On 2007-11-20 15:49:16 -0500, Wayne.B said:

On Tue, 20 Nov 2007 12:22:40 -0500, Martin Baxter
wrote:

Forgive my ignorance, I'm just not familiar with something this big. I
would think that you could just leave the tranny in gear and stop the
motor, or is there sufficient torque generated to turn the motor over?

The tranny is hydraulically actuated internally with its own pump
driven by the engine. With the engine off there is no pressure to keep
the clutches engaged. As long as the transmission is in gear however,
it is impossible to shut the engine down because of the prop rotation
being passed through. It's quite possible that there would be enough
torque to restart the engine if it did not disengage but there is no
way to find out.

I've always wondered... Why not put a feathering prop on at least one
of the shafts? Yeah, I know they're expen$ive (we have a MaxProp), but
it seems like it might be overall cheaper in the long run.

Then again, I'm not sure I've seen a 30" feathering prop. Nevermind....
MaxProp show up to 44" and some indication of a 4 blade; Autoprop shows
up to 36". Dang, I'd hate to pay their cost, but I don't much like
buying fuel or transmissions either.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

HK wrote:



We've got some guests coming north from Florida this week for the
holiday. Two hours in the plane and they're here.

Like magic! Wow!

-dk

On Wed, 21 Nov 2007 00:46:44 GMT, Jere Lull wrote:

I've always wondered... Why not put a feathering prop on at least one
of the shafts? Yeah, I know they're expen$ive (we have a MaxProp), but
it seems like it might be overall cheaper in the long run.

Then again, I'm not sure I've seen a 30" feathering prop. Nevermind....
MaxProp show up to 44" and some indication of a 4 blade; Autoprop shows
up to 36". Dang, I'd hate to pay their cost, but I don't much like
buying fuel or transmissions either.

It's a good thought and one that I might consider if I have to reprop
again sometime in the future. Do you have any idea how they work? Is
the pitch adjustable in some way or do they just self-feather from the
force of the water like a folding prop?

The other important issue is reliability. If you are docking a 60,000
lb boat in close quarters you *really* want to know that forward and
reverse are working exactly as planned. There is no fending off by
hand if something goes wrong. The reality of today's boat insurance
market is that if you have an expensive liability claim from damage to
another boat, you are probably going to get cancelled and have trouble
finding another policy. You pretty much have to self insure for all
but the very largest losses these days.

"Wayne.B" wrote in message
...
On Tue, 20 Nov 2007 04:02:00 GMT, "Glenn \(s/v Seawing\)"
wrote:

Fogive my ignorance. Your GB...works okay to shut down an engine and run
on
a single engine, rather than throttle back both? Does the drag of the
stationary prop still make it worth it?

Good question. If you throttle back both engines to run at or below 7
knots, they end up running barely above idle speed which is bad for
them over an extended time. By running a single engine you can keep
it at an RPM range where it is developing a half way decent amount of
power. I still rev it up once in a while for 10 minutes or so.

The other issue with single engine is wear and tear on the
freewheeling transmission. The trannys depend on the engine running
for cooling and lubrication. The manufacturer says that it is OK to
let them freewheel at slow speeds but recommends starting the engine
every two hours for a few minutes.

Economy improves mostly as a result of slower speed. Once you get
above 1 x SQRT(LWL) increased speed results in exponentially higher
hull drag as more energy goes into the wake.

This has got Dad and I talking about possibilities. He cruises on a GB42 &
I on my Gulfstar 41 Sloop. We've been trying to slow his boat down enough
so I can keep up on a regular basis. I was thinking of buying a small fleet
of large dingies to tow behind him to slow him down, but that's an expensive
option. Sounds like your idea may be well worth experimenting with. The
primary concern for me, would be damage to the transmission....those puppies
are expensive. Maybe this'll help Dad cut down on his fuel bill. I
constantly tease him 'bout it...he normally burns 4.5gph while I about
2/3gph....when I'm motoring. I sure like his GB though...maybe when I get
tired of sailing (whenever that could be). :-)

Glenn.
s/v Seawing.

"Dan" wrote in message
...
HK wrote:



We've got some guests coming north from Florida this week for the
holiday. Two hours in the plane and they're here.

Like magic! Wow!

-dk

And 3 hours in airports!

HK wrote:

We've got some guests coming north from Florida this week for the
holiday. Two hours in the plane and they're here.

Like magic! Wow!

And I've got some swamp land in Arizona we need to talk about.

Lew

On 2007-11-20 22:35:18 -0500, Wayne.B said:

On Wed, 21 Nov 2007 00:46:44 GMT, Jere Lull wrote:

I've always wondered... Why not put a feathering prop on at least one
of the shafts?

It's a good thought and one that I might consider if I have to reprop
again sometime in the future. Do you have any idea how they work? Is
the pitch adjustable in some way or do they just self-feather from the
force of the water like a folding prop?

They self-feather from the force of the water. The blades reverse to a
different pitch in reverse, thus vastly improving the "brakes". The
blades are geared, so it's nothing like a folding prop. If you punch
reverse, you'll have it in spades.

We have the "cheaper" AutoProp that requires taking the hub apart to
re-pitch, but they have one that can be re-pitched in the water by
adjusting the hub.

The Autoprop is self-pitching to the load, so will have a more linear
power/rpm curve, and a bit more load at lower RPMs.

The other important issue is reliability. If you are docking a 60,000
lb boat in close quarters you *really* want to know that forward and
reverse are working exactly as planned. There is no fending off by
hand if something goes wrong. The reality of today's boat insurance
market is that if you have an expensive liability claim from damage to
another boat, you are probably going to get cancelled and have trouble
finding another policy. You pretty much have to self insure for all
but the very largest losses these days.

I believe you'll find that you'll need a less throttle to maneuver and
a closer correlation between forward and reverse settings.

I suppose it's possible to break one, but they're built pretty heftily
and seem to survive charterers' errors. In fact, I don't believe I've
heard of one breaking, though I suppose they get dinged as often as
fixed wheels.

I'd check with the manufacturers, of course, for suitability, but if
they're building them 3'+ in diameter, they're putting them in some
pretty big boats.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

Wayne.B wrote:
On Tue, 20 Nov 2007 12:22:40 -0500, Martin Baxter
wrote:

Forgive my ignorance, I'm just not familiar with something this big. I
would think that you could just leave the tranny in gear and stop the
motor, or is there sufficient torque generated to turn the motor over?

The tranny is hydraulically actuated internally with its own pump
driven by the engine. With the engine off there is no pressure to
keep the clutches engaged.


Ah I see now, makes for a bit of a sticky wicket.

Cheers
Marty

On Wed, 21 Nov 2007 05:21:29 GMT, "Glenn \(s/v Seawing\)"
wrote:

This has got Dad and I talking about possibilities. He cruises on a GB42 &
I on my Gulfstar 41 Sloop. We've been trying to slow his boat down enough
so I can keep up on a regular basis. I was thinking of buying a small fleet
of large dingies to tow behind him to slow him down, but that's an expensive
option. Sounds like your idea may be well worth experimenting with. The


primary concern for me, would be damage to the transmission....those puppies
are expensive.

Tell me about it. Four man days to get one out, two to rebuild it,
three to put it back in, and about two Boat Units worth of parts.

Maybe this'll help Dad cut down on his fuel bill. I
constantly tease him 'bout it...he normally burns 4.5gph while I about
2/3gph....when I'm motoring. I sure like his GB though...maybe when I get
tired of sailing (whenever that could be). :-)

What if he towed your Gulfstar? That would slow him down! :-)

On Wed, 21 Nov 2007 15:35:14 -0500, Wayne.B
wrote:

On Wed, 21 Nov 2007 05:21:29 GMT, "Glenn \(s/v Seawing\)"
wrote:

This has got Dad and I talking about possibilities. He cruises on a GB42 &
I on my Gulfstar 41 Sloop. We've been trying to slow his boat down enough
so I can keep up on a regular basis. I was thinking of buying a small fleet
of large dingies to tow behind him to slow him down, but that's an expensive
option. Sounds like your idea may be well worth experimenting with. The


primary concern for me, would be damage to the transmission....those puppies
are expensive.

Tell me about it. Four man days to get one out, two to rebuild it,
three to put it back in, and about two Boat Units worth of parts.

Maybe this'll help Dad cut down on his fuel bill. I
constantly tease him 'bout it...he normally burns 4.5gph while I about
2/3gph....when I'm motoring. I sure like his GB though...maybe when I get
tired of sailing (whenever that could be). :-)

What if he towed your Gulfstar? That would slow him down! :-)


Basically diesel fuel consumption is a factor of horsepower produced.
There are formula all over the Net.

The Grand Banks hulls are semi-displacement hulls and probably produce
an optimum distance/fuel consumption at higher speeds so just puling
the throttles back will probably not accomplish a really major
increase in fuel economy.

If you really want to get the best fuel/hour figure do what the
trawler yachts do and stick in a couple of 50 HP engines, run them at
about 35 HP which will be at a high enough power setting to keep the
engines from carboning up and be pretty economical.

Or you can get what I have in my 40 ft. boat - a 40 HP engine. Of
course I've got sails too.....=:-)


Bruce-in-Bangkok
(Note:remove underscores
from address for reply)