Thanks David,
my information on the "feel at the wheel" came from a Raymarine rep. and
Simrad documentation. I have no first hand knowledge, but suspect it is a
fairly minor difference. The mechanical drive may use just as much juice,
but I have convinced myself that it less. I was less concerned about the
durability thinking that if I were doing heavy duty use of an autopilot,
that it would be with a Monitor windvane and not the electrical anyway. I
have also heard that the Raymarine "may" have better wind algorithms and I
am experienced with their wheel pilot and very comfortable with the user
interface. I ordered the Raymarine today.

"David&Joan" wrote in message
newsRkJd.438$Jt.39@fed1read02...
John:

I have used both a Raymarine ST6000 with a rotary electric drive and a
Simrad/Robertson AP11 with a hydraulic drive. There was no significant
difference in power consumption. The hydraulic drive (with an integral
pump)
only runs the pump when it needs to. If I watch the ammeter, I see about
1-2
amps normally and it jumps up to 3-5 amps when the pump kicks in. The
linear
electric drive does about the same.

In general, hyraulic pumps and cylinders are pretty robust and probably
are
less prone to failure. As others have said, with the hydraulic system
disengaged, there is very little drag on your steering. Mounting a self
contained hydraulic actuator is no different than a linear electric
actuator.

The Raymarine has a better user interface and I think, a better algorithm
for dealing with various sea states and imbalanced helm conditions.

So my vote would be Raymarine electronics with a hydraulic actuator.

David

Johnhh wrote:

Thanks David,
my information on the "feel at the wheel" came from a Raymarine rep. and
Simrad documentation. I have no first hand knowledge, but suspect it is a
fairly minor difference. snip

The comment about hydraulic systems having less feel may have been in
reference to a hydraulic primary or hand steering system as compared to
a mechanical hand steering system.

In a hydraulic steering system the helm is mounted on the shaft of a
pump or directly coupled to a pump with a loop of chain. That is a
closed loop system with a cylinder that pushes or pulls (depending on
which way the helm/pump is turned) on an arm on the top of the rudder
post.

The "feel" of helm movements is lost in the high mechanical advantage of
a hydraulic system. It can be rendered further imprecise by factors
such as the presence of any pockets of air trapped in the system and any
weep against pressure that occurs in the pump or cylinder.

Properly installed and maintained, a hydraulic hand steering provides
very little or no feedback at the hand to turning forces. It feels like
power steering did on older (1960's or so) American cars, no change in
turning forces from lock to lock. Newer cars have variable ratio power
steering that gives an impression of feedback with turning forces that
increase as you get further away from the neutral position.

If you have ever steered a boat with hydraulic steering that is badly
worn or has pockets of air in the steering loop, you'll never forget it.

Your autopilot, hydraulic or electric, is trying to maintain a heading
and will normally push and pull the same arm on the rudder post that
your manual steering does.

If a linear drive has any clutch slippage or hydraulic weepage the
course computer will make frequent to nearly continuous steering inputs.
The rudder wants to fall back to center and the AP keeps working to
steer to the set heading. If that happens you'll see it on an ammeter
as David describes.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

"Jack Erbes" wrote in message
...
The "feel" of helm movements is lost in the high mechanical advantage of
a hydraulic system. It can be rendered further imprecise by factors
such as the presence of any pockets of air trapped in the system and any
weep against pressure that occurs in the pump or cylinder.

Properly installed and maintained, a hydraulic hand steering provides
very little or no feedback at the hand to turning forces. It feels like
power steering did on older (1960's or so) American cars, no change in
turning forces from lock to lock. Newer cars have variable ratio power
steering that gives an impression of feedback with turning forces that
increase as you get further away from the neutral position.

Mmmm...., I have a hydraulic system and I can feel the propeller blades pass
the rudder when turning and when I am in very shallow water, the steering is
much heavier. No feedback eh?

Meindert

I have sailed on a 35ft motor sailor with manual hydraulic steering and
there was a lever on the wheel pedestal that you could shift to (somehow)
get feedback to the wheel. Otherwise, as described by others, there is
little or no feedback..

The skipper advised that we leave the feedback "off" for some reason and I
never tried it. One thing I did notice was, there was no reference to "wheel
center" in relation to center rudder. Without doing too much exploring, I
assumed that there was some slippage in the system (since it had done a
circumnavigation and more during it's 20+ years).

However, I believe that a manual hydraulic system should have feedback if
properly set up and maintained. I also believe that these systems offer a
good alternative to cable systems when the wheel must be at some far/remote
location.. I would assume that there are hydraulic AP systems that can be
integrated into an, otherwise, manual hydraulic system .

My opinion and experience, FWIW.

Steve
s/v Good Intentions
"Jack Erbes" wrote in message
...
Johnhh wrote:

Thanks David,
my information on the "feel at the wheel" came from a Raymarine rep. and
Simrad documentation. I have no first hand knowledge, but suspect it is
a fairly minor difference. snip

The comment about hydraulic systems having less feel may have been in
reference to a hydraulic primary or hand steering system as compared to a
mechanical hand steering system.

In a hydraulic steering system the helm is mounted on the shaft of a pump
or directly coupled to a pump with a loop of chain. That is a closed loop
system with a cylinder that pushes or pulls (depending on which way the
helm/pump is turned) on an arm on the top of the rudder post.

The "feel" of helm movements is lost in the high mechanical advantage of a
hydraulic system. It can be rendered further imprecise by factors such as
the presence of any pockets of air trapped in the system and any weep
against pressure that occurs in the pump or cylinder.

Properly installed and maintained, a hydraulic hand steering provides very
little or no feedback at the hand to turning forces. It feels like power
steering did on older (1960's or so) American cars, no change in turning
forces from lock to lock. Newer cars have variable ratio power steering
that gives an impression of feedback with turning forces that increase as
you get further away from the neutral position.

If you have ever steered a boat with hydraulic steering that is badly worn
or has pockets of air in the steering loop, you'll never forget it.

Your autopilot, hydraulic or electric, is trying to maintain a heading and
will normally push and pull the same arm on the rudder post that your
manual steering does.

If a linear drive has any clutch slippage or hydraulic weepage the course
computer will make frequent to nearly continuous steering inputs. The
rudder wants to fall back to center and the AP keeps working to steer to
the set heading. If that happens you'll see it on an ammeter as David
describes.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

On Tue, 25 Jan 2005 09:41:24 -0800, "Steve" wrote:

I would assume that there are hydraulic AP systems that can be
integrated into an, otherwise, manual hydraulic system .

==============================================

Yes, commonly available. One advantage to adding an autopilot to a
manual system is that you usually gain a rudder angle indicator in the
process.