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Self-steering gear is equipment used on sail boats to maintain a chosen course or point of sail without constant human action. [1]
| | This article needs additional citations for verification .(February 2020) |
Self-steering gear is equipment used on sail boats to maintain a chosen course or point of sail without constant human action. [1]
Mechanical or "wind vane" self-steering started out as a way to keep model sail boats on course. Before the advent of radio control, model yacht racing (started before WW1) was typically contested on long narrow ponds, and the number of stops along the banks was counted as a penalty in the final result. Initially a system of counterweight on the tillers was devised to compensate for the weather helm when the model boat heeled in a gust. These crude systems evolved in a more sophisticated system called Braine Gear after its inventor, George Braine. [2] The Braine steering gear was a fine-tuned system of quadrant on the rudder stock driven by the tension of the mainsail sheet and damped by a rubber band. A more sophisticated system called the vane gear was later devised, it relied on a small vane or airfoil driving the main rudder via an adjustable system of clockwork gears. It was very similar to the later vane driven autopilots seen on transatlantic yachts such as Blondie Hasler's self steering rudder. Some transatlantic singlehanded sailors used a crude form of self steering devices to cross the Atlantic Ocean in the 1920s and 1930s, the most notable being Frenchman Marin Marie (Paul Marin Durand Couppel de Saint Front) who crossed the Atlantic twice in the 1930s, first on a sailing yacht called Winnibelle II and secondly on a motor pinnace called Arielle.
Self steering aboard Winnibelle II on its Atlantic crossing from Douarnenez, France, to New York in 1933 was somewhat similar to a Braine gear, using twin jibs (Trinquettes jumelles) with their sheets connected to the rudder via an array of blocks and lines. The long keeled Winnibelle II was perfectly stable on course on close-hauled or beam reach points of sailing but the self steering twin jib system could take over in the trickier downwind broad reaches and running points of sailing.
On the small motor pinnace Arielle, a 13-metre boat propelled by a 65HP French made Baudouin diesel engine which sailed from New York to Le Havre in 1936, the task of steering a motor boat in the Atlantic swells was more daunting. Arielle had two rudders; the main one under the hull, in the propeller race, was for manual steering and the smaller auxiliary rudder was transom mounted. This auxiliary rudder could be mechanically driven by a special wind vane mounted atop of the coachroof consisting of two rectangular airfoils set at an angle on a vertical axle and balanced by a counterweight. It was simple and worked quite well, but could not steer the boat in very light breezes or flat calm.
While Marin Marie was fitting out Arielle in New York he was approached by a French inventor named Casel who offered to fit an electrical autopilot of his invention, free of charge. The Casel autopilot was using the then revolutionary photoelectric cells and a system of light and reflecting mirrors on the magnetic compass rose. Its principle is somewhat similar to modern day electronic autohelms, excepting the modern flux-gate sensor for autopilots system. The Casel autopilot, which included an array of green, red and white telltale control lights, used an electric motor to act on the main rudder. Though its basic principle was sound and was useful in some sections of the passage, it proved to be somewhat too lightly built for a wet vibrating little boat and was trouble ridden. Marin Marie, though appreciative in some occasions generally loathed the temperamental device, specially when he discovered that Casel had inadvertently hidden his stores of Bordeaux wine in the autopilot compartment, unwillingly condemning him to a teetotal Atlantic crossing of some 20 days.
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:
Depending on the sophistication of the control unit (e.g. tiller pilot, steering wheel attached chartplotter, ...), 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, which 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 photovoltiac (PV) solar panels or small wind turbines on the boat. This eliminates extra pollution and cuts costs. [3]
The main goal of a mechanical self-steering gear is to keep a sailboat on a given course towards the apparent wind and to free the helmsman from the steering job. An advantageous side effect is that the sails are kept in optimal angle towards the apparent wind and deliver optimal propulsion force by that. Even in sailboats running under engine, the self steering gear can be used to keep the boat heading into the wind to easily set or change sails (exception: sheet-to-tiller principle).
As wind direction sensors are used
a) a wind vane mounted on an axis being tilted more or less towards the horizon (wind vane self-steering)
b) the pressure of the wind in the sail(s) and by that the force on the sheet (sheet to tiller self-steering).
The different mechanical principles of coupling a change in apparent wind direction mechanically with a course changing actuator (rudder) can be roughly grouped:
Mechanical self-steering units are made by a number of manufacturers, [4] but most systems produced today share the same principle (servo pendulum rudder, see below). As well as their requirement for electric power, many long-distance cruisers observe that electronic self-steering machinery is complex and unlikely to be repairable without spare parts in remote areas[ citation needed ]. By contrast the 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[ citation needed ]. To minimize the speed loss by the self steering gear it is essential to have the vessel's sails balanced with little load on the rudder before any attempt is made to engage the self steering. With the sails are trimmed correctly, the force-balance of the servo oar and the main or auxiliary rudder is minimized that way, that the lowest angles of attack of rudder and servo oar towards the water flow are achieved. Some experimentation and judgement is usually needed, however, to determine the proper settings for a given vessel and steering mechanism. A popular source[ citation needed ] on contemporary windvane technology is The Windvane Self-Steering Handbook. [5] One particularly valuable contribution[ citation needed ] 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."
In former trim-tab servo systems, the pivot movement of the servo blade around its vertical axis has been carried out by a trim tab servo tab, which however costs some force due to the fact, that the trim tab is moved in the opposite direction to turn the servo blade. The same holds for a trim tab, which is mounted at a big distance behind the ship's rudder, connected to it at its upper and lower end. This construction is called "The Saye's Rigg". Another version of wind vane self steering on sail boats is known as the vertical axis vane and usually, because of the inferior steering force output compared to servo pendulum devices it makes use of a trim tab hung off the rudder to control the course of the boat. The vane spins at right angles to the ground and can lock to the trim tab in any desired position, as the boat falls off the wind the vane will be turned by the wind and will take the trim tab with it which in turn causes the rudder to move in the opposite direction and thus corrects course. Generally self steering like this, with a trim tab can only be used on boats with transom (or aft hung double enders) rudders as the trim tab needs to be mounted directly to and aft of the rudder to produce the desired effect, and of course has to be controlled even as the rudder swings side to side. This is typically accomplished by use of a slotted bar in which the connection to the vane assembly can slide in as the rudder turns. These self steering systems are generally simpler and are thus easier to set and adjust course as they do not make use of lines controlling the rudder but control it more directly through solid linkages. [6] 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.)
Only few manufacturers have been successful with systems that operate an auxiliary rudder directly from the windvane (non-servo systems: Windpilot Atlantik, Hydrovane); the picture of the windvane shown uses this principle with the large fabric vane on a vertical axis (the use of wind vanes with a nearly horizontal axis is used predominantly).
The most widespread form of self-steering, the servo pendulum, was introduced to cope with the power required to operate a larger rudder and was a successor to the servo trim tab principle (introduced by Herbert "Blondie" Hasler). Common to all servo pendulum rudder (oar, blade) systems is the fact, that the speed of the boat through the water is used to amplify the small force coming from the wind vane in order to be able to turn the rudder. The servo blade can be turned in its vertical axis and is hung like a pendulum. When it is turned around its vertical axis, the water flow initiates a sideways force on the blade area, and the forceful swing movement to the side is used to act on a rudder (ship's rudder or auxiliary rudder being integrated in the system). A narrow upright board, the wind vane, is mounted on a nearly horizontal axis carrier that is itself rotated around its vertical axis so that with the boat traveling in the desired direction the vane is vertical and edge-on to the wind. The wind vane is balanced 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 blade (or oar) in the water, so that the oar is turned around its vertical axis, when the wind vane rotates from its neutral position. 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. An immersed area of 0.1 m2 at 1 m lever length at a boat speed of 2.5 m/s (about 5 knots) and 5° angle of attack already generates a moment of 180 N⋅m, when the oar has a NACA0012 profile. [7] The steering force of the servo oar is transmitted to the main rudder typically involving an arrangement of two lines and four or more rolls to guide the steering ropes to the helm or the steering wheel.
Modern servo pendulum self-steering devices with optimized transmission and low friction mechanics are more and more used for day sailing and cruising; formerly being used mainly for long distance ocean passages. The increased low wind capabilities of optimized, modern devices enable downwind steering down to 1.3 m/s apparent wind and 1.5 kn of boat speed [8] [9] – properties that make an electronic steering device nearly redundant and enable crossing the doldrums under wind vane self-steering. An increasing number of long distance regatta sailors are using wind vane self-steering because the sails are always kept in optimal angle towards the wind, and hence the speed of the boat is kept at the possible maximum.
The mathematical description of the horizontal windvane servo self-steering covers the relation of a course error to a steady-state rudder angle to correct for the course error. The dynamics are described by force and momentum coupling equations. [10] [11] Mainly three different mechanical transmission principles are in use: Murray slide-block joint, 90° bevel gear, Z-shaft, which due to their geometry have different steering force changes by course error change. [12]
In cases, when a pure servo pendulum self-steering gear is not usable (hydraulic rudder gear, very big force needed to turn the rudder), auxiliary rudder systems are used. They consist of a servo pendulum rudder coupled directly to an auxiliary rudder which is part of the self-steering system. The main rudder in such case is used to "trim" the main course and the self-steering gear steers "around" that main course according to the changes of the apparent wind.
Aside of the widespread mechanical self-steering through a wind vane being mechanically coupled to the rudder or a servo pendulum rudder, there is a mechanical self steering principle called "sheet-to-tiller". Rollo Gebhard crossed the Atlantic in his 5.6 m long Solveig using such a method. The sheet-to-tiller self-steering consists of a connection between the spring-loaded tiller and a sheet using the force of the wind in the sail to steer the boat.
For quite a long time there was little development in the self steering systems that were available commercially. Most new developments came in the form of self-build systems. Crucial roles were played by Walt Murray, an American who published his designs on his website. [13] and Dutchman Jan Alkema who developed a new windvane, the so-called up side down windvane (USD for short, commercially available from only two brands) and a new kind of servo pendulum system that could be fitted to boats with a transom hung rudder. For this last invention Jan Alkema was rewarded the John Hogg-Price from the AYRS ( Amateur Yacht Research Society) in 2005. Jan Alkema published a lot of his inventions on Walt Murray's website. [13]
Joern Heinrich added in 2010 a mechanism [14] using the roll angle of the boat in downwind situation for a correctional servo oar angle of attack which increases course stability and lowers the risk of broaching in following seas. [15] Joern Heinrich also published a mechanism [16] which uses a fin in the water to compensate for the apparent wind change during the acceleration/deceleration of multihull yachts with larger speed potential like catamarans and trimarans in gusts. Heinrich applies his own parametric simulation software VaneSim [17] to optimize windvane self-steering devices according to boat properties.
Some notable self-steering sailboats include:
Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the water, on ice (iceboat) or on land over a chosen course, which is often part of a larger plan of navigation.
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium. On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane. A rudder operates by redirecting the fluid past the hull or fuselage, thus imparting a turning or yawing motion to the craft. In basic form, a rudder is a flat plane or sheet of material attached with hinges to the craft's stern, tail, or after end. Often rudders are shaped so as to minimize hydrodynamic or aerodynamic drag. On simple watercraft, a tiller—essentially, a stick or pole acting as a lever arm—may be attached to the top of the rudder to allow it to be turned by a helmsman. In larger vessels, cables, pushrods, or hydraulics may be used to link rudders to steering wheels. In typical aircraft, the rudder is operated by pedals via mechanical linkages or hydraulics.
Steering is the control of the direction of locomotion.
Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude.
Boat building is the design and construction of boats and their systems. This includes at a minimum a hull, with propulsion, mechanical, navigation, safety and other systems as a craft requires.
A trolling motor is a self-contained marine propulsion unit that includes an electric motor, propeller and control system, and is affixed to an angler's boat, either at the bow or stern. A gasoline-powered outboard used in trolling, if it is not the vessel's primary source of propulsion, may also be referred to as a trolling motor. The main function of trolling motors is to keep the boat running at a consistent, low speed suitable for trolling. Trolling motors are often lifted from the water to reduce drag when the boat's primary engine is in operation.
A tiller or till is a lever used to steer a vehicle. The mechanism is primarily used in watercraft, where it is attached to an outboard motor, rudder post or stock to provide leverage in the form of torque for the helmsman to turn the rudder. A tiller may also be used in vehicles outside of water, and was seen in early automobiles.
An azimuth thruster is a configuration of marine propellers placed in pods that can be rotated to any horizontal angle (azimuth), making a rudder redundant. These give ships better maneuverability than a fixed propeller and rudder system.
This glossary of nautical terms is an alphabetical listing of terms and expressions connected with ships, shipping, seamanship and navigation on water. Some remain current, while many date from the 17th to 19th centuries. The word nautical derives from the Latin nauticus, from Greek nautikos, from nautēs: "sailor", from naus: "ship".
A ship's wheel or boat's wheel is a device used aboard a water vessel to steer that vessel and control its course. Together with the rest of the steering mechanism, it forms part of the helm. It is connected to a mechanical, electric servo, or hydraulic system which alters the horizontal angle of the vessel's rudder relative to its hull. In some modern ships the wheel is replaced with a simple toggle that remotely controls an electro-mechanical or electro-hydraulic drive for the rudder, with a rudder position indicator presenting feedback to the helmsman.
Trim tabs are small surfaces connected to the trailing edge of a larger control surface on a boat or aircraft, used to control the trim of the controls, i.e. to counteract hydro- or aerodynamic forces and stabilise the boat or aircraft in a particular desired attitude without the need for the operator to constantly apply a control force. This is done by adjusting the angle of the tab relative to the larger surface.
A servo tab is a small hinged device installed on an aircraft control surface to assist the movement of the control surfaces. Introduced by the German firm Flettner, servo tabs were formerly known as Flettner tabs. Servo tabs are not true servomechanisms, as they do not employ negative feedback to keep the control surfaces in a desired position; they only provide a mechanical advantage to the pilot.
A vertical stabilizer or tail fin is the static part of the vertical tail of an aircraft. The term is commonly applied to the assembly of both this fixed surface and one or more movable rudders hinged to it. Their role is to provide control, stability and trim in yaw. It is part of the aircraft empennage, specifically of its stabilizers.
The Learjet 25 is an American ten-seat, twin-engine, high-speed business jet aircraft manufactured by Learjet. It is a stretched version of the Learjet 24.
Model yachting is the pastime of building and racing model yachts. It has always been customary for ship-builders to make a miniature model of the vessel under construction, which is in every respect a copy of the original on a small scale, whether steamship or sailing ship. There are fine collections to be seen at both general interest museums such as the Victoria and Albert Museum in London and at many specialized maritime museums worldwide. Many of these models are of exquisite workmanship, every rope, pulley or portion of the engine being faithfully reproduced. In the case of sailing yachts, these models were often pitted against each other on small bodies of water, and hence arose the modern pastime. It was soon seen that elaborate fittings and complicated rigging were a detriment to rapid handling, and that, on account of the comparatively stronger winds in which models were sailed, they needed a greater draught. For these reasons modern model yachts, which usually have fin keels, are of about 15% or 20% deeper draught than full-sized vessels, while rigging and fittings have been reduced to absolute simplicity. This applies to models built for racing and not to elaborate copies of steamers and ships, made only for show or for " toy cruising."
A radio-controlled boat is a boat or ship model controlled remotely with radio control equipment.
Weather helm is the tendency of sailing vessels to turn towards the source of wind, creating an unbalanced helm that requires pulling the tiller to windward in order to counteract the effect.
Wind-powered vehicles derive their power from sails, kites or rotors and ride on wheels—which may be linked to a wind-powered rotor—or runners. Whether powered by sail, kite or rotor, these vehicles share a common trait: As the vehicle increases in speed, the advancing airfoil encounters an increasing apparent wind at an angle of attack that is increasingly smaller. At the same time, such vehicles are subject to relatively low forward resistance, compared with traditional sailing craft. As a result, such vehicles are often capable of speeds exceeding that of the wind.
The Bluejacket 23 is a 23-foot (7.0 m) Canadian trailerable, fibreglass monohull sailboat designed by Cuthbertson & Cassian as a day sailer and club racer and first built in 1967.
This glossary of nautical terms is an alphabetical listing of terms and expressions connected with ships, shipping, seamanship and navigation on water. Some remain current, while many date from the 17th to 19th centuries. The word nautical derives from the Latin nauticus, from Greek nautikos, from nautēs: "sailor", from naus: "ship".