In 1898 Joshua Slocum started it all by completing a three year circumnavigation, from Boston to Newport, RI covering 46,000 miles in his 37 foot, nine ton sailboat all by himself. He devised self steering systems by connecting lines from sails to his tiller. His boat Spray had a particularly long and straight shape with a similar keel which made it easier for the boat to stay on course - easier than would be for our modern hulls with their little keels and rudders.

After WWII the world's oceans started to see a growing fleet of independent adventurers exploring the earth for themselves from their little boats. These self made explorers readily adopted self steering devices for their boats. In fact, the prime reason that the trickle of explorers in the 1950s has become a full armada of pleasure seekers can be attributed to two devices: GPS and self steering.

The self steering is handled by both the electronic autopilots and the mechanical windvane driven self steering devices. Most experienced cruisers have both - an autopilot for motoring and mechanical self steering for sailing. A discussion of autopilots versus non-electronic self steering is found at the end of this paper.

For week-end sailors that make the transition to become off-shore cruisers there are decisions to be made about upgrading autopilots or acquiring a mechanical self steering. Like the around the world sailboat racers, experienced cruisers have learned that confidence in autopilots can only be achieved by investing heavily in quality - preferably with a back-up and infallible power generation systems. The lack of any electrical power requirements makes the self steering devices most appealing to the offshore sailor - no mysterious black boxes and no consumption of amp hours ..... and there is something symmetrical about a sailboat being guided by the wind and not dictated to by a pulsating electrical device.

TYPES OF SYSTEMS - Servo Pendulums, Auxiliary Rudders and Trim Tabs

There are a variety of types of devices available although most are either of the 'auxiliary rudder' or the 'servo pendulum' style. The 'trim tab' type of system is also worth note. The systems and some of the more common brands can be classified as follows:

• Auxiliary rudder - Autohelm, Hydrovane, Sailomat, Windpilot
• Servo pendulum - Aries, Cape Horn, Fleming, Monitor, Sailomat, Windpilot
• Trim tab - Auto Steer, Sayes Rig

There are numerous other brands available. To find them simply do a search on the web for "self steering" or "wind vane self steering".

Of all these units only the Hydrovane and Aries have their roots in the '60s with Hydrovane's founder, Derek Daniels, being the last of a generation of self steering pioneers when he retired in 2002.

HOW THEY WORK

Operation of Wind Vanes - All of the mechanical self steering systems use some sort of a vane which is like a little flat sail without any shape or curvature. Originally plywood was used but now many are made of synthetics or even sailcloth on an aluminum frame for greater size and strength. The vane is set in an 'on course' position with its leading edge pointed straight into the wind. Imagine holding a big piece of plywood up in the air. If one edge is faced directly into the wind then it is relatively easy to hold but as you gradually turn it sideways so that the wind blows against a larger and larger apparent surface then there is more and more force pushing against the plywood. That is how the vane functions. To maximize leverage the vane is usually fixed on a horizontal axis. As the vessel goes off course the vane is pushed over which causes the linkage to do the rest - as explained below.

Auxiliary Rudders - An auxiliary rudder system involves a completely separate rudder from the main rudder. Hence vessels with such units end up with two entirely separate steering systems - a most compelling virtue - an emergency steering system already in place. The technique is for the main rudder to be locked in a neutral position, or actually locked in a balancing position that compensates or eliminates any weather helm, and then the auxiliary rudder does all the steering. The deflection of the vane is the impulse that directs the rudder via various systems of linkage.

Examples of the differing methods to drive their rudders: The Autohelm uses a trim tab on a large unbalanced rudder. Its virtue is the ability to have the vane installed nearby but not directly attached to the drive shaft. The Hydrovane uses a balanced rudder and a particularly large vane with some unique linkage to get its power. Hydrovane has achieved a larger and more powerful vane by using an aluminum pipe frame covered with nylon cloth. Sailomat and Wind Pilot both have added to their product lines a servo pendulum system that powers an auxiliary rudder. A balanced rudder is a significant component of the systems of Hydrovane, Sailomat and Windpilot as it takes such little effort/power to cause it to move.

Strengths of the auxiliary rudder systems:

1. The vane is set pointing into the wind - it's leading edge to windward
2. The main wheel/tiller is locked off at the position that balances the boat for any weather helm
3. As the vessel goes off course the vane, in turn, deflects which causes the rudder to turn and bring the boat back on course

Strengths of the auxiliary rudder systems:

• A complete back-up steering system for emergency use
• Can be installed off-centre to accommodate swim platforms and ladders - except the servo pendulum units
• Less yaw due to immobile main rudder
• Fixed main rudder predetermines a 'balanced boat' as any weather helm is compensated for
• No tense lines through the cockpit
• Main rudder system is less prone to break-down as it would be used far less
• In collision avoidance situations it is easy to turn the wheel/tiller 'hard over'
• Suitable for most boats

Weaknesses of the auxiliary rudder systems:

• Appendage on the transom that adds to the boat length and is an obstacle when maneuvering in tight quarters
• Drag - another rudder or two in the water - creates more wetted surface

Servo Pendulum Systems - These units are unique for their blade or paddle that seems to reach out in the water. The off-course deflection of the vane, through the leverage of some linkage or gears causes this paddle/blade in the water to twist. That twisting presents a face of the paddle to the water flowing by forcing the paddle to swing with force to one side or the other. The motion of the paddle causes connecting lines to the main steering wheel/tiller to move which in turn causes the main rudder to change course. These systems require somewhat intricate installations involving a number of blocks that are positioned to minimize friction for the connecting lines to the wheel/tiller. The tensioning of those lines is critical as is the tuning of the systems.

To summarize that connectivity:

1. by going off course the vane deflects
2. causing the paddle/blade in the water to turn
3. the passing water then pushes the paddle/blade face to one side
4. the swinging sideways of the paddle/blade pulls on connecting lines to the wheel/tiller
5. causing the wheel/tiller to move
6. hence the rudder moves to alter course

Strengths of servo pendulum systems:

• Power is derived from the boat speed through the water - producing great power as the boat gains speed
• Break-away feature of most paddles
• Paddles are usually removable when not in use

Weaknesses of the servo pendulum systems:

• Tensioning and tuning of the connecting lines that can suffer from stretch, binding or chafe
• Obstacle in the cockpit of those tensioned connecting lines
• Breakage of the paddle/blade from hitting floating objects as it swings from side to side - most units have break-away features to accommodate such pressure or impact
• Can have difficulty in light airs - friction can vary enormously, especially in the types of rudder mechanisms - result can be non-functioning in light airs due to insufficient power - especially downwind - works better on boats with balanced rudders and lighter/faster boats
• Appendage on the transom that adds to the boat length and is an obstacle when maneuvering in tight quarters
• Drag of the paddle in the water

The servo pendulum systems are not adaptable to all sailboats. Some of the situations that are not suitable are:

• Vessels with hydraulic steering
• Center cockpits or when the connecting lines must be very long or travel an indirect route to the wheel/tiller - friction and tensioning become more challenging with the addition of more turning blocks or longer lengths of line
• Steering wheels/tillers that require considerable strength to move
• Wheels/tillers with too few or too many rotations required to move the rudder its full radius

Trim Tabs - A trim tab is a mini rudder that is attached to a larger rudder. Through the windvane and leverage via certain linkage, the trim tab is caused to move in the opposite direction than the desired direction for the larger rudder. So as the trim tab turns it forces the rudder to which it is attached to move in the opposite direction - effectively, it drives the larger rudder over. Trim tabs prove to be very simple and powerful although they do create a certain amount of drag as the face of the tab (mini rudder) can be nearly 90 degrees to the direction of the rudder to which it is attached. The Sayes Rig is a fairly large rudder/trim tab that is connected to the main rudder by a hoop that is installed on the main rudder. The Auto Steer is meant for vessels with transom hung rudders. The Autohelm is a trim tab onto an auxiliary rudder whose vane may be located some distance from the rudder - attached only by cables.

KEY ISSUES

Sensitivity and Power - All the above systems do the job - to varying degrees. To differentiate between the various systems an assessment must focus on their 1) sensitivity 2) power and 3) durability. The challenge of the design of a system is to utilize the right mixture of power and sensitivity. The requirements of the systems vary with the wind speed and for each point of sail. A boisterous sea can also add challenges as it throws, with great force, the boat and its sensitive vane, in all directions. The de-sensitizing of self-steering is called 'damping'. The damping is defined as a virtue peculiar to windvane self-steering - an ability to slow the rate of course change when making course corrections - hence not over steering in order to produce a gentle return to the desired course. The 'S' pattern of the wake tells the story. Ideally a good helmsman strives to keep the vessel heading in a straight line. In heavy seas it is impossible to achieve anything like a straight course but, in those conditions, the capacity of the steering system to 'automatically' apply the right amount of steerage with appropriate force is of paramount need. Excess power or correction exacerbates the need for an even stronger reaction in the other direction and so on. Insufficient power is not even workable. Neither brute power nor extreme sensitivity are the answer.

In conclusion, the system must be:

• adjustable to varying degrees of 'damping'
• adequately powered in light and heavy air

Durability - Second only to the vessels' ability to float is the importance of steerage. Bad weather in the open sea puts enormous demands on the entire vessel but especially on the steering systems. It is no time for a breakage - but that is exactly the time when the weakest link will give way - and a time when the crew is least able to deal with it!

MAINTENANCE AND TROUBLESHOOTING

Friction - In light winds the amount of friction in a system determines at what point it becomes effective or ineffective. The servo pendulum systems have much more potential and inherent friction. The lines and turning blocks should be cleaned of salt and grit and regularly re-tensioned - but not over tensioned as that can cause binding. Blocks should be of the higher quality with roller bearings. Not much can be done about the boat's actual steering mechanism although it should be reviewed to see if there is unnecessary stiffness. Auxiliary rudders have much less potential for friction with the Hydrovane having perhaps the least of all as it does not have any of the external paraphernalia as the others: lines, cables, trim tabs or paddles in the water.

Damage from Collision - All devices strapped onto transoms are vulnerable to collision - with other boats, docks, pilings etc. The rudders and blades in the water are also exposed to any passing floating debris and fishnets. The servo pendulum blades have proved to be the most vulnerable as they swing from side to side - away from the protection of the keel and main rudder. For that reason they are generally designed with a break-away feature.

Breakage and Wear - Each product will have certain parts that are either vulnerable to breakage and wear or prone to fail or simply fall off and be lost overboard. The suppliers often provide a 'spares kit' that includes all those items. It is worth enquiring about the durability of vanes, rudders, paddles, gear mechanisms and any other items.

Finally, perhaps the greatest problem comes from installing too small a unit for a given boat in order to cut costs. Not only will performance be unsatisfactory, but the unit will be overstressed and likely to fail. It is far better to err on the conservative side, especially if you are considering ocean crossings. Steering by hand on long passages becomes a monumental chore.

Balancing a boat - Despite the dramatic force amplification achieved hydrodynamically, the end forces generated by self steering devices are still not that powerful, especially in light winds and at slow boat speeds. No self-steering apparatus will operate effectively unless the boat is balanced first. This is largely a matter of sail trim, although where an auxiliary rudder is used the main rudder will be locked off in such a way as to correct for helm imbalance e.g., weather helm.

Most boats will self steer hard on the wind without a self-steering device. But as the boat comes off the wind, balance is harder and harder to achieve. On a beam reach it may be necessary to sacrifice optimum sail trim - e.g., by letting the mainsail luff somewhat - in order not to overpower the self-steerer.

When broad reaching and running, the more the center of effort can be concentrated in the headsails the easier the boat will be to control - eg - either no main (or mizzen) with only twin jibs set or a 'wing-on-wing' configuration with main sheeted out as far as possible and the jib poled out to the weather side. Since apparent wind speed is much reduced when running, the wind vane exerts less force than on any other point of sail; combine this with the fact that, when headed downwind, sea conditions can be unrully, then it is easy to see that the self steering system will need all the help it can get. Downwind sailing in ocean swells is the acid test of any self-steering device.

Yaw. A self-steerer reacts to a change in course and can never anticipate wind shifts or wave action. It is therefore, a built in tendency to cause the boat to yaw from side to side around the course line. The further the boat is off the wind, the greater the tendency to yaw. Better systems have a degree of yaw damping capability. The gear is designed in such a way that as the boat's rudder or auxiliary rudder turns in response to 'instructions' the force exerted is lessened or 'dampened' to achieve a gentler return to course. An 'undampened' steerer will effectively have only an 'on' or 'off' mode which results in more violent course corrections - hence more yaw. But even so, no self-steering will hold a downwind course in following or quartering seas without a fair degree of yawing - just as no helmsman can.

ADVANTAGE OVER AUTOPILOTS

When comparing a good autopilot to a good windvane self-steering device what are the separators?

An expensive autopilot is a most impressive piece of machinery. Push a button and watch it go. There is nothing easier - supposedly. The most rigorous test of autopilots is done every year or so by the around the world ocean racers. A decade or so ago the windvane got instant fame when the arriving fleet in Australia, in frustration over the non-performance of their autopilots, in masse ordered self steering systems for the next leg of the race. Since then the autopilots have made vast improvements and the boats themselves have become flying carpets that can average speeds of over 20 knots for long periods of time. A boat that accelerates from a hull speed of 8 knots to a constant surfing speed of 20+ knots is beyond the range of any of the mechanical devices - not to mention the sail loads that they carry. Of more importance is the method that these racers use to manage their most critical self steering - and that is to have multiple autopilots and generators. The norm for them now is to have as many as two autopilots operational and at least that many as spares. As well, they require a totally redundant set-up to provide electricity. This would include at least one if not two generators as well as the main engine. The proper functioning of an autopilot means not only that its black box and mechanics must stay healthy but that the supporting power generating systems must as well be fully operational. A single glitch in any one of thousands of parts can stop the autopilot: fuel pumps, fuel filters, starter, alternator, regulator, batteries, engine valves and on and on. The point is that reliability can only be achieved with considerable redundancy - and enormous cost.

Today, as local sailors graduate to become offshore cruisers there is a tendency to stick with the devil they know - the autopilot. Certainly there are many circumnavigators who have happily sailed the world relying on only an autopilot for self steering. Too bad that they have never come to know the independence that can be gained when using a mechanical self steering device ...... something about teaching an old dog new tricks.....or maybe they are not that comfortable sailing and prefer to rely on the iron staysail.

A mechanical self steering device is blissfully independent of all other systems and its very simple parts carry on in a most un-mysterious fashion. So the real difference between autopilots and mechanical self steering is simplicity, reliability and lack of power consumption.....

And, of course, there is something symmetrical about a sailboat being guided by the wind and not dictated to by a pulsating electrical device.