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

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

There's no need for variable pitch -which is why you don't see it in
mega yacht thrusters


Cheers FT.

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

Nav wrote:
There's no need for variable pitch -which is why you don't see it in
mega yacht thrusters


Cheers FT.

I believe the discussion regarded the Main Engine, not the thrusters

otnmbrd wrote:

Nav wrote:

There's no need for variable pitch -which is why you don't see it in
mega yacht thrusters


Cheers FT.


I believe the discussion regarded the Main Engine, not the thrusters

I thought it was 'bout the whole propulksion package 'cos he mentioned
dual thrusters. If just about main engine that's a really boring question.

Cheers

The larger the vessel the more difficult it is to
manuever and stop.

I wanted to be clear the issue in this question
was with respect to backing down. The thrustors
provide good side-to-side control and eliminate
that factor from the question. Could it have
be written more clearly?

The variable pitch allows the throttle to be
set and forgotten while pitch controls linear
thrust--magnitude and direction.

There are no worries about engine stalling while
changing gears, or cables jamming or snapping,
all of which have happened to me in the past, and
each of which could be bad news docking and
manuevering a mega yacht.

Bart Senior


Nav wrote
otnmbrd wrote:

Nav wrote:

There's no need for variable pitch -which is why you don't see it in
mega yacht thrusters


Cheers FT.


I believe the discussion regarded the Main Engine, not the thrusters

I thought it was 'bout the whole propulksion package 'cos he mentioned
dual thrusters. If just about main engine that's a really boring question.

Cheers

Doug,

There's no need for the complication of variable pitch. A reversing
motor (electric or hydraulic) is all that is needed. Hence for this
size vessel you see symmetric 4 blade props. The small increase in
efficiency gained by having variable pitch is not worth the extra
complication.

Cheers


DSK wrote in message ...
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

Farr1220 wrote:
Doug,

There's no need for the complication of variable pitch.

Well, sure. There's no "need" for the boat at all.

... A reversing
motor (electric or hydraulic) is all that is needed.

And that's simpler than a CPP?

... Hence for this
size vessel you see symmetric 4 blade props.

Sometimes 5 blade.

... The small increase in
efficiency gained by having variable pitch is not worth the extra
complication.

Bart wasn't asking about efficiency, he was asking about
controllability. An electric drive may be on par with the controlled
pitch for quick & easy reversing, but they're much less common... the
ones I know about have a bad reputation for being troublesome.

As for a hydraulic motor, if you think these are efficient and
trouble-free then I suggest you get some experience with them. It would
be at the bottom of my list for almost any power application.

Actually CPPs are slightly less efficient, ideally, than conventional
props becuase of the bulky hubs. However, in real world conditions, they
often achieve greater efficiency by being able to trim the prop to match
sea/wind conditions to engine load.

Fresh Breezes- Doug King

As a sailor you should be more concerned with trimming sails.

Leave the motors to the likes of Captains Shen and otn.

Captain Neal
(a member of an elite group)

"DSK" wrote in message ...
Farr1220 wrote:
Doug,

There's no need for the complication of variable pitch.

Well, sure. There's no "need" for the boat at all.

... A reversing
motor (electric or hydraulic) is all that is needed.

And that's simpler than a CPP?

... Hence for this
size vessel you see symmetric 4 blade props.

Sometimes 5 blade.

... The small increase in
efficiency gained by having variable pitch is not worth the extra
complication.

Bart wasn't asking about efficiency, he was asking about
controllability. An electric drive may be on par with the controlled
pitch for quick & easy reversing, but they're much less common... the
ones I know about have a bad reputation for being troublesome.

As for a hydraulic motor, if you think these are efficient and
trouble-free then I suggest you get some experience with them. It would
be at the bottom of my list for almost any power application.

Actually CPPs are slightly less efficient, ideally, than conventional
props becuase of the bulky hubs. However, in real world conditions, they
often achieve greater efficiency by being able to trim the prop to match
sea/wind conditions to engine load.

Fresh Breezes- Doug King