Motorized craft
 | This section is empty. You can help by adding to it. (September 2023) |
There are two different meanings to the term lee helm depending on whether one is discussing sailboats or motorized ships.
Lee helm is the tendency of a sailboat to turn away from the wind while under sail. It is the opposite of weather helm (the tendency of a sailboat to "round up" into the wind). A boat with lee helm will be difficult to sail close hauled, and tacking may be difficult.
Lee helm is considered dangerous in a sailboat. While sailing, an undirected boat with lee helm will bear (turn) away from the wind, accelerate, and perform an accidental or uncontrolled gybe, perhaps repeatedly. In an uncontrolled gybe, the force of the wind moves the sails and boom from one side of the boat to the other. In a strong wind, this movement will be very fast and forceful... and can damage the boat, the sails, injure the crew, or cause the boat to broach (lay over on its side).
The cause of lee helm is that the center of pressure exerted by the wind on the sails falls too far forward of the center of resistance of the hull — the natural point at which the hull tries to pivot. This tends to push the bow of the boat away from the wind. This can be due to a poor design, for example with the mast too far forward.
A small amount of lee helm can be counter-acted with the rudder, but this introduces significant drag in the water and slows the boat. A small amount of lee helm can also be cured by raking the mast backward (which moves the center of pressure aft), reducing the size of the jib on a sloop rigged boat, or increasing the size of the mizzen sail on a yawl or a ketch. Large amounts of lee helm can only be corrected by altering the placement of the mast(s) or keel/centerboard --- a non-trivial venture.
Ideally, a sailboat's sail plan should allow for a neutral helm, avoiding Weather Helm's tendency to round up too strongly (and perhaps place the boat 'in irons') or Lee Helm's tendency to make the boat fall off from the wind, possibly in an uncontrolled and dangerous jibe. How this balance is achieved will differ from sail plan to sail plan, depending on where the sails are carried relative to the center of effort of the hull. [1] [2]
| | This section is empty. You can help by adding to it. (September 2023) |
Traditionally, two stations are on the bridge of a ship for controlling the vessel's maneuvers: the helm, which uses a wheel (or touchscreen equivalent) to send signals to control the position of the rudder or rudders, and the lee helm, which traditionally inputs speed commands by operating an engine order telegraph to send engine commands to the engineering personnel below decks. On modern US Navy surface vessels using gas turbine or diesel propulsion, the lee helm directly controls the ship's speed via throttle (either a manual throttle lever or a touch screen on some ships). The bridge throttle directly manipulates propeller pitch and/or engine RPM any time the bridge station is in control, or switches to a traditional order telegraph during those rare situations the bridge station relinquishes control or if the control system fails. The lee helm on vessels with nuclear propulsion (carriers and submarines) and conventional steam propulsion (amphibious assault ships prior to LHD-8) uses a telegraph. One origin for the lee helm designation for the engine order-telegraph—large sailing ships had a helmsman at the wheel, plus an auxiliary helmsman positioned on the leeward side of the helm – hence the term lee helm – to assist the helmsman in controlling the wheel while coming about or while the vessel is laboring in high winds or an extreme sea state. [3]
The US Navy's Integrated Bridge and Navigation System (IBNS) uses two touchscreens and steering wheel for steering. The helm is on the left, and the lee helm is on the right. In August 2017, the destroyer USS John S. McCain was involved in a collision resulting in massive casualties, including the deaths of ten American sailors. The NTSB accident report found an unreliable IBNS and lack of training were the causes of the accident. [4]
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 sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture.
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium. On an airplane, 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.
A jibe (US) or gybe (Britain) is a sailing maneuver whereby a sailing vessel reaching downwind turns its stern through the wind, which then exerts its force from the opposite side of the vessel. Because the mainsail boom can swing across the cockpit quickly, jibes are potentially dangerous to person and rigging compared to tacking. Therefore, accidental jibes are to be avoided while the proper technique must be applied so as to control the maneuver. For square-rigged ships, this maneuver is called wearing ship.
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.
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".
Proas are various types of multi-hull outrigger sailboats of the Austronesian peoples. The terms were used for native Austronesian ships in European records during the Colonial era indiscriminately, and thus can confusingly refer to the double-ended single-outrigger boats of Oceania, the double-outrigger boats of Island Southeast Asia, and sometimes ships with no outriggers or sails at all.
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.
A bridge, also known as a pilothouse or wheelhouse, is a room or platform of a ship from which the ship can be commanded. When a ship is under way, the bridge is manned by an officer of the watch aided usually by an able seaman acting as a lookout. During critical maneuvers the captain will be on the bridge, often supported by an officer of the watch, an able seaman on the wheel and sometimes a pilot, if required.
A helmsman or helm is a person who steers a ship, sailboat, submarine, other type of maritime vessel, or spacecraft. The rank and seniority of the helmsman may vary: on small vessels such as fishing vessels and yachts, the functions of the helmsman are combined with that of the skipper; on larger vessels, there is a separate officer of the watch who is responsible for the safe navigation of the ship and gives orders to the helmsman, who physically steers the ship in accordance with those orders.
In sailing, heaving to is a way of slowing a sailing vessel's forward progress, as well as fixing the helm and sail positions so that the vessel does not have to be steered. It is commonly used for a "break"; this may be to wait for the tide before proceeding, or to wait out a strong or contrary wind. For a solo or shorthanded sailor it can provide time to go below deck, to attend to issues elsewhere on the boat or to take a meal break. Heaving to can make reefing a lot easier, especially in traditional vessels with several sails. It is also used as a storm tactic.
Self-steering gear is equipment used on sail boats to maintain a chosen course or point of sail without constant human action.
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.
A sailing yacht, is a leisure craft that uses sails as its primary means of propulsion. A yacht may be a sail or power vessel used for pleasure, cruising, or racing. There is no standard definition, so the term applies here to sailing vessels that have a cabin with amenities that accommodate overnight use. To be termed a "yacht", as opposed to a "boat", such a vessel is likely to be at least 33 feet (10 m) in length and have been judged to have good aesthetic qualities. Sailboats that do not accommodate overnight use or are smaller than 30 feet (9.1 m) are not universally called yachts. Sailing yachts in excess of 130 feet (40 m) are generally considered to be superyachts.
The center of lateral resistance is the center of pressure of the hydrodynamic forces on the hull of a boat. The center of pressure is the point on a body where the total sum of a pressure field acts, causing a force and no moment about that point. The total force vector acting at the center of pressure is the value of the integrated vectorial pressure field. The resultant force and center of pressure location produce equivalent force and moment on the body as the original pressure field. Pressure fields occur in both static and dynamic fluid mechanics. Specification of the center of pressure, the reference point from which the center of pressure is referenced, and the associated force vector allows the moment generated about any point to be computed by a translation from the reference point to the desired new point.
The B&R 23 is a sailing boat designed in the early 1990s. It has an ultralight construction with a very large sail plane. Typical crew is a helmsman and two deck hands in trapezes. The boat is predominantly used for racing.
Dismasting, also spelled demasting, occurs to a sailing ship when one or more of the masts responsible for hoisting the sails that propel the vessel breaks. Dismasting usually occurs as the result of high winds during a storm acting upon masts, sails, rigging, and spars. Over compression of the mast owing to tightening the rigger too much and g-forces as a consequence of wave action and the boat swinging back and forth can also result in a dismasting. Dismasting does not necessarily impair the vessel's ability to stay afloat, but rather its ability to move under sail power. Frequently, the hull of the vessel remains intact, upright and seaworthy.
Kaep is a traditional type of double-ended Proa sailboat native to Palau. Some of the essential design elements have also been adopted as a modern smaller multihull prototype variant.
The Marlow-Hunter 37 is an American sailboat that was designed by Glenn Henderson as a cruiser and first built in 2014.
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".
This article incorporates public domain material from United States National Transportation Safety Board. Collision between US Navy Destroyer John S McCain and Tanker Alnic MC (PDF). National Transportation Safety Board . Retrieved December 21, 2019. (NTSB/MAR-19/01PB2019-100970).