Windvane Comparison

Yacht self steering Windvanes considering 2 Types:

Servo Pendulum Windvane.

Vessel is steered by a servo rudder linked to the main rudder; therefore rudder volume is increased as both rudders work together.

The servo rudder is controlled by a light airfoil / vane (horizontal axis type). The force required for controlling the servo is approximately 1/3 of the force required by an auxiliary rudder.

Auxiliary Rudder Windvane.

Vessel is steered by the auxiliary rudder only. A large auxiliary rudder is required, as the main rudder is locked; reducing the control rudder area. The auxiliary rudder is controlled by a large airfoil /vane (horizontal axis type).

PLEASE NOTE: Yacht designers calculate the minimum rudder size to steer the vessel, so the assumption that a smaller auxiliary rudder will suffice is questionable.

The fundamental requirements of a windvane steering system.

When you compare windvane systems, there are three fundamental factors to consider:

  • Low friction, for sensitivity in lights winds
  • Light weight, for quick response in wind shifts
  • Low drag, to avoid impairing yacht’s windward performance

The following table details the main differences between the service pendulum windvane technology (as used by Neptune Windvane), and auxiliary rudder windvane (as used by some of our competitors).

CriteriaServo Pendulum WindvaneAuxiliary Rudder Windvane
Maximum Vessel Size38 tons / 54 ft. Length12 tons / 42 ft. length
For larger vessels, increasing the dimensions of the auxiliary rudder should be considered.
Main rudder does most of the steering so a substantial mount is not required. The correct servo to helm gearing and routing of the control lines requires careful design.
Requires heavy mounts and struts, as all the steering loading relies on the Auxiliary rudder.
Mounting Off CentreYesYes
Emergency Rudder UseFair
Lock the powerarm on cleats
Unsettled Sea Wind Strength Beaufort 5 IncreasingGood
Slacken airfoil clamp, Lower vane in slot &/or tilt back away from wind direction. Alternately fit heavy weather vane.
Recommended use autopilot or main helm.
Vessel with Weather HelmGoodPoor
Try reducing and/ or adjusting sail to remove weather helm
Reaching –Wind on the QuarterGoodTry reducing and/ or adjusting rig.
Light WindGoodGood, on flat sea
Sailing Close to the WindGood
Very little loss in windward performance due to small rudder and vane. The Neptune is capable of tacking itself when the airfoil is rotated 180 degrees. It simply drives the ship around onto the opposite tack. The vessel sheets require releasing and hauling in.
Large vane+ auxiliary rudder increases drag
Manoeuvrability using EngineGood
Use the main helm. Disconnect control lines. Rotate the servo rudder out the water.
Auxiliary rudder hinders use of main helm.
Removing RudderEasy
Rotate the servo rudder out of the water.
A lanyard is attached, the locking device unlocked then the rudder should slip downwards off the rudder shaft bottom end.
Installing RudderEasy
Rotate Servo Rudder back into the water.
When under way almost impossible