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

DSK wrote:
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


G The problem would arise if you were using a single Z-drive unit. As
it was swiveling, it would give a nasty steering component unless you
stopped the prop, first.

otn

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

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

Capt. Neal® wrote:
As a sailor you should be more concerned with trimming sails.

I can do that, too.

DSK

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

DSK wrote:
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.

Well we disagree there. Look at all the boats in your boatyard -what %
do not use electric thrusters? I think electric is the most common
installation on yachts. I've not seen any alternative to electric and
hydraulic. What have you got in mind?


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.


I said that efficiciency is not an issue for a thuster. Now for
reliability, hydraulic are are no worse than electric motors in hostile
(SW) environments (look at what working fishing boats use to retrieve
gear if you want insight to reliability). That reliability is why
hygraulic power is used so much on mega yachts for furling gear, winches
and rams. But think on this: The hydraulic power will certainly be
there on this size yacht so why not use it? There is no reason to throw
money away when such a simple solution presents itself.


Cheers

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

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.


For main prop definitely CPP. I'm not sure I'd want just hub hydraulic
control though. Might be better to have a servo that can be overridden
by human muscles -just in case.

Cheers

Perhaps you did not realize that Doug is a just a motor boat driver now.
He has some sort of motor boat with nasty osmosis problems -he's
posted lots of pictures of it.

Cheers

Capt. Neal® wrote:

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

Crossed purposes I see. I was thinking about the thrusters here. What is
the origin of term "back down" when talking about going astern come from
anyway -I was misled by it into thinking about manouvering with the
thrusters...

Cheers

DSK wrote:

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

Is that to cut the sea grass?

Cheers

Gilligan wrote:

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.

... 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.


Nav wrote:
Well we disagree there. Look at all the boats in your boatyard -what %
do not use electric thrusters?

Ah, I see the problem. You're confused about the subject.

Again.

The discussion is not about aux thrusters, which can be a trivial
fraction of main engine horsepower, but rather the main propulsion itself.

DSK

The net torque is zero, hence changes can occur quickly. The blade
configuration always has metal in the flow for maximum efficiency, no
chopping.

Anyone who knows anything about propellers knows sternwheelers are used to
cut seagrass.

Gilligan




"Nav" wrote in message
...
Is that to cut the sea grass?

Cheers

Gilligan wrote:

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.

Thanks, it figures. I always knew Mr. King was no sailor.

CN


"Nav" wrote in message ...
Perhaps you did not realize that Doug is a just a motor boat driver now.
He has some sort of motor boat with nasty osmosis problems -he's
posted lots of pictures of it.

Cheers

Capt. Neal® wrote:

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

"Joe" wrote in message om...
Capt. Neal® wrote in message ...
I read the original post again and it just
says 150 foot mega yacht so it probably is
a mono-hull. I guess I was mixing it up with
Oz's thread about the big catamaran he just
bid on from the Greeks?

You could still build a nice tunnel drive into
the hull just forward of the rudder. That would
be my plan if I were filthy rich and were building
such a yacht. Actually, I think I would experiment
with a tunnel either side of the keel where it
fits to the hull. It would look somewhat like
a couple of jet engine nacelles on the tail
of a Gulfstream like this one
http://www.controller.com/images/con...e/00905032.jpg
but with smaller tunnels recessed into the keel.



And it would be an effective add on. However on something in the 150
yacht it would be a smart move to have a twin screw system. If
properly set up you can walk your stern left or right without any
thruster assitance just using your wheel walk. For a bow thruster a
simple 120 hp electric thruster would suffice in a tunnel. If money
were truley no issue than Id go all diesel electric including both
main screws and go with cort nozzles and variable pitch props able to
feather flat. Everything would sail by wire off a joy stick with
computer sail trimming, touch screen navigation and control thruout
the vessel.
But 150 foot is just so second class in today maga yacht scene. Id
build in the 225 footer range.

Joe


225 feet is about where steel comes into its own. Any smaller
than that and it's just too heavy for spritely performance.

I would go whole hog and have it made from stainless steel.
After all, the premise is you won the lottery and money is
no object.

CN

"Nav" wrote in message ...
Perhaps you did not realize that Doug is a just a motor boat driver now.

Not just any old "motor boat driver" if you please.

... He has some sort of motor boat with nasty osmosis problems -he's
posted lots of pictures of it.

Our boat has never had osmosis problems. Once again your bitterness &
spite has muddled the facts.


Capt. Neal® wrote:
Thanks, it figures. I always knew Mr. King was no sailor.

Yep. Keep on thinking that!

DSK

DSK wrote:

"Nav" wrote in message
...

Perhaps you did not realize that Doug is a just a motor boat driver now.


Not just any old "motor boat driver" if you please.

... He has some sort of motor boat with nasty osmosis problems -he's
posted lots of pictures of it.


Our boat has never had osmosis problems. Once again your bitterness &
spite has muddled the facts.


Your motor boat did not have blisters along the water line? Whose boat
was it?

Cheers

Capt. Neal® wrote:

"Joe" wrote in message om...

Capt. Neal® wrote in message ...

I read the original post again and it just
says 150 foot mega yacht so it probably is
a mono-hull. I guess I was mixing it up with
Oz's thread about the big catamaran he just
bid on from the Greeks?

You could still build a nice tunnel drive into
the hull just forward of the rudder. That would
be my plan if I were filthy rich and were building
such a yacht. Actually, I think I would experiment
with a tunnel either side of the keel where it
fits to the hull. It would look somewhat like
a couple of jet engine nacelles on the tail
of a Gulfstream like this one
http://www.controller.com/images/con...e/00905032.jpg
but with smaller tunnels recessed into the keel.



And it would be an effective add on. However on something in the 150
yacht it would be a smart move to have a twin screw system. If
properly set up you can walk your stern left or right without any
thruster assitance just using your wheel walk. For a bow thruster a
simple 120 hp electric thruster would suffice in a tunnel. If money
were truley no issue than Id go all diesel electric including both
main screws and go with cort nozzles and variable pitch props able to
feather flat. Everything would sail by wire off a joy stick with
computer sail trimming, touch screen navigation and control thruout
the vessel.
But 150 foot is just so second class in today maga yacht scene. Id
build in the 225 footer range.

Joe



225 feet is about where steel comes into its own. Any smaller
than that and it's just too heavy for spritely performance.

I would go whole hog and have it made from stainless steel.
After all, the premise is you won the lottery and money is
no object.


Stainless steel is not a cure all for corrosion problems -it's also
heavy for a yacht. Aluminum seems a more common solution.

Cheers

"Nav" wrote in message
...


Capt. Neal® wrote:

"Joe" wrote in message
om...

Capt. Neal® wrote in message
...

I read the original post again and it just
says 150 foot mega yacht so it probably is
a mono-hull. I guess I was mixing it up with
Oz's thread about the big catamaran he just
bid on from the Greeks?

You could still build a nice tunnel drive into
the hull just forward of the rudder. That would
be my plan if I were filthy rich and were building
such a yacht. Actually, I think I would experiment
with a tunnel either side of the keel where it
fits to the hull. It would look somewhat like
a couple of jet engine nacelles on the tail
of a Gulfstream like this one
http://www.controller.com/images/con...e/00905032.jpg
but with smaller tunnels recessed into the keel.



And it would be an effective add on. However on something in the 150
yacht it would be a smart move to have a twin screw system. If
properly set up you can walk your stern left or right without any
thruster assitance just using your wheel walk. For a bow thruster a
simple 120 hp electric thruster would suffice in a tunnel. If money
were truley no issue than Id go all diesel electric including both
main screws and go with cort nozzles and variable pitch props able to
feather flat. Everything would sail by wire off a joy stick with
computer sail trimming, touch screen navigation and control thruout
the vessel.
But 150 foot is just so second class in today maga yacht scene. Id
build in the 225 footer range.

Joe



225 feet is about where steel comes into its own. Any smaller
than that and it's just too heavy for spritely performance.

I would go whole hog and have it made from stainless steel.
After all, the premise is you won the lottery and money is
no object.


Stainless steel is not a cure all for corrosion problems -it's also heavy
for a yacht. Aluminum seems a more common solution.

Cheers

What? No Titanium?
Scout

Aluminum is relatively worthless for a boat hull.

All it takes to completely destroy the hull of an
aluminum hulled vessel is a handful of mercury
past smeared on it. It will begin to turn to dust within
hours, break apart and sink.

A stainless steel boat is impervious to just about
anything but strong acids.

CN



"Nav" wrote in message ...


Capt. Neal® wrote:

"Joe" wrote in message om...

Capt. Neal® wrote in message ...

I read the original post again and it just
says 150 foot mega yacht so it probably is
a mono-hull. I guess I was mixing it up with
Oz's thread about the big catamaran he just
bid on from the Greeks?

You could still build a nice tunnel drive into
the hull just forward of the rudder. That would
be my plan if I were filthy rich and were building
such a yacht. Actually, I think I would experiment
with a tunnel either side of the keel where it
fits to the hull. It would look somewhat like
a couple of jet engine nacelles on the tail
of a Gulfstream like this one
http://www.controller.com/images/con...e/00905032.jpg
but with smaller tunnels recessed into the keel.



And it would be an effective add on. However on something in the 150
yacht it would be a smart move to have a twin screw system. If
properly set up you can walk your stern left or right without any
thruster assitance just using your wheel walk. For a bow thruster a
simple 120 hp electric thruster would suffice in a tunnel. If money
were truley no issue than Id go all diesel electric including both
main screws and go with cort nozzles and variable pitch props able to
feather flat. Everything would sail by wire off a joy stick with
computer sail trimming, touch screen navigation and control thruout
the vessel.
But 150 foot is just so second class in today maga yacht scene. Id
build in the 225 footer range.

Joe



225 feet is about where steel comes into its own. Any smaller
than that and it's just too heavy for spritely performance.

I would go whole hog and have it made from stainless steel.
After all, the premise is you won the lottery and money is
no object.


Stainless steel is not a cure all for corrosion problems -it's also
heavy for a yacht. Aluminum seems a more common solution.

Cheers

a rogue tuna?
Scout

"Capt. Neal®" wrote
All it takes to completely destroy the hull of an
aluminum hulled vessel is a handful of mercury
past smeared on it.

Scout wrote:

"Nav" wrote in message
...


Capt. Neal® wrote:


"Joe" wrote in message
e.com...


Capt. Neal® wrote in message
...


I read the original post again and it just
says 150 foot mega yacht so it probably is
a mono-hull. I guess I was mixing it up with
Oz's thread about the big catamaran he just
bid on from the Greeks?

You could still build a nice tunnel drive into
the hull just forward of the rudder. That would
be my plan if I were filthy rich and were building
such a yacht. Actually, I think I would experiment
with a tunnel either side of the keel where it
fits to the hull. It would look somewhat like
a couple of jet engine nacelles on the tail
of a Gulfstream like this one
http://www.controller.com/images/con...e/00905032.jpg
but with smaller tunnels recessed into the keel.



And it would be an effective add on. However on something in the 150
yacht it would be a smart move to have a twin screw system. If
properly set up you can walk your stern left or right without any
thruster assitance just using your wheel walk. For a bow thruster a
simple 120 hp electric thruster would suffice in a tunnel. If money
were truley no issue than Id go all diesel electric including both
main screws and go with cort nozzles and variable pitch props able to
feather flat. Everything would sail by wire off a joy stick with
computer sail trimming, touch screen navigation and control thruout
the vessel.
But 150 foot is just so second class in today maga yacht scene. Id
build in the 225 footer range.

Joe



225 feet is about where steel comes into its own. Any smaller
than that and it's just too heavy for spritely performance.

I would go whole hog and have it made from stainless steel.
After all, the premise is you won the lottery and money is
no object.


Stainless steel is not a cure all for corrosion problems -it's also heavy
for a yacht. Aluminum seems a more common solution.

Cheers


What? No Titanium?

Terrible metal for a yacht -lack of ductility. Gold alloy might be better.

Cheers

"Nav" wrote in message
...


Scout wrote:

"Nav" wrote in message
...


Capt. Neal® wrote:


"Joe" wrote in message
le.com...


Capt. Neal® wrote in message
...


I read the original post again and it just
says 150 foot mega yacht so it probably is
a mono-hull. I guess I was mixing it up with
Oz's thread about the big catamaran he just
bid on from the Greeks?

You could still build a nice tunnel drive into
the hull just forward of the rudder. That would
be my plan if I were filthy rich and were building
such a yacht. Actually, I think I would experiment
with a tunnel either side of the keel where it
fits to the hull. It would look somewhat like
a couple of jet engine nacelles on the tail
of a Gulfstream like this one
http://www.controller.com/images/con...e/00905032.jpg
but with smaller tunnels recessed into the keel.



And it would be an effective add on. However on something in the 150
yacht it would be a smart move to have a twin screw system. If
properly set up you can walk your stern left or right without any
thruster assitance just using your wheel walk. For a bow thruster a
simple 120 hp electric thruster would suffice in a tunnel. If money
were truley no issue than Id go all diesel electric including both
main screws and go with cort nozzles and variable pitch props able to
feather flat. Everything would sail by wire off a joy stick with
computer sail trimming, touch screen navigation and control thruout
the vessel.
But 150 foot is just so second class in today maga yacht scene. Id
build in the 225 footer range.

Joe



225 feet is about where steel comes into its own. Any smaller
than that and it's just too heavy for spritely performance.

I would go whole hog and have it made from stainless steel.
After all, the premise is you won the lottery and money is
no object.


Stainless steel is not a cure all for corrosion problems -it's also heavy
for a yacht. Aluminum seems a more common solution.

Cheers


What? No Titanium?

Terrible metal for a yacht -lack of ductility. Gold alloy might be better.

Cheers

pure gold is too dense?
Scout

A whole school of tuna hitting the hull might do it . . .

CN


"Scout" wrote in message ...
a rogue tuna?
Scout

"Capt. Neal®" wrote
All it takes to completely destroy the hull of an
aluminum hulled vessel is a handful of mercury
past smeared on it.

In article ,
=?Windows-1252?Q?Capt._Neal=AE?= wrote:
A whole school of tuna hitting the hull might do it . . .

CN

In your case, one guppy would sink your boat.

--
Jonathan Ganz (j gan z @ $ail no w.c=o=m)
http://www.sailnow.com
"If there's no wind, row."

Capt. Neal® wrote:

Aluminum is relatively worthless for a boat hull.

All it takes to completely destroy the hull of an
aluminum hulled vessel is a handful of mercury
past smeared on it. It will begin to turn to dust within
hours, break apart and sink.


Hahahha. A handful of mercury?


A stainless steel boat is impervious to just about
anything but strong acids.


How about salt water and time?

Cheers

Scout wrote:

"Nav" wrote in message
...


Scout wrote:


"Nav" wrote in message
...


Capt. Neal® wrote:



"Joe" wrote in message
gle.com...



Capt. Neal® wrote in message
...



I read the original post again and it just
says 150 foot mega yacht so it probably is
a mono-hull. I guess I was mixing it up with
Oz's thread about the big catamaran he just
bid on from the Greeks?

You could still build a nice tunnel drive into
the hull just forward of the rudder. That would
be my plan if I were filthy rich and were building
such a yacht. Actually, I think I would experiment
with a tunnel either side of the keel where it
fits to the hull. It would look somewhat like
a couple of jet engine nacelles on the tail
of a Gulfstream like this one
http://www.controller.com/images/con...e/00905032.jpg
but with smaller tunnels recessed into the keel.



And it would be an effective add on. However on something in the 150
yacht it would be a smart move to have a twin screw system. If
properly set up you can walk your stern left or right without any
thruster assitance just using your wheel walk. For a bow thruster a
simple 120 hp electric thruster would suffice in a tunnel. If money
were truley no issue than Id go all diesel electric including both
main screws and go with cort nozzles and variable pitch props able to
feather flat. Everything would sail by wire off a joy stick with
computer sail trimming, touch screen navigation and control thruout
the vessel.
But 150 foot is just so second class in today maga yacht scene. Id
build in the 225 footer range.

Joe



225 feet is about where steel comes into its own. Any smaller
than that and it's just too heavy for spritely performance.

I would go whole hog and have it made from stainless steel.
After all, the premise is you won the lottery and money is
no object.


Stainless steel is not a cure all for corrosion problems -it's also heavy
for a yacht. Aluminum seems a more common solution.

Cheers


What? No Titanium?

Terrible metal for a yacht -lack of ductility. Gold alloy might be better.

Cheers


pure gold is too dense?
Scout

Too soft.

Cheers

I said mercury paste. Mercury at room temp is a liquid and
difficult to hold in the palm of one's hand while mercury
paste is similar to paste wax and can be held and smeared
on by hand.


"Nav" wrote in message ...


Capt. Neal® wrote:

Aluminum is relatively worthless for a boat hull.

All it takes to completely destroy the hull of an
aluminum hulled vessel is a handful of mercury
past smeared on it. It will begin to turn to dust within
hours, break apart and sink.


Hahahha. A handful of mercury?


A stainless steel boat is impervious to just about
anything but strong acids.


How about salt water and time?

Cheers