- Self-steering gear
Self-steering gear is equipment used on ships and boats to maintain a chosen course without constant human action. It is also known by several other terms, such as
autopilot(borrowed from aircraft and considered incorrect by some) and autohelm (technically a Raymarinetrademark, but often used generically). Several forms of self-steering gear exist, divided into two categories:
Electronic self-steering is controlled by electronics operating according to one or more input sensors, invariably at least a magnetic compass and sometimes wind direction or GPS position versus a chosen waypoint. The electronics module calculates the required steering movement and a drive mechanism (usually electrical, though possibly hydraulic in larger systems) causes the rudder to move accordingly.
There are several possibilities for the interface between the drive mechanism and the conventional steering system. On yachts, the three most common systems are:
# Direct drive, in which an actuator is attached to the steering quadrant, at the top of the rudder stock inside the boat. This is the least intrusive method of installation.
# Wheel mounting, in which a motor is mounted near the steering wheel, and can be engaged with it when in use. This typically involves either a belt drive or a toothed gear-ring attached to the wheel itself, and is a common option for retro-fitted installations on yachts with a wheel.
# Tiller-pilots are usually the only option on smaller vessels steered with a tiller. They consist of an electrically driven ram which is mounted between the tiller and a fitting on the side of the cockpit. Some are entirely self-contained, needing only a power supply, while others have the control unit separate from the actuator. These are quite popular, as they are maintenance-free and easy to install. ["The Sailors Handbook" by H.C. Herreshoff]
Depending on the sophistication of the control unit, electronic self-steering gear can be programmed to hold a certain compass course, to maintain a certain angle to the wind (so that sailing boats need not change their sail trim), to steer towards a certain position, or any other function which can reasonably be defined. However, the amount of power required by electrical actuators, especially if constantly in action because of sea and weather conditions, is a serious consideration. Long-distance cruisers, who have no external source of electricity and often do not run their engines for propulsion, typically have relatively strict power budgets and do not use electrical steering for any length of time. As the electronic autopilot systems require electricity to operate, many vessels also make use of PV solar panels or small
wind turbines on the boat. This eliminates extra pollutionand cut costs. ["The Sailors Handbook" by H.C. Herreshoff]
Mechanical or "wind vane" self-steering started out as a way to keep model sail boats on course. The first time that it was used to cross an ocean was on a motorboat. The most widespread form of self steering, the servo pendulum principle (introduced by Herbert "Blondie" Hasler) uses power derived from the motion of the boat through the water to hold a constant angle to the wind with the use of the boats main rudder. Offshore, the wind direction is relatively stable, so over a number of hours this results in a reasonably constant compass course, and also means that the sails need not be adjusted. At present, new wind vane self-steering systems are present which incorporate a
compass, to remove the disadvantage of having the boat's current coarse changed when the wind has shifted. Mechanical self-steering can be complicated to set up, so it is typically used only for long-distance sailing where the same course is maintained for long periods. Many boats fitted with mechanical self-steering also carry an electrical autohelm for use over shorter periods where it is not worth setting up the wind vane.
Mechanical self-steering gear is made by a number of manufacturers, but most share the same principle. A narrow upright board, the wind vane, is rotated so that with the boat traveling in the desired direction it is edge-on to the wind. The wind vane is held upright by a small weight below the pivot, but if the boat turns so that the board is no longer edge-on to the wind it will be blown over to one side as the extra surface area is revealed. This movement is transmitted by a series of linkages to a second blade in the water. In the simplest devices for very small boats, this blade acts directly as a secondary rudder, and steers the boat back onto the proper course. The force provided by the wind vane, however, is not sufficient to make this system work with larger loads, and hence a so-called servo pendulum system is used:
As the blade described above turns, the pressure of water moving past it causes it to swing out sideways on the end of a pivoted rod. The length of this rod and the speed of the water means that a considerable force is available at the top end of it, sufficient to change the course of much larger boats. This is achieved either by a connection to the main wheel or tiller (typically involving a complex arrangement of lines and blocks rigged around the stern of the boat) or by fixing the main steering in place and equipping the self-steering gear with its own rudder. Once the boat has moved back to its correct course, the wind vane stands up again as it is no longer blown over by the wind.
If the sails are trimmed correctly and the device is properly set up, wind vane self-steering is very effective. Some experimentation and judgment is usually needed, however, to determine the proper settings for a given vessel and steering mechanism. In addition, wind vanes perform poorly in very light winds, as the forces needed to operate them are much reduced. The same applies when traveling downwind, as the apparent wind speed is reduced by the speed of the boat.
As well as their requirement for power, many long-distance cruisers observe that electronic self-steering machinery is complex and unlikely to be repairable without spare parts in remote areas. By contrast, the often agricultural-looking mechanism of a wind vane gear offers at least the possibility of an improvised repair at sea, and can usually be rebuilt on land using non-specific parts (sometimes plumbing parts) by a local welder or machinist.
The topic of single handed sailors sleeping and hence not maintaining a 'proper watch for safe navigation' continues to be much discussed. Although this practice appears to be in contravention of maritime law, there has so far been no attempt to prevent it. A pragmatic approach is that such individuals are at least endangering only themselves, since the large cargo vessels that may collide with them while they are asleep typically are not even aware that they have hit something. In addition, radar alarms and the sheer vastness of the ocean mean that the problem is more one of theory than of practice.
A related device has been used on some
windmills, the fantail, a small windmill mounted at right angles to the main sails which automatically turns the heavy cap and main sails into the wind, (invented in England in 1745). (When the wind is already directly into the main vanes, the fantail remains essentially motionless.)
A popular source on contemporary windvane technology is [The Windvane Self-Steering Handbook] [http://www.bookstore.mcgraw-hill.com/product.php?isbn=0071434690] (International Marine/McGraw-Hill--2004), authored by circumnavigator and Somali piracy survivor Bill Morris. One particularly valuable contribution of Morris's book is his coverage of the variety of alloys used in vane gear manufacturing. Morris admits to his practice of setting a kitchen timer for a half hour at a time and sleeping while the windvane steering device controls the helm, even in head winds of 25 to 35 knots. In a recent interview, he said he once narrowly missed being hit by a huge freighter while sleeping on his sail up the Red Sea. Morris points out, "An autopilot wouldn't have made any difference in this case. If I had been using an electronic autopilot, that freighter still would have been there. I made a choice to sail two-thirds of my circumnavigation single-handed, and I accepted the risks that came with that decision. I guess fate was on my side."
Manufacturers of Electronic Self-Steering gear
Raymarine Marine Electronics- Most prolific manufacturer of self-steering systems. * [http://www.raymarine.com Official Website]
* [http://www.alphamarinesystems.com Alpha Marine Systems] - Maker of the "3000" and "Spectra" product lines, specially designed for offshore and sail-racing yachts.
* [http://www.simrad-yachting.com/Products/Leisure/Autosteering/ Simrad Yachting]
Manufacturers of Windvane Self-Steering gear
* [http://www.ariesvane.com/index.html Aries] Rebuild kits and spare parts service for original Nick Franklin's Aries self-steering gears
* [http://www.selfsteer.dk/ Aries] Aries servo-pendulum type windvane gear from Denmark. Heavy aluminium alloy construction
* [http://www.caphorn.com/superlatives.htm Cape Horn] Canadian servo-pendulum windvane system. Different modells: integrated without stearing lines or outboard with stearing lines. Stainless steel construction
* [http://www.flemingselfsteer.com/products.htm Fleming] Different types servo-pendulum windvane systems; operating with main rudder or on an independent auxiliary rudder. Stainless steel alloy construction
* [http://www.hollandwindvane.com/index.htm Holland Windvane/Bouvaan] A professional DIY selfsteering servo-pendulum type windvane kitfrom Holland. Stainless steel construction
* [http://www.hydrovane.com Hydrovane] Auxiliary rudder system with windvane without servo assistance. Manufactured in England
* [http://www.mistervee.com/ Mister Vee] Supplier of light weight (<8kg/18lbs) self steering systems for self assembly, very suitable for smaller boats
* [http://www.sailomat.com Sailomat] Servo-pendulum windvane system, aluminium construction
* [http://www.south-atlantic.com.ar South Atlantic Self steering systems] Servo-pendulum windvane system in 2 size. Aluminium construction
* [http://www.vectavane.com VectaVane] Simple servo-pendulum windvane for tiller-steering on smaller sailboats
* [http://www.mindspring.com/~waltmur/Self-Steering/ Walt Murray's designs] DIY Self steering systems on a shoe string budget
* [http://www.windpilot.de Windpilot] Different types from Germany: Pacific Light (13 kg) and Pacific servo-pendulum windvane systems; Pacific Plus servo-assisted auxiliary rudder gear. Aluminium pressure diecasting construction
* [http://www.windsteuerung.de/index.html Wind-Autopilot im Eigenbau] DIY Self steering systems
* [http://www.bluemoment.com/selfsteering.html Singlehanded sailing discussion of self steerng.]
* [http://www.shorthandedsailing.com/forum/6 Forum on self steering] at the * [http://www.shorthandedsailing.com shorthanded sailing] community
* [http://www.windpilot.de/Grafiken/pdf/bookeng.pdf Selfsteering under Sail by Peter Förthmann] Downloadable book
Wikimedia Foundation. 2010.
См. также в других словарях:
self-steer|ing — «SEHLF STIHR ihng», adjective. designed to keep a boat or aircraft on a fixed course: »self steering gear … Useful english dictionary
Steering — For other uses, see Steering (disambiguation). Part of car steering mechanism: tie rod, steering arm, king pin axis (using ball joints). Steering is the term applied to the collection of components, linkages, etc. which will allow a vessel (ship … Wikipedia
Gear — For the gear like device used to drive a roller chain, see Sprocket. This article is about mechanical gears. For other uses, see Gear (disambiguation). Two meshing gears transmitting rotational motion. Note that the smaller gear is rotating… … Wikipedia
Top Gear challenges — are a segment of the Top Gear television programme where the presenters are challenged by the producers, or by each other, to prove or do various things related to automobiles. Contents 1 Novelty/stunt challenges 2 Challenge reviews 3 How hard… … Wikipedia
Herbert Hasler — Lt. Col. Herbert George Blondie Hasler DSO OBE (27 February 1914 – 5 May 1987) was a distinguished Royal Marines officer in World War II, responsible for many of the concepts which led to the post war incarnation of the Special Boat Service, a… … Wikipedia
Sunday Times Golden Globe Race — The Sunday Times Golden Globe Race was a non stop, single handed, round the world yacht race, held in 1968 ndash;1969, and was the first round the world yacht race. The race was controversial due to the failure by most competitors to finish the… … Wikipedia
Single-handed sailing — The sport of single handed sailing is sailing with only one crewmember (ie. only one person on board the vessel). The term is usually used with reference to ocean and long distance sailing, and particularly competitive sailing. Terminology In… … Wikipedia
Man overboard — For other uses, see Man Overboard (disambiguation). Signal flag Oscar indicates man overboard … Wikipedia
Autopilot — An autopilot is a mechanical, electrical, or hydraulic system used to guide a vehicle without assistance from a human being. Most people understand an autopilot to refer specifically to aircraft, but self steering gear for ships, boats, space… … Wikipedia
Donald Crowhurst — Donald Crowhurst, pictured just before setting out in the Sunday Times Golden Globe Race in 1968. Donald Crowhurst (1932–1969) was a British businessman and amateur sailor who died while competing in the Sunday Times Golden Globe Race, a single… … Wikipedia