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A chopper is a propeller design largely of interest for production outboards on fast pad v-bottom boats. Unlike a cleaver the chopper's trailing edge extends aft with a large chord line at each radius. Choppers provide good acceleration and top speed and generally have relatively high rake, which has the effect of increasing the boat's angle of attack without changing the motor trim. This trimming effect is mistakenly called 'bow lift'.
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A propeller is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a boat through water or an aircraft through air. The blades are shaped so that their rotational motion through the fluid causes a pressure difference between the two surfaces of the blade by Bernoulli's principle which exerts force on the fluid. Most marine propellers are screw propellers with helical blades rotating on a propeller shaft with an approximately horizontal axis.
A vehicle is a machine designed for self-propulsion, usually to transport people, cargo, or both. The term "vehicle" typically refers to land vehicles such as human-powered vehicles, animal-powered transports, motor vehicles and railed vehicles, but more broadly also includes cable transport, watercraft, amphibious vehicles, aircraft and space vehicles.
An outboard motor is a propulsion system for boats, consisting of a self-contained unit that includes engine, gearbox and propeller or jet drive, designed to be affixed to the outside of the transom. They are the most common motorised method of propelling small watercraft. As well as providing propulsion, outboards provide steering control, as they are designed to pivot over their mountings and thus control the direction of thrust. The skeg also acts as a rudder when the engine is not running. Unlike inboard motors, outboard motors can be easily removed for storage or repairs.
Seamanship is the art, competence, and knowledge of operating a ship, boat or other craft on water. The Oxford Dictionary states that seamanship is "The skill, techniques, or practice of handling a ship or boat at sea."
A jetboat is a boat propelled by a jet of water ejected from the back of the craft. Unlike a powerboat or motorboat that uses an external propeller in the water below or behind the boat, a jetboat draws the water from under the boat through an intake and into a pump-jet inside the boat, before expelling it through a nozzle at the stern.
A skeg is a sternward extension of the keel of boats and ships which have a rudder mounted on the centre line. The term also applies to the lowest point on an outboard motor or the outdrive of an inboard/outboard. In more recent years, the name has been used for a fin on a surfboard which improves directional stability and to a movable fin on a kayak which adjusts the boat's centre of lateral resistance. The term is also often used for the fin on water skis in the U.S. It has been used for the vertical fin on seaplane hulls and floats. The wear-bar on the bottom of snowmobile ski may also be called a skeg.
USS Chopper (SS/AGSS/IXSS-342) was a Balao-class submarine of the United States Navy. It was their only ship to be named for the chopper, a common name for Pomatomus saltatrix, an aggressive game fish. She was in commission from 1945 to 1969, her active career ending due to damage from a nearly fatal accident.
A motorboat or powerboat is a boat that is exclusively powered by an engine; faster examples may be called "speedboats".
In aeronautical and naval engineering, pusher configuration is the term used to describe a drivetrain of air- or watercraft with propulsion device(s) after the engine(s). This is in contrast to the more conventional tractor configuration, which places them in front.
Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque. Examples include some aircraft propellers, resulting in the maximum power of a single piston or turboprop engine to drive two propellers in opposite rotation. Contra-rotating propellers are also common in some marine transmission systems, in particular for large speed boats with planing hulls. Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission. The configuration can also be used in helicopter designs termed coaxial rotors, where similar issues and principles of torque apply.
Aircraft equipped with contra-rotating propellers (CRP) coaxial contra-rotating propellers, or high-speed propellers, apply the maximum power of usually a single piston engine or turboprop engine to drive a pair of coaxial propellers in contra-rotation. Two propellers are arranged one behind the other, and power is transferred from the engine via a planetary gear or spur gear transmission. Contra-rotating propellers are also known as counter-rotating propellers, although the term counter-rotating propellers is much more widely used when referring to airscrews on separate non-coaxial shafts turning in opposite directions.
An airboat is a flat-bottomed watercraft propelled by an aircraft-type propeller and powered by either an aircraft or automotive engine. It is commonly used for fishing, hunting, recreation, and ecotourism.
Ballast is weight placed low in ships to lower their centre of gravity, which increases stability. Insufficiently ballasted boats tend to tip or heel excessively in high winds. Too much heel may result in the vessel filling with water and/or capsizing. If a sailing vessel needs to voyage without cargo, then ballast of little or no value will be loaded to keep the vessel upright. Some or all of this ballast will then be discarded when cargo is loaded.
Propeller walk is the term for a propeller's tendency to rotate about a vertical axis. The rotation is in addition to the forward or backward acceleration.
Manoeuvering thrusters are transversal propulsion devices built into or mounted to either the bow or stern of a ship or boat to make it more manoeuvrable. Bow thrusters make docking easier, since they allow the captain to turn the vessel to port or starboard side, without using the main propulsion mechanism which requires some forward motion for turning; The effectiveness of a thruster is curtailed by any forward motion due to the Coandă effect. A stern thruster is of the same principle, fitted at the stern. Sufficiently large vessels often have multiple bow thrusters and stern thrusters.
SS Tahoe was a steamship that operated on Lake Tahoe at the end of the 19th century and the first half of the 20th. Scuttled in 1940, the wreck presently lies in 400 feet (120 m) of water off Glenbrook, Nevada. The wreck was first visited in 2002 by a team from New Millennium Dive Expeditions (NMDE) in a record-setting high-altitude dive for Lake Tahoe. As a result of the work that NMDE did on the Tahoe site from 1999 up to their dives in 2002, Tahoe became the first maritime site in Nevada to be listed in the National Register of Historic Places.
The draft or draught of a ship is a determined depth of the vessel below the waterline, measured vertically to its hull's lowest—its propellers, or keel, or other reference point. Draft varies according to the loaded condition of the ship. A deeper draft means the ship will have greater vertical depth below the waterline. Draft is used in under keel clearance calculations, where the draft is calculated with the available depth of water to ensure the ship can navigate safely, without grounding. Navigators can determine their draught by calculation or by visual observation.
A ducted propeller, also known as a Kort nozzle, is a marine propeller fitted with a non-rotating nozzle. It is used to improve the efficiency of the propeller and is especially used on heavily loaded propellers or propellers with limited diameter. It was developed first by Luigi Stipa (1931) and later by Ludwig Kort (1934). The Kort nozzle is a shrouded propeller assembly for marine propulsion. The cross-section of the shroud has the form of a foil, and the shroud can offer hydrodynamic advantages over bare propellers, under certain conditions.
The RFB X-113 Aerofoil Boat was an experimental ground effect vehicle intended to work over water. It was one of three such aircraft designed by Alexander Lippisch in the 1960s and early 1970s. The X-113 first flew in 1970; only one was built.
Clifford A. "Sonny" Vaughs was an American civil rights activist, filmmaker, and motorcycle builder. Vaughs designed the two chopper motorcycles used for the 1969 film Easy Rider, while an associate producer on the film. He also produced and directed the documentary What Will the Harvest Be? (1965) and Not So Easy (1972).