Can anybody explain what rate stabilizers, how they do it and whether
they are worth the money for slow moving displacement boats?

Many thanks,

Steve

Steven Dubnoff wrote in message
...

Can anybody explain what rate stabilizers, how they do it and
whether
they are worth the money for slow moving displacement boats?

Earlier autpilots sensed 'heading error' through a fluxgate
compass, and applied rudder proportional to heading error to
bring the vessel back onto course. To allow for change of trim
calling for a new neutral rudder angle, they also integrated any
persistent heading error and applied rudder to cancel that out.

A rate stabiliser measures the rate at which heading is changing
from a rate of yaw sensor and applies rudder to cancel that rate
of yaw. This makes for a more active rudder (bigger power
consumption) but theoretically a steadier course.

I haven't tried it on boats (only on airplanes, where it works a
treat) so can't comment on value, tho' theoretically I'd expect
better downwind steering.

JimB, Yacht RAPAZ, sadly for sale to buy that Greek house . . .
http://homepage.ntlworld.com/jim.bae...cification.htm

"Steven Dubnoff" wrote in message
...

Can anybody explain what rate stabilizers, how they do it and whether
they are worth the money for slow moving displacement boats?

Many thanks,

Steve

Put one on my 50 foot equipped with a Raytheon (pre Raymarine 6500) and it
made a world of difference, especially in a following sea. Before the
installation in any following sea conditions greater then a foot or two of
chop I had to steer manually as the boat was all over the place on
autopilot. Put in the gyro rate sensor and the Autopilot works great in 6
footers although that is not my choice of conditions to be cruising in. I
recommend the rate sensor option strongly to anyone who asks. For the
record I have no connections to Raymarine and in fact prefer Foruno to them.
Fred

We installed Raymarine's Smart Heading Sensor in Lionheart, an Amel
Sharki 41 ketch. As the B&G Pilot electro-hydraulic autopilot uses
its own fluxgate, not the data on the NMEA bus, for compass heading, I
don't see any difference. I don't think it would make any difference,
anyways, as the B&G Pilot is just like having a ghost at the helm it's
so smooth and powerful. It constantly "learns" from every turn how
the boat handles and corrects any overshoot, etc. The ram is so quick
and powerful back there on the rudder post, compared to the old
Autohelm 4000 jerking away so slowly on the wheel, it can hard over
the helm to compensate really fast......if you don't get your knee
knocked as the wheel spins around hard.

Look at the Raymarine Smart Heading Sensor manual on:
http://www.raymarine.com/raymarine/S...81198_1www.pdf

Go to page 9 of the Gyro installation and read where it says it has to
be within 10 degrees of vertical to work right.

Name 3 sailboats you know of that remain within 10 degrees of vertical
so it will work right. I can't find any here, either, especially
ours. I'm not sure what 30 degrees of heel does for it. Does it
render it useless?



On Sun, 29 Feb 2004 19:46:38 -0800, Steven Dubnoff
wrote:


Can anybody explain what rate stabilizers, how they do it and whether
they are worth the money for slow moving displacement boats?

Many thanks,

Steve





Larry W4CSC

No, no, Scotty! I said, "Beam me a wrench.", not a WENCH!
Kirk Out.....

Actually Raymarine wants it within 10 degrees vertically and have in the
past, said mount it athwartships. Recently they said it can be side mounted.
It is really not a gyro but an accelerometer device. On a sailboat I would
still suggest mounting it to a bulkhead that is vertical with respect to the
pitch axis.
Doug, K7ABX


"Larry W4CSC" wrote in message
...
We installed Raymarine's Smart Heading Sensor in Lionheart, an Amel
Sharki 41 ketch. As the B&G Pilot electro-hydraulic autopilot uses
its own fluxgate, not the data on the NMEA bus, for compass heading, I
don't see any difference. I don't think it would make any difference,
anyways, as the B&G Pilot is just like having a ghost at the helm it's
so smooth and powerful. It constantly "learns" from every turn how
the boat handles and corrects any overshoot, etc. The ram is so quick
and powerful back there on the rudder post, compared to the old
Autohelm 4000 jerking away so slowly on the wheel, it can hard over
the helm to compensate really fast......if you don't get your knee
knocked as the wheel spins around hard.

Look at the Raymarine Smart Heading Sensor manual on:

http://www.raymarine.com/raymarine/S...81198_1www.pdf

Go to page 9 of the Gyro installation and read where it says it has to
be within 10 degrees of vertical to work right.

Name 3 sailboats you know of that remain within 10 degrees of vertical
so it will work right. I can't find any here, either, especially
ours. I'm not sure what 30 degrees of heel does for it. Does it
render it useless?



On Sun, 29 Feb 2004 19:46:38 -0800, Steven Dubnoff
wrote:


Can anybody explain what rate stabilizers, how they do it and whether
they are worth the money for slow moving displacement boats?

Many thanks,

Steve





Larry W4CSC

No, no, Scotty! I said, "Beam me a wrench.", not a WENCH!
Kirk Out.....

Go to page 9 of the Gyro installation and read where it says it
has to
be within 10 degrees of vertical to work right.

Name 3 sailboats you know of that remain within 10 degrees of
vertical
so it will work right. I can't find any here, either,
especially
ours. I'm not sure what 30 degrees of heel does for it. Does
it
render it useless?

No. Close hauled (when sailing vessels heel most) the autopilot
doesn't have to work hard, and performance isn't an issue. Yaw
rates are small, and the pitch inputs (producing spurious yaw
inputs) are small.

Downwind is the problem area. Heel angle is random. Measurements
of yaw rate will be disturbed from time to time when there's a
temporary roll angle on, which may make the autopilot overactive.
But the inputs as you roll from side to side will cancel out.
Just like the typical helmsman's effort when sailing downwind in
a death roll!

The ideal system has an earth stabilised sensor! Who makes those?
What price?

JimB (going off line for two weeks; to sell the boat?)
Yacht RAPAZ, sadly for sale,
http://homepage.ntlworld.com/jim.bae...cification.htm

The ideal system has an earth stabilised sensor! Who makes those?
What price?


Not sure if this is really earth stabilized (like an INS) but KVH made
something a few years ago called a Digital Gyrocompass, had inclinometers, rate
gyro accelerometers and a flux gate. Cost several K. No longer made, but they
show up on eBay from time to time, usually for under $400. Has NMEA heading
outputs and also synthetic gyro stepper outputs. KVH's Gyrotrac was the
successor product but they are junk according to several commercial tuna
fishermen who smashed theirs and sent the pieces to KVH after KVH refused to
support them post warranty. They ALL failed within a year after warranty
expiration. Worked GREAT until failure, rock steady accurate heading no matter
what the ship was doing in the other axes, but not a long lasting product.