Windvanes 101—Crash Course in Selfsteering Systems

Engineering

The different principles presented cover practically all vane gears available today. As we have seen, some of these principles are not feasible because they do not solve the problem of the weak force of the air vane or do not provide a sufficiently powerful steering device to control the boat. As faulty design principles can be the reason for non-performance, so can faulty engineering of a perfectly sound principle.

The trouble in actually putting a vane gear together is that it will be subject to constant work, heavy wear,substantial loads and all kinds of abuse from the salty sea. At the same time it is supposed to transmit fickle signals and turn them into vastly more power for steering corrections. If you build the gear with only ruggedness in mind the heaviness of linkages and moving parts will make it as useless as a cast iron airplane, which may last indefinitely but will never fly. If you build too flimsily there will be a crash on take off. The secret in putting together a good vane gear is to realize that the air vane must be able to activate the servo device, even if its signals are just feather light. This is achieved by using good bearings and relatively light linkage. As the forces involved in this part of the vane gear are slight, you do not have to use excessively heavy construction.

Once the servo device is activated the forces and loads are increased dramatically, but now you can provide a lot of a strength as it is no longer a question of babying a fickle signal but of transmitting a powerful steering response. This may sound simple enough, but you can be sure that there are many vane gears with unnecessarily deficient performance in light winds and downwind, due to over building and friction in the air vane to servo device connections. If this part of the vane system does not move freely at the slightest touch the vane gear will not perform well, unless it howls.

Apart from this general design consideration a number of engineering aspects should be looked at closely in appraising a vane gear:

Auxiliary Rudder vs. Servo-Pendulum