I like this "clever cheap" self steering option a lot, as a backup is case of electric pilot's circuit board or electronic compass failure. Instead of driving a car wash motor, it could also be used to drive a tiller pilot's native motor.

Also, native autopilot's electronics may be able to control a car wash motor, as a backup in case of autopilot's mechanical faiture...

Hi Gary,

Gary King wrote:Saw this on a home built 60' boat yesterday. 

A car’s windscreen wiper electric motor attached to the helm wheel by belt. It is activated by a small windvane weather cocking on the pilothouse roof, the vane’s shaft comes inside and a tab bolted to it hits electrical switches either side of it. 

The vane rotates left, it hits the left switch, the motor spins one direction, right the other. A solenoid was used to switch on the motor.

The owner says it works perfectly except downwind in lighter breezes, which is a complaint for any wind vane.

So there's no negative feedback built in, no proportionality to the response; it relies on the boat's directional stability. That's why it won't steer downwind. That's why commercial autopilots have some kind of fancy electronic circuitry to make the angle off course proportional to the amount of helm applied.

The auxiliary rudder

 

There is a third sort of windvane gear that in some cases makes sense to fit: The auxiliary rudder.

 

If the not-too-big boat has an inboard rudder and there is room on the stern to fit a second one, a perfectly balanced aux. rudder, about ²/₃ or ¾ the area of the main rudder , will do the trick.

 

 

The aux. rudder has some advantages:

·         Above all, it is very easy to make for any eager amateur, compared to a servo pendulum system.

·         One also gets a fully operational spare rudder in the aux. rudder.

·         If the boat lacks directional stability, then locking the main tiller would rectify this. In other words, the boat will be directionally stable at sea, but still be easy to manoeuvre in harbour.

·         The main rudder can also be locked after offsetting it a bit to balance out any weather or lee helm, making the job easier for the aux rudder.

 

 

The aux. rudder is of course controlled by a windvane, either directly by a biggish horizontal shaft vane, or via its own trimtab, driven by a smaller windvane (a vertical shaft vane will  generally do)

 

The windvane guru, Bill Belcher has shown some good examples of aux. rudders.

 

 

Cheers, Arne

Saw this on a home built 60' boat yesterday. The trick for self steering is to amplify the forces from the wind vane. A pendulum use an paddle in the water, the other type uses a trim tab on the rudder. This one uses a vane and electricity, but its very cheap to make.