Windvanes 101Crash Course in Selfsteering Systems
Three Keys to Successful Vane Steering
Before we look into the various ways people have tried to solve the vane steering problem you should understand that the particular design of the vane gear is not the only thing which determines its performance. The characteristics of the boat and the skill of the operator are very important.
1. The Boat
As different as sail boats are in appearance, rigging, size, speed, performance, etc., it is obvious that the properties of the yacht will influence the performance of the vane gear. Any characteristic that contributes to balance and makes it easy to trim the boat to stay on course helps the performance of the vane gear. Any characteristic that makes it easy to steer the boat back on course after a deviation is positive. Thus moderate size (30'-55'), moderate displacement, moderate keel, reasonable rudder response and an easily balanced sail plan are some important contributing factors.
2. The Operator
Top windvane performance requires a balanced boat. Although true for autopilots also, vane gears are especially affected by gross errors in choice and trim of sails. An inexperienced skipper can smother the performance of the best vane gear.
Balancing the boat for self-steering involves setting things up so that the boat has a tendency to stay on the desired point of sail. If a wave or a change in the strength of wind takes the boat off course the balance trim should produce a tendency for the boat to return to course by itself. Through years of experience we have found that the common mistake by first time vane sailors is to over-canvas and over-sheet. The sailors that get the fastest and best results are those that have spent some time trying to balance their boat for self-steering without a vane gear prior to getting one.
Although a good vane gear can be quite forgiving the best performance will be achieved when the vane is only asked to make small corrections to keep a well balanced boat on track. Usually, the new vane sailor will find that a bit of experience leads to great improvements. The vane actually teaches you a lot about sailing and trimming your boat.
3. The Points of Sail
The particular point of sail is of importance to the performance of a vane gear. Most boats can be trimmed to self-steer by themselves when going hard to weather. Consequently, most vane gears will work well when beating. Running or reaching are trickier. When the boat is moving downwind its own speed forward causes a loss of apparent wind, which weakens the signals from the air vane sensor. In light winds they can become outright erratic as the air vane gets affected more by the boat's rolling, than by the wind.
A reach can be difficult if the wind varies a lot in strength. A hard puff can induce a lot of weather helm. A temporary lull can cause a lot of lee helm. In either case it may require quite a bit of rudder to keep the boat from rounding up or bearing off.
As stated, some boats are easier to balance to overcome these problems. The operator can do a lot to minimize them also. The myth that vane gears do not steer downwind is simply not true provided they are reasonably designed, engineered and operated.