SELF-STEERING UNDER SAIL. Peter Foerthmann

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СКАЧАТЬ best be protected by ensuring that all power cables are well insulated.

      Extreme Sailing

      Autopilots are unable to steer in areas where North is uncertain. Extreme sailors in races like the BOC and Vendée Globe run into problems in the high latitudes of the South Pacific with the autopilot suddenly cutting out after losing its fix on North. Nandor Fa, skipper of the Hungarian yacht K & H BANK in one Vendée Globe (singlehanded non-stop around the world) received the following answer from the manufacturer of his Robertson system after faxing for help with his confused autopilot: “Please perform 3 complete circles in calm water within a few minutes - this will enable the compass to reorient itself”.

      

Nandor Fa onboard K & H Bank

      Given the chaotic sea conditions in the Southern Oceans this was not the most practical piece of advice. Only after several days of steering by hand did Fa come upon the idea of removing the compass and rotating it as gently as possible in his hand. Since then he has used Autohelm systems, which now have special GPS-supported software to help the compass maintain clear steering signals even when North is uncertain. The close collaboration between manufacturers and extreme sailors in events like the BOC and Vendée Globe ensures continued development of the systems. Virtually all the boats in these races are now steered by Autohelm.

      One result of this collaboration has been the development of stronger drive components for blue water use. Autohelm introduced the ‘Grand-Prix’ upgrade package for its 4000/6000/7000 series in 1996. The standard Delrin (plastic) load-bearing components in the drive are replaced with metal equivalents. Plastic, as several long-distance skippers have had the misfortune to discover, sometimes fails to measure up to the high stresses placed on drive components. For holidays and day sailing however, when extreme loads are rare, plastic components are perfectly adequate. Hydraulic systems are immune to overloading problems of this nature as they have no mechanical drive components (Autohelm 6000/7000 with hydraulic or hydraulic/linear drive, B&G NETWORK, HYDRA 2, Robertson, VDO).

      Autopilots for Different Purposes

      Holiday and weekend sailing

      Most sailors use their boats primarily at the weekend or for holidays, which partially explains the rapid spread of electric autopilots. Power consumption is not really an issue on one day trips and the quality of steering performance is also relatively unimportant since it is always possible to steer by hand if necessary. Sea conditions rarely impair steering quality as the majority of weekend sailors do not venture into exposed waters. Taking the helm in any case forms part of the fun for the average sailor, so the autopilot is really just a convenience. It sees to the tedious work (steering while under engine) and gives the crew the freedom to eat together, for example. Autopilots, at least the cockpit models, are also within the financial reach of the average sailor.

      The significance of a yacht’s autopilot grows with the length of the voyage. There will generally be no problem finding volunteers to steer on a shorter trip, but on a longer trip manual steering becomes tedious and the autopilot will eventually be called into action. The average weekend and holiday sailor has a good autopilot but makes relatively little use of it.

      Autohelm has devoted far more effort to the weekend and holiday sector than any other manufacturer and is the world-wide market leader; thanks in particular to its cockpit-mounted range the company has captured around 90% of the market.

      Coastal Sailing

      Coastal sailing in unprotected waters normally involves longer voyages. A small crew soon tires of steering and it is here that the steering quality of the autopilot starts to matter. Sea state and factors such as tidal streams, shallows, narrow channels and winds from forward of the beam all impair the performance of autopilots. Rough seas make life difficult for them and as the waves increase in height and frequency the limits of a particular system quickly become apparent. Not surprisingly, intelligent and adaptive systems cope better with trying conditions than factory-set units which cannot be adjusted.

      The general standard of equipment in this type of sailing is very high. The importance of good steering performance means that powerful inboard pilots connected directly to the main rudder are much more common; underpowered systems are soon exposed on the open sea. Although more powerful autopilots are inevitably hungrier, this rarely leads to battery problems since coastal sailing includes fairly regular motoring.

      Blue Water Sailing

      An autopilot stands or falls on its blue water performance. An underpowered system on the ocean reacts too slowly, too weakly and with too much delay to keep the boat on course, with increased yawing the result. The fear of losing steerage, of rounding up into the wind or worse and damaging the rig or boat, gives every sailor nightmares. If your autopilot is untrustworthy in a sea you could find yourself at the helm for a very long time.

      The choice of autopilot becomes a survival issue for short-, double- or singlehanded sailing: a thousand miles at sea is more than enough to reveal the gulf between theory and reality, and choosing the wrong system could jeopardise the whole voyage. This is evidenced by the large number of would-be passage sailors who, reminded of the enormous importance of good self-steering on the initial leg of their voyage, stop off at Vilamoura, Gibraltar or Las Palmas to fit back-up systems, buy spare parts or add a windvane gear to supplement their autopilot. It is no coincidence that companies like Hydrovane and Windpilot deliver so many of their windvane steering systems to these strategic European jumping-off points!

      Although autopilots are standard on blue water yachts, the limitations of the different models (underpowered system, mechanical failures) dictate that they do not in fact steer continuously. A certain amount of manual steering is therefore unavoidable, something which is not always pleasant for the person on watch and which disrupts life aboard. The performance of electric autopilots drops sharply as wind and waves increase, so heavy weather steering often falls to a human helm as well. He or she of course has the advantage of being able to see (and hopefully avoid!) breaking waves.

      Jimmy Cornell, organiser of races for long-distance recreational sailors, established in his debriefing after the EUROPA 92 round the world race that automatic systems steered for only 50% of the total time at sea. Manual steering was preferred the rest of time, either to improve speed and carry more sail area or because self-steering systems just were not able to cope with the conditions. Some crews simply did not trust their technology. Almost all the skippers used the autopilot when motoring through calms even if they chose to steer by hand when there was enough wind to sail.

      The combination of off-the-wind sailing and long following seas characteristic of blue water passage making sets the stiffest challenge to any autopilot. The need for quick and forceful corrective rudder movements drives up the pilot’s power consumption and saps away at the vessel’s energy budget. This once again highlights the fundamental importance of responsible energy planning for any vessel intending to rely solely on an autopilot. The average power consumption of the autopilots used in the EUROPA 92 race was approximately 4.9Ah (average boat length 42 to 50 feet).

      We must add at this juncture that the electromechanical reliability of autopilot systems still leaves something to be desired, particularly under the conditions likely in blue water sailing. This means in practical terms that sooner or later every autopilot is going to fail completely and manual steering will be unavoidable. One look at the list in the Las Palmas ARC office of the skippers requesting autopilot repairs is enough to set anybody thinking. Not surprisingly, bigger electric circuits with a larger number of components are more susceptible to gremlins, СКАЧАТЬ