on a relatively lightweight
yacht.

CN

I think you'll find that what most tugs use are Kort Nozzles, rather
than tunnel drive. The idea being to improve bollard pull, rather than
reduce prop walk (prop walk is your friend if you know how to use it).

otn

2 points to you Doug!

And if it was up to me, I'd at least want a a fold down
dock on the back for those dinghies.

DSK wrote

Bart Senior wrote:
2 points

After hitting the lottery for big bucks, you have nearly completed
your 150' new sailing mega yacht. Included on your new toy are both a
bow and stern thrusters--for side-to-side control..

What sort of prop would you want if you were concerned about precise
speed control, and being able to back down nearly instantaneously?

Money is, of course not a concern.

Hydraulically controlled variable pitch.

BTW is this 150' yacht equipped with a rack of racing dinghies and a
retractable artificial beach?

Fresh Breezes- Doug King

Capt. Neal® wrote:


I think they are talking of a big catamaran which makes
it an entirely different animal. Little or no heeling and the
ability to travel at high speeds. Nice little transoms
available for twin tunnel drives. The ability to raise
the drives for beaching without fear of damaging the
props. Seems ideal to me. More efficiency in reverse
because of the tunnels which was the original desired
trait.

It looks to me, though, that a Kort nozzle would be
more efficient in reverse because of the more symmetrical
shape of the prop blades.

CN

It's a "general" rule that boats with Korts tend to lose some backing
efficiency over their un-Korted brothers .....couldn't explain why
(whether it's the shape of the nozzle or design of the prop, or both)

otn

otnmbrd wrote:
It's a "general" rule that boats with Korts tend to lose some backing
efficiency over their un-Korted brothers .....couldn't explain why
(whether it's the shape of the nozzle or design of the prop, or both)

Probably the nozzle- you could make the nozzle symmetrical, but it would
cost some efficiency in forward motion. The question is would it still
be more efficient than an un-nozzled prop.

A Z-drive or Azipod would be cool... no such thing as reverse, it's
always in forward! Just swivel the whole thing around just like a video
game.

Fresh Breezes- Doug King