Self-steering under sails.pdf

SELF-STEERING UNDER SAIL

Autopilots and Wind-steering Systems

Peter Christian Förthmann

Content

1 The history of self-steering............................................................................................... 9

The first windvane steering system ................................................................................... 9

The first cockpit autopilot................................................................................................ 11

2 Windvane steering systems versus autopilots .............................................................. 12

Why autopilots? ............................................................................................................... 12

3 Autopilots ........................................................................................................................ 14

Cockpit autopilots for tiller steering ................................................................................ 15

Cockpit autopilots for wheel steering .............................................................................. 15

Inboard autopilots ............................................................................................................ 16

The three modules of an inboard autopilot ...................................................................... 16

Integrated systems ........................................................................................................... 21

The windvane transducer................................................................................................. 23

Power consumption ......................................................................................................... 23

Range of adjustment of an autopilot................................................................................ 26

The limits of autopilots.................................................................................................... 26

Autopilots for different purposes..................................................................................... 28

Choosing an autopilot ...................................................................................................... 32

4 Windvane steering systems ............................................................................................ 33

The Windvane.................................................................................................................. 33

The linkage ...................................................................................................................... 36

The rudder........................................................................................................................ 37

Damping .......................................................................................................................... 38

5 Types of system ............................................................................................................... 43

Windvane-only systems................................................................................................... 43

Auxiliary rudder systems................................................................................................. 43

Trim-tab-on-auxiliary-rudder systems............................................................................. 48

Trim-tab-on-main-rudder systems ................................................................................... 52

Servo-pendulum systems ................................................................................................. 53

Double rudder systems .................................................................................................... 78

The ultimate limits of windvane steering ........................................................................ 84

6 Choosing a System .......................................................................................................... 87

Materials .......................................................................................................................... 87

DIY construction ............................................................................................................. 89

Building a new boat ......................................................................................................... 89

Types of boat ................................................................................................................... 92

Swim ladders, swim platforms and davits ....................................................................... 99

Mounting a Windvane gear ........................................................................................... 101

Vessel size ..................................................................................................................... 101

Man overboard function ................................................................................................ 102

Summary........................................................................................................................ 103

7 Combination Systems ................................................................................................... 105

8 At a glance ..................................................................................................................... 107

System Comparison ....................................................................................................... 107

System comparison: autopilots versus windvane steering systems............................... 107

The ultimate limits of self-steering................................................................................ 108

9 The present situation .................................................................................................... 110

Trends ............................................................................................................................ 111

Practical tips .................................................................................................................. 112

Distribution.................................................................................................................... 114

10 Technical information................................................................................................... 115

Technical specifications of selected cockpit autopilots................................................. 115

The 12 types of windvane steering system .................................................................... 116

summary of the 12 types of system ............................................................................... 118

technical data of selected windvane steering systems ................................................... 120

11 A to Z of manufacturers................................................................................................ 121

Autopilots ...................................................................................................................... 121

Windvane steering systems ........................................................................................... 123

Appendix: Systems Manufacurers ................................................................................. 139

Autopilots ...................................................................................................................... 139

Windvane steering systems ........................................................................................... 141

Foreword

For some strange reason, most cruising sailors profoundly dislike steering by hand. The

prospect of spending hour after hour at the helm used to deter most people from long-distance

cruising. This is undoubtly the main reason why, until relatively recently, the number of

sailing boats venturing far afield was very small indeed. However, all that changed with the

advent of automatic pilots specifically built for yachts plus the development of efficient wind

operated self-steering devices. Suddenly, the chore of hand-steering was a thing of the past

and long ocean passages could be a pleasure – even on yachts with the smallest of crews.

Having made one circumnavigation of over 70,000 miles with an Aries and another of some

40,000 miles with a Hydrovane, I could not be accused of exaggeration if I state unreservedly

that one of the most important pieces of equipment on any cruising yacht is a wind-operated

self-steering gear.

Unfortunately, and surprisingly, this view is not shared by many cruising sailors. This is

primarily because as most of us have grown up with technology around us, we tend to take the

push-button mentality with us to sea. Steering a given course is easy to achieve by setting a

compass course and pushing a button on the autopilot, and, nowadays, this is what most

sailors prefer to do. It is usually on the first morning with flat batteries that the love-affair

with their favourite toy comes to an abrupt end. Having been forced to listen to countless

heart-rending stories on this very theme at the end of the ARC or similar trans-ocean rally, I

managed to persuade Peter Förthmann to come to Las Palmas before the start of the ARC to

talk to our participants about the pros and cons of self-steering. His talks and workshops

became an instant success, not only because he knows this subject better than anyone else in

the world, bus also because he always speaks generically about both wind-operated self-

steering gears and electronic autopilots. He never tried to sell his own products and, in this

way, enjoyed the interest and confidence of his audience.

I am therefore pleased, not only that he took my advice to write this long-overdue book,

but also that he managed to do it so fairly and objectively by giving all his competitors an

equal opportunity to make their products known. All existing systems are described in the

following pages, allowing the reader to make up his own mind. Many sailors agree that

Peter’s Windpilot is currently the best gear available. Being both the inventor and

manufacturer of this ingenious device, Peter has indeed shown that his name should stand

alongside those of his great precursors: Blondie Hasler, Marcel Gianoli, Nick Franklin. This

book confirms Peter Förthmann’s standing as the world authority on wind-operated self-

steering gears.

Jimmy Cornell

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