Rudder Control - CPT AUTOPILOT Wheel Pilot Operation Manual

Rudder Control

The Rudder control turns the autopilot on, and determines how far the boat's wheel (and rudder) turns when a
heading correction is needed; the response is the same for both port and starboard corrections and will not
work well with play in the steering system. Low settings result in smaller wheel corrections, higher settings in
larger wheel corrections. The corrections are proportional to the amount of heading change needed. The best
rudder setting will be high enough to return the vessel to heading with just one or two motor pulses or
corrections. If the pilot responds with many smaller repeated corrections in one direction, raise the rudder
setting.
The rudder control performs like a helmsman in a fog who can only see the compass. If this helmsman is told
to move the wheel exactly one inch for each five° heading error, he will do exactly that every time a correction
is needed. If these motions result in under-control and sluggish corrections, you can tell him to move the
wheel further for a given correction.
The boat must be balanced for consistent steering, it must respond to the rudder in a consistent manner; the
rudder dial sets the rudder response for one consistent response. It will not adjust for sloppy or excessive play
in a boat's steering system.
The rudder control is used to match the CPT's response to your boat's steering needs. Some boats take many
turns of the wheel to move the rudder, while others take only a few. The rudder control can adjust for this.
Every boat also responds somewhat differently to the rudder. Generally full keel boats with more turns lock-
to-lock take a higher rudder setting, but this rule does not always follow for some spade-rudder boats.
If the rudder control is set too high for your boat, the wheel will turn too far; the boat will over-steer too far
port and starboard. Lower the rudder setting.
The most common mistake seems to be setting the rudder setting too low. If the rudder control is set too low,
the autopilot will make many small repeated corrections in one direction to return to the desired heading, and
will spend a lot of time on one side of the rhumb line. The boat may gradually fall off and the pilot will not
keep the boat on heading. Almost all boats require a rudder setting of 4 or higher.
Either of these actions is relatively easy to identify and, with some experimentation underway, you should be
able to find the correct setting for your boat. A rudder setting that works while sailing in lighter winds may
have to be raised when winds increase.
A boat may require a slightly higher rudder setting at low speeds than at higher speeds. A sailboat may require
a higher setting when running than when beating and a higher setting when sailing than when motoring.
Full Keel Boats: A full keel boat with 3-4 turns lock-to-lock will typically use a rudder setting of 5-6.
Fin Keels and Spade Rudders: Response to the wheel may be more sensitive. The rudder setting will depend on
the boat's response to the rudder, and you will need to see what setting works best. It may take more balancing
and de-tuning for steady steering and keeping the boat from reacting to every gust or condition. With
increased speed downwind, response to the rudder increases, and lowering the rudder setting slightly works
well. If the boat is easily under-steered, over-steered, or has wheel play, the rudder setting may be a
compromise between the two.
If you are becalmed, stuck in irons or not making headway, disengage the CPT. The CPT will continue to try
and make heading corrections, but the vessel will not respond to rudder changes. If left unattended the rudder
could eventually hit the rudder stops.
(Avoid hitting the rudder stops; if it occurs a looser belt provides some give and you will hear a warning thump
as the belt jumps in its cogs; but if the belt is over-tensioned or used with a tensioner it eliminates any give in
the system and the shear pins are designed to shear if the belt doesn't jump)
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