ComNav 1500 / 1510 Autopilot - 24 -
3. ADVANCED OPERATION
3.1 Adjusting Response (See Calibration Menus).
Note: the rudder [RUD] and counter rudder [CRD] settings are inter-related and
may effect the performance of each other. Setting by trial and error may be
required.
3.2 Rudder [RUD] Function
The most critical adjustment for good steering is the rudder. Too high a setting will
cause excessive amounts of rudder to be given that force the vessel to hunt rapidly
back and forth across the course. Too low a setting lets the vessel slowly fall of
course with repeated corrections required to get back on course. The rudder should
be set to the position where positive control of course is achieved without undue
activity. Run the vessel at its cruising speed and make a course change with the
keypad of 40°. The vessel should not overshoot by more than 3° to 4°. Adjust the
rudder until this is achieved.
3.3 Sea State [SEA] Function
The parameter is a combination of yaw dead-band (compass sensitivity) and
compass damping. The minimum setting may only be used under calm sea
conditions to avoid unnecessary rudder correction due to compass acceleration
errors. Smaller vessels and high-speed vessels, which are subject to more
acceleration in lighter seas, will have to use higher settings. Larger and more stable
vessels can use lower settings since there is less compass disturbance. The
factory default setting should work on most vessels in light to moderate sea
conditions. Following seas, no matter how rough, require lower settings to catch
course error trends quickly in order to minimize excessive yaw.
3.4 Counter Rudder [CRD] Function
This feature senses the rate of change of heading and gives additional rudder
corrections if the vessel is rapidly falling off course, and backs off the rudder as a
vessel approaches the desired heading. Its effect is to rapidly catch the tendency to
yaw in a quartering sea, provide initially high rudder control when making a large
course change and to decelerate the swing of the bow as vessel approaches the
desired course. When using this feature, course holding of heavy and difficult to
steer vessels is greatly improved. Insufficient counter rudder will allow the vessel to
overshoot on large course changes and too much will cause unnecessary rudder
corrections and a tendency to stop short of coming to a new course, requiring
several successive corrections before easing up to the new heading. To optimize
counter rudder, initially set it to minimum and adjust the rudder so that the vessel
responds smartly to a 40°-course change with less than 3° to 4 ° of overshoot.
Then increment the counter rudder one step at a time while testing 40 °-course
changes, until the vessel achieves an overshoot of 2° or less. Remember any air
in the hydraulic system will prevent precision control.
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