On Nov 22, 6:39*pm, Bruce wrote:
On Mon, 22 Nov 2010 08:54:03 -0800 (PST), Joe





wrote:
On Nov 22, 9:40 am, Wayne.B wrote:
On Mon, 22 Nov 2010 07:21:00 -0800 (PST), Joe

wrote:
Now directly couple a motor/generator that consists of a stator
winding employing a high pole count configuration, which allows for
high copper utilization (minimizing energy loss and cost), and a
hollow rotor upon which powerful rare earth permanent magnets are
mounted on the outer circumference coupled to a variable pitch prop
system and you can pump out some serious energy. The city buses that
are using these moters claim they capture 97% of the kinetic energy
developed while stopping.

Regardless of the capture mechanism, even at 100% efficiency, there is
only so much energy in a moving column of water and it is not a big
number when you are moving at sailing speeds. Now if you could get
that same column of water rolling down the side of a 1,000 ft
mountain, that's a whole different story. :-)

*I'm going to have to disagree with you Wayne. The amount of energy
coming off a shaft at sailing speed can be huge. The drag can be
offset by canvas with ease on a non-planing hull. If you capture 1 rpm
of energy for every 4 rmp's generated by sail, and can store that
energy you have a system that can work.

Now if a bus can capture 97% of the kinetic energy by stopping then
why can't a prop do the same ?
About the smallest CVP system available is in the high 30's low 40"
diameter.
You ever chain down a shaft to a 40" prop? You better have some strong
chain.

http://www.youtube.com/watch?v=6KSnH6DFA94*Not quite a 1000 ft drop
but plenty of power to harness.

Joe

Are you normally obtuse, or have you always gotten your technical
information from the movies?

The Youtube show you recommended states that it is a 200 ton sailing
boat. While your reference doesn't indicate the length of the vessel
but seems to say that they were doing 9 knots.

I found a reference to another 200 ton sailing vessel on the net - it
was 138 feet long. The hull speed for a 138 ft. vessel is about 16
knots so your reference was sailing at abut half hull speed (56%
actually). Hardly impressive.


Hardly, but enough to spin a big prop without much concern of the drag
the prop makes..

And, by the bay, how many sailing yachts have you been on that were
fitted with a 40 inch propeller?

None by the bay;0). Never been on with a CVP propellor, or cort
nozzles either. Never been on one with a bow thruster , or forward
looking sonar, or a kite drive either. Never been on a hydrofoil
bigger than a rave...but there are ones out there.

Have been on a hundred boats with 25-72 inch props and had to chain
them down many times to prevent damage to the gears. As I said the
power is massive and you had better have heavy chains and binders.

Joe


Cheers,

Brice- Hide quoted text -

- Show quoted text -

On Mon, 22 Nov 2010 17:49:24 -0800 (PST), Joe
wrote:

Have been on a hundred boats with 25-72 inch props and had to chain
them down many times to prevent damage to the gears. As I said the
power is massive and you had better have heavy chains and binders.

Joe, my trawler has 30 inch, 4 bladed props on 2 1/2 shafts. Can you
suggest a procedure for safely binding/chaining a shaft while
underway? I was thinking about something like 3 or 4 loops of 1 inch
line terminating in a block and tackle lead to an overhead beam.

On Mon, 22 Nov 2010 21:37:09 -0500, Wayne.B
wrote:

On Mon, 22 Nov 2010 17:49:24 -0800 (PST), Joe
wrote:

Have been on a hundred boats with 25-72 inch props and had to chain
them down many times to prevent damage to the gears. As I said the
power is massive and you had better have heavy chains and binders.

Joe, my trawler has 30 inch, 4 bladed props on 2 1/2 shafts. Can you
suggest a procedure for safely binding/chaining a shaft while
underway? I was thinking about something like 3 or 4 loops of 1 inch
line terminating in a block and tackle lead to an overhead beam.

If you are serious the usual method is to install a shaft brake.
Mechanical or hydraulic disk brake.

Cheers,

Brice

On Mon, 22 Nov 2010 21:37:09 -0500, Wayne.B
wrote:

On Mon, 22 Nov 2010 17:49:24 -0800 (PST), Joe
wrote:

Have been on a hundred boats with 25-72 inch props and had to chain
them down many times to prevent damage to the gears. As I said the
power is massive and you had better have heavy chains and binders.

Joe, my trawler has 30 inch, 4 bladed props on 2 1/2 shafts. Can you
suggest a procedure for safely binding/chaining a shaft while
underway? I was thinking about something like 3 or 4 loops of 1 inch
line terminating in a block and tackle lead to an overhead beam.


Out of curiosity, why chain the shaft? Are you running on one engine?
And, if you are how is it working for you. I tried it and it simply
dropped the speed by about half :-(

Cheers,

Brice

On Tue, 23 Nov 2010 17:46:50 +0700, Bruce
wrote:

Out of curiosity, why chain the shaft? Are you running on one engine?
And, if you are how is it working for you. I tried it and it simply
dropped the speed by about half :-(

On our boat we can improve fuel efficiency by about 25% running on a
single engine assuming a speed of no more than about 1.1 SQRT LWL.

We have Detroit 6-71 2-cycle diesels which are not efficient at low
speeds. Running single engine gets operating RPMs up to a normal
level. This is useful on long passages in relatively light winds and
calm seas. If the wind kicks up we need more power to maintain speed
and stability.

On Tue, 23 Nov 2010 06:15:07 -0500, Wayne.B
wrote:

On Tue, 23 Nov 2010 17:46:50 +0700, Bruce
wrote:

Out of curiosity, why chain the shaft? Are you running on one engine?
And, if you are how is it working for you. I tried it and it simply
dropped the speed by about half :-(

On our boat we can improve fuel efficiency by about 25% running on a
single engine assuming a speed of no more than about 1.1 SQRT LWL.

We have Detroit 6-71 2-cycle diesels which are not efficient at low
speeds. Running single engine gets operating RPMs up to a normal
level. This is useful on long passages in relatively light winds and
calm seas. If the wind kicks up we need more power to maintain speed
and stability.

I've got littler engines and at cruise are running about 2,000 RPM on
both. Cutting one engine reduces speed by about half.

But you have, I believe a Grand Banks, which has a semi-planeing hull,
I think the company calls it, that can benefit from larger engines. My
boat is a displacement hull so additional H.P. isn't going to make a
vast difference.

You say "maintain speed and stability", do you have active
stabilizers?

Cheers,

Brice

On Wed, 24 Nov 2010 07:37:46 +0700, Bruce
wrote:

You say "maintain speed and stability", do you have active
stabilizers?

Yes, Naiads.

http://www.naiad.com/Product_Flyer_162-302.pdf

On Tue, 23 Nov 2010 06:15:07 -0500, Wayne.B
wrote:

On Tue, 23 Nov 2010 17:46:50 +0700, Bruce
wrote:

Out of curiosity, why chain the shaft? Are you running on one engine?
And, if you are how is it working for you. I tried it and it simply
dropped the speed by about half :-(

On our boat we can improve fuel efficiency by about 25% running on a
single engine assuming a speed of no more than about 1.1 SQRT LWL.

We have Detroit 6-71 2-cycle diesels which are not efficient at low
speeds. Running single engine gets operating RPMs up to a normal
level. This is useful on long passages in relatively light winds and
calm seas. If the wind kicks up we need more power to maintain speed
and stability.

Tough finding a solution to that.
Just a few thing things that popped into my head, probably none
practical.
Re-propping to get revs up on both engines - non-starter because
you're running 2 engines, and waste heat kills fuel savings.
Transmission that can run both props on one engine input.
Makes sense for cruising speed, but probably too expensive/complex.
Feathering props. Probably more drawbacks than gain.
Easily detached props. Read to dive far asea, hoist, and get caught
with only one prop when it squalls? Didn't think so.
My favorite lame-brain idea is streamlined remote operated prop cowls.
Close when prop not in use, open otherwise.
Insane.

Do you have trans lube/heat problems when freewheeling a prop?
If you lock it down, will you still get 25% fuel savings?
Lots of drag there.

--Vic

On Wed, 24 Nov 2010 09:48:30 -0600, Vic Smith
wrote:

We have Detroit 6-71 2-cycle diesels which are not efficient at low
speeds. Running single engine gets operating RPMs up to a normal
level. This is useful on long passages in relatively light winds and
calm seas. If the wind kicks up we need more power to maintain speed
and stability.

Tough finding a solution to that.
Just a few thing things that popped into my head, probably none
practical.
Re-propping to get revs up on both engines - non-starter because
you're running 2 engines, and waste heat kills fuel savings.
Transmission that can run both props on one engine input.
Makes sense for cruising speed, but probably too expensive/complex.

Running two engines is always less efficient than one engine,
everything else being equal. An engine in motion has lots of
frictional and parasitic losses - things like pumps, alternators and
valve trains for example. DD 6-71s have an additional parasitic loss
from spinning the blower.

Feathering props. Probably more drawbacks than gain.

Feathering props are good although complex, expensive and difficult to
repair in the boondocks.

Easily detached props. Read to dive far asea, hoist, and get caught
with only one prop when it squalls? Didn't think so.

Not on my boat although I understand that a guy with a GB49 went from
Hawaii to San Francisco that way.

My favorite lame-brain idea is streamlined remote operated prop cowls.
Close when prop not in use, open otherwise.
Insane.

Good out of the box thinking, just a few details... :-)

Do you have trans lube/heat problems when freewheeling a prop?
If you lock it down, will you still get 25% fuel savings?
Lots of drag there.

At slow trawler speeds it is not that big an issue. We start the
other engine once in a while to recirculate the transmission lube. I
also check the temp with a heat gun from time to time when I'm doing
my engine room checks.

In theory locking it down is more efficient than letting it spin.
Locking it down is potentially dangerous however unless a built in
shaft braking system is used.

Check out

http://www.cruisersforum.com/forums/...est-37969.html

It's a lot of posts on the Cape Town to Brittany test. The boat had
1,600 Watts of solar panels, a wind gen and a 22KW diesel generator.

The African Cats poster also stated, "Regeneration with the
motors/generators will be done as minimal as possible in order to keep
the best average speed."

There's about 9 pages of posts and it seems the solar was king, with
diesel coming in second.

Rick