Calibrating the autopilot

[ferssini]

Hi Chuck!

I have a 32 footer sailboat with a wheel rudder.

I have a complete Evolution Autopilot system with ACU100 (wheel) and p70 control head, but without rudder reference trasducer.

I have done the autopilot calibration procedure correctly and the compass shows a 3° Deviation.

The vessel type is set to "Sail".

Nevertheless, when I am sailing on light winds at 4 to 5 knots of boat speed, with some side tide (1,5 knots), even setting the autopilot in "Performance" mode, it drives the boat in a "swinging" pattern of -let's say- 15° from port to starboard and back, as it have problems to steer the boat straight. This happens in all types of autosteering modes (Auto, Wind, GOTO a WP, Follow Route).

I also point that the sails are correctly set and there are very small waves (0,30 m).

Do you have any suggestions on how can I correct this "swinging" problem?

I suspect that at a low boat speeds with some side tide, the autopilot struggles to manage the combination of both factors (boat speed and tide).

Many thanks in advance for your help.

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum ferssini,

The Evolution autopilots are quite dependent upon having quality speed through water and GPS data available to them. This is particularly important for slow moving vessels operating under the influence strong current or wind. Is the vessel equipped with a speed through water sensor? Has it been calibrated and is it operating properly? If not, then it is recommended that the autopilot be configured to utilize GPS SOG rather than Speed (though water). Also, slow moving vessels operating under such influences may benefit from supplying the autopilot with rudder angle data. Accordingly, it is recommended that the autopilot be fitted with a rudder reference transducer should one not already have been installed as part of the autopilot's installation.

[ferssini]

Hi Chuck,

Thank you for your answer.
I do have a "speed through water sensor" (Raymarine D800) which is properly installed (connected through an ITC5 to the STNg network) and working fine. The ITC5 has the latest sofware update available, and the same for all the other instruments (i70, p70, ES7, EV100).
I also have another speed/depth sensor installed directly to an old Raymarine bidata 60 but not to the autopilot nor to the STng, which gives only a 0.3 knots difference with the D800, so I assume that the speed data received by the autopilot from the D800 via the STng net is correct.
Which is the part number for a wheel drive EV100 autopilot rudder sensor?
Best Regards

[Chuck - Raymarine - Moderator]

ferssini,

Raymarine does not offer a D800 transducer. Is it possible that you have a DST800 transducer and that it's speed transducer leads have been interfaced to the iTC-5? If so and this transducer has been calibrated and operational, then it would indeed be a suitable speed input for the system. With respect to rudder reference transducers, the Raymarine M81105 Rudder Reference Transducer may be used with any Evolution autopilot.

[ferssini]

Hi Chuck,

It is correct, it is a DST800 interfaced to the ITC5.

While searching the "Pilot configuration" on my ES7 plotter, I noticed that there is a value "Rudder Dumping" (which in my case is was automatically set in 3). I read the manual and found that this should not be changed by the user even though it is possible to modify it. There is no explanation in the manual for this "dumping" setting. Should it have any effect on the autopilot response to correct my problem?
Is there any other setting that I could modify in order to enhance the pilot´s response? For example, to manually set a "quicker" or "slower" "hard over time"?

My problem is that I have a small suitable space available to install that kind of rudder reference unit. That was the reason why I choose an external wheel autopilot rather than an internal one.

Best regards
Fernando

[Chuck - Raymarine - Moderator]

Fernando,

Please click here to view a Forum thread in which I had addressed this subject, including how to perform rudder damping. As indicated within the referenced thread, rudder damping is used to limit the degree of S-ing. The Evolution autopilots are designed to learn the vessel's handling characteristics and will automatically determine a value for rudder damping, and as such, adjustment of this setting need not typically be performed by the user as well. If the rudder overshoots and has to drive back or starts to hunt back and forth, then rudder damping level may be increased to reduce this behavior

The Hard Over time is used to indicate the handling characteristics of the vessel's rudder and should only be adjusted to specify the hard over to hard over time.

Irrespective of the difficulty with installation some installations may require a rudder referenced to address handling characteristics of the vessel.

[ferssini]

Hi Chuck,

I have tried the suggested solutions for the problem with the autopilot that I have posted.

I have decreased the rudder dumping value from 6 to 3 and also increased the time of the hard over from 9 to 12", and the "swinging" of the rudder seemed to be corrected. I still have to test it in some weather/tide conditions, but I am happy to tell you that the autopilot's boat handling is significantly better.

Many thanks for your help!
Best regards,

[Chuck - Raymarine - Moderator]

You're welcome.