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).
|Criteria||Servo Pendulum Windvane||Auxiliary Rudder Windvane|
|Maximum Vessel Size||38 tons / 54 ft. Length||12 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 Centre||Yes||Yes|
|Emergency Rudder Use||Fair|
Lock the powerarm on cleats
|Unsettled Sea Wind Strength Beaufort 5 Increasing||Good|
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 Helm||Good||Poor
Try reducing and/ or adjusting sail to remove weather helm
|Reaching –Wind on the Quarter||Good||Try reducing and/ or adjusting rig.|
|Light Wind||Good||Good, on flat sea|
|Sailing Close to the Wind||Good|
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 Engine||Good|
Use the main helm. Disconnect control lines. Rotate the servo rudder out the water.
Auxiliary rudder hinders use of main helm.
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.
Rotate Servo Rudder back into the water.
When under way almost impossible