Hunter 33.5 - Autohelm ST4000+

Fred

.
Sep 27, 2008
472
Hunter 33.5 Little Current, Ontario, CA
I’m trying to get the Wheel pilot on this new to me boat working properly. It does not appear to track well under sail, particularly when heeled. I set the Response Level to “2” and the Rudder gain to “1” which seems to give the best performance. It will hold until it gets a significant perturbation (eg gust or wind) and then it starts to swing wildly. I noticed that the flux gate is mounted off-center by about 3-4 ft. Not sure how much that would contribute to the poor performance. Do flux gates go bad after a while? (I’m not even sure if they have internal mechanical components) Any ideas?
 
Feb 27, 2004
167
Hunter 335 North East, MD
My fluxgate is off center and I haven't noticed any problems. When you state the boat is not tracking well when sailing are you setting it up to follow a compass course or angle to the wind ?
 
Oct 22, 2014
16,130
CAL 35 Cruiser moored EVERETT WA
Fred, over the years that fluxgate compasses have been in use, sailors have come to recognize that the machine can be temperamental. They can and have drifted. Creating chaos in the unsuspecting crew. I never trust a system. I check it then verify.

You said that "a significant perturbation (eg gust or wind)" causes the system to become unstable. Not a surprise. Read any of the AP manuals and you will be instructed to trim your boat to near neutral when using the AP. The AP is not a magician (though many believe that he AP has magical powers). The AP maintains a course while the boat is in balance relieving the helms person from the tedious chore of steering the boat. If the helm gets a knock (i.e. your Perturbation) the systems are ajar. The boat is no longer in balance, and it requires the help of the crew to reestablish this balance. Once trim has been reinstalled the AP should again be able to take over the tasks it is capable of doing.

I think the term "Auto Pilot" is a misnomer. I prefer to call it an "Assistant Pilot" on my boat. The Chief Pilot is me. I need to step in when things are ajar and reestablish the trim and the rules if necessary.

The newer EV100 Sensor appears to be an improvement on the fluxgate compass design.
 
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Feb 14, 2014
5,713
Hunter 430 Waveland, MS
Flux gates need calibration too.

Their position was set to avoid interference from large metal objects, like your engine.

Unfortunately the crew tends to store other metal objects nearby.:facepalm:

You can program your AP to change Sea States by a simple push of buttons at the Helm.

As you boat heals and/or rides waves, your rudder surface control changes. Thus your settings change.

Get the manual if you do not have one.
Jim...
 

Fred

.
Sep 27, 2008
472
Hunter 33.5 Little Current, Ontario, CA
Thanks for the input JS! I’ve been involved in quite a bit of electronic control/servo systems in my career. I certainly appreciate the limitations of the “assistant”. What bothers me most is that the system seems to respond in an underdamped manner. There seems to be an adjustment for the long term trim error (ie “integral” component) however it seems to need more damping (ie “derivative” component). It is not clear to me if that can be adjusted. Do you know if the EV100 sensor would work with the rest of the “older” system or do I need to upgrade the whole system?

My thought is to network the autohelm into my chart plotter/wind system ( the PO didn’t complete that conn) and determine if the system works better when tracking the apparent wind or chart plotter course rather than the magnetic compass.
 
Nov 6, 2006
9,226
Hunter 34 Mandeville Louisiana
If you don't have a rudder position indicator hooked to the ST 4000+, it will be difficult to "tune" .. My ST did that same thing until I installed a RPI sensor.. also, make sure there is no steel, iron, or other magnetic stuff near the fuxgate sensor. stuff like food tins, tools, chain, anchors, etc..The black thing above the steering quadrant is an RPI mounted upside down (so I could get it to fit/work)
EDIT: check the setting for "lock to lock" in the calibration.. it should be set as low as possible.. My lock-to-lock was less that the lowest setting and the pilot would suddenly jump to undamped oscillations when sailing.. The RPI overrides that setting and the pilot can then tell how far the rudder is turning when it gives a command..
P7160346.JPG
 
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Fred

.
Sep 27, 2008
472
Hunter 33.5 Little Current, Ontario, CA
Thanks Jim! So far the only real adjustments that I’ve managed to play with are the “response” and “rudder gain”. I’ll review the manual again to determine if I can change “sea state”.
 
Oct 22, 2014
16,130
CAL 35 Cruiser moored EVERETT WA
I had nothing on my boat when I purchased her. I bought the EV100 package. I believe the Sensor and the ACU are available as separate items. The ACU receives the signals and drives the motor to make the adjustments.

As Kloudie shares, I believe the rudder sensor will help in managing the damping you seek. It provides a data point to more quickly alter the course when the rudder gets pushed out of alignment from the set course by a sudden event (i.e. gust or wave). This items is a separate purchase. It is essential when using the hydraulic or linear drives on heavier boats than your Hunter.

The use of an AP is really an item for a cruiser. While the possibility exists to build a system with a tight tolerance, say 2 meters either side of a designated track, the question arises do you need that tolerance, and is it feasible at the cost boaters are willing to spend? I think Raymarine has brought to market an item that is compromised in both materials (mostly plastic) and course maintaining tolerance (within 2-3 degrees over 50 kilometers.) Maybe with boat trimming or attention to currents and wind changes you can maintain a tighter course. Are these marketing compromises acceptable? That is the question.
 
Feb 14, 2014
5,713
Hunter 430 Waveland, MS
however it seems to need more damping (ie “derivative” component)
You do know your controller functions.:cool::biggrin: [PID type]

There is little to none controller "derivative". Such would cause wild Rudder swings. [power boat type settings]
_____
integral” component [Response Level to “2”]
This is the adjustment part of the "off course" correction.

Gain = Sea State. [ Rudder gain to “1”] that says AP is very responsive.

The Gain function is what is normally changed at the helm, after you do a smooth seas calibration.

Note: the farther off course, the faster the Integral function tends to over correct.

The default setting are for a Sailboat.
Jim...
 
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Feb 14, 2014
5,713
Hunter 430 Waveland, MS
My lock-to-lock was less that the lowest setting and the pilot would suddenly jump to undamped oscillations when sailing
That is the "derivative" function. PID = GID types [Proportional Integral Derivative] or Gain = Proportional
Jim...

PS: Rudder Positioner needed for AP feedback. No feedback, not a controller.
 

Fred

.
Sep 27, 2008
472
Hunter 33.5 Little Current, Ontario, CA
PS: Rudder Positioner needed for AP feedback. No feedback, not a controller.
not to quibble but the system does use (magnetic)heading as a feedback loop so technically still a servo/controller system. I agree that a rudder position loop could help. Would love to see examples of how an RPI would be installed on the H33.5.
 

Fred

.
Sep 27, 2008
472
Hunter 33.5 Little Current, Ontario, CA
From what I can tell “lock-to-lock” is just the allowable rudder travel in degrees to prevent the AP from driving against the stops. Gain would be set by the “rudder gain” parameter.

Edit: or maybe it is the degrees that the wheel can turn if there is no RPI. I’ll have to check that.
 
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