Using it well · 6 minute read
Autopilot gain and counter rudder tuning
What rudder gain, counter rudder and response actually do, how adaptive pilots reduce the fiddling, and a sea-trial method for tuning your own boat.
Autopilot tuning has a reputation for black magic that it does not deserve. There are only a few settings on most systems, each one does something you can see from the cockpit, and a methodical hour on the water will get you a boat that steers better than any amount of menu diving at the dock.
Modern adaptive systems have shrunk the job. A Raymarine Evolution, a Garmin Reactor 40 or a B&G pilot with a current course computer will learn a good deal about the boat by itself, and many owners never change a setting. But adaptive is not magic, and there are conditions where a human still knows better than the algorithm.
Key facts
- Rudder gain
- How much helm the pilot applies per degree of error
- Counter rudder
- How firmly it takes the helm off to stop the swing
- Response
- How hard the pilot works to hold the course
- Method
- One change at a time, then watch for a full minute
- Sea state
- Following seas usually need a lower response, not more gain
- Record
- Write the settings down and date them
Rudder gain, counter rudder and response settings
Rudder gain is the proportional term. It sets how much rudder the pilot applies for each degree the boat is off course. Too little and the boat wanders lazily off the line. Too much and every small error produces a large correction, and the boat starts to weave.
, sometimes called rudder damping or derivative gain, decides how firmly the pilot takes the helm off as the boat swings back towards the course. Its job is to stop the swing at the right moment. Too little and the boat sails straight through the heading and has to come back. Too much and the boat approaches the course sluggishly and never quite gets there.
Response, performance level or sea-state setting is the master control on most modern systems. It trades steering accuracy against work done by the drive. High response holds a tight course and uses more power and more drive wear. Low response lets the boat move around a little and is far easier on the gear, which is usually what you want on a long downwind passage.
Adaptive autopilot tuning and manual settings
Current course computers use rate of turn from a nine-axis sensor to anticipate rather than react, and they adjust their own behaviour to the boat's speed and loading. Raymarine calls its implementation Evolution AI, Garmin and B&G have equivalents, and in practice these systems steer a well-set-up boat properly out of the box.
What they do not do is fix an underlying problem. Adaptive tuning cannot overcome a boat that is badly overpowered, a rudder reference that reads wrong, air in the hydraulics or a drive that is too slow. If the pilot steers poorly and the basics are good, look at those before diving into the menus.
They also do not know about your preferences. A racing crew wants a tight course and will accept drive wear and power. A cruising couple crossing the Coral Sea wants the drive to work as little as possible. That is a response level decision, and it is yours.
Fix the boat first, then the settings
Controlled sea trial method for autopilot tuning
Start in flat water in ten to fifteen knots with the sails properly trimmed. Engage the pilot on a close reach and watch the boat for two full minutes without touching anything. Note whether it holds within a couple of degrees, wanders slowly, or weaves rhythmically.
Make one change. If it wanders, raise rudder gain one step. If it weaves, lower it one step. Watch for another two minutes. Keep going until the boat sits on the course with small, frequent, gentle rudder movements. Then work the same way, judging it on how the boat settles after a deliberate twenty degree course change.
Now go and do it again in a seaway. Everything you learned in flat water changes when the boat is being pushed around, and the settings that felt crisp at the marina will feel frantic in a two metre swell off Sydney Heads. The second half of the trial is where the useful numbers come from.
- Trim the boat properly and note the helm angle before you start
- Change one setting, then observe for at least a minute or two
- Judge gain on course holding, counter rudder on how the boat settles after a turn
- Repeat upwind, on a reach and dead downwind
- Repeat in a seaway, not just in flat water
- Write down the final numbers, the date, the wind strength and the sea state
Autopilot tuning differences for sail and power boats
A sailing yacht's steering load changes constantly with heel, sail balance and wave action, and the pilot is working against a boat that wants to round up. Most sailing tuning is about coping with weather helm and with the yaw a following sea produces.
A planing power boat has a different problem: at speed a small rudder movement produces a large course change, so the pilot needs low gain and quick response, and it must not chase every wave. A displacement motor cruiser at nine knots is the easiest steering job of all and usually needs very little.
Heavy displacement cruising yachts sit at the other end. They respond slowly, so the pilot must apply helm early and take it off early, which usually means moderate gain with generous . Expect to use different settings under power and under sail, and check whether your system stores separate profiles.
Sailing autopilot response and recovery features
Raymarine's is a sailing-specific function in the Evolution software aimed at reducing the rudder movement caused by a boat's hydrodynamic balance changing with heel and speed. Owners generally report calmer steering downwind with it configured correctly. Check what your software version offers and how the manual says to set it.
B&G's sailing pilots include gust and recovery behaviours in their settings, intended to keep the boat under control when a gust hits and to bring it back to course without a violent correction. On H5000 systems the options are deeper again, and racing crews spend real time on them. Refer to the current documentation, because these options move between software releases.
Furuno's NavPilot family includes and , which are less about tuning and more about how the pilot and the helmsman share control. They are worth understanding for the same reason: they change what the boat does when you grab the wheel.
Record tuning changes after loading and seasonal changes
Boats change. A yacht loaded for a six week cruise with full tanks, a dinghy on the foredeck and stores aboard steers differently from the same boat empty on a club race. Winter sailing in Tasmania and summer sailing in the Whitsundays put the same pilot in very different sea states.
None of that means constant fiddling. It means having two or three known-good setups rather than one, and changing between them deliberately. Most systems make this easy through the response level alone.
Write the numbers on a card and keep it with the ship's papers. When a new crew member or a delivery skipper takes the boat, that card is the difference between a pilot that steers and an afternoon of guessing.
Questions
Frequently asked
What is the difference between rudder gain and counter rudder?
Rudder gain sets how much helm the pilot applies for a given course error, so it controls how hard the boat is pushed back towards the line. Counter rudder decides how firmly that helm is taken off as the boat swings back, so it controls whether the boat settles or sails straight through the course. Gain fixes wandering, counter rudder fixes overshoot.
Do I need to tune a modern adaptive autopilot?
Often not, because systems like Raymarine Evolution, Garmin Reactor 40 and current B&G pilots learn the boat and steer well with default settings. You will still want to change the response or sea-state level for different conditions, and heavy boats, planing hulls and following seas sometimes need a nudge. Always fix trim, rudder reference and drive problems before touching the gains.
My pilot steers badly in a following sea. What should I change?
Lower the response or performance level first rather than adding gain, because the boat is being yawed by waves rather than drifting off course. Check sail trim as well, since a boat pressed up under too much kite will round up whatever the pilot does. On some systems a sailing-specific function such as Hydro-Balance helps noticeably downwind.
Should I use different settings under power and under sail?
Usually yes. Under power the boat is upright, tracking steadily and easy to steer, so a lower response saves power and wear. Under sail the load changes with every gust and wave. Check whether your system stores separate profiles or whether you need to change the response level manually.
How long should I wait after changing a setting?
At least a minute or two of steady sailing before you judge anything. Autopilot behaviour changes with each wave set, and a decision made after ten seconds is usually a reaction to one wave. Change one setting at a time, observe properly, and write down what you did.
Practise autopilot operation with an instructor
Habits are learned at the helm with someone watching. The training section explains what a good instructor covers and where to find one in your state.