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Boat fender


In boating, a fender is a bumper used to absorb the kinetic energy of a boat or vessel berthing against a jetty, quay wall or other vessel. Fenders, used on all types of vessels, from cargo ships to cruise ships, ferries and personal yachts, prevent damage to vessels and berthing structures. To do this, fenders have high energy absorption and low reaction force. Fenders are typically manufactured out of rubber, foam elastomer or plastic. Rubber fenders are either extruded or made in a mold. The type of fender that is most suitable for an application depends on many variables, including dimensions and displacement of the vessel, maximum allowable stand-off, berthing structure, tidal variations and other berth-specific conditions. The size of the fender unit is based on the berthing energy of the vessel which is related to the square of the berthing velocity.

Historically, fenders were woven from rope in a variety of patterns. Fenders of woven rope are still used today by historic boat owners.

Yachts, small leisure craft and support vessels typically have mobile fenders which are placed between the boat and the dock as the boat approaches the dock. Docks and other marine structures, such as canal entrances and bases of bridges, have permanent fenders placed to avoid damage from boats. Old tires are often used as fenders in such places.

Fendering is also used on ports and berths as well. The fendering systems act as elastic buffer devices that are used to slow ships down and prevent damage to the ship or dock structure in the mooring process.

Marine fenders are used at ports and docks on quay walls and other berthing structures. They absorb the kinetic energy of a berthing vessel and thus prevent damage to the vessel or the berthing structure. There are 2 major categories of fenders for port applications: Fixed and Floating. Fixed fenders are mounted to the berth structure and compose of buckling fenders such as cell fenders, V-type fenders, and non-buckling fenders such as cylindrical fenders. Floating fenders are placed between the berth structure and ship, and include pneumatic fenders and foam-filled fenders.

Fender spacing should be determined by the smallest ship using the berth, as well as the design ships' hull radius of curvature. To ensure all ships can be accommodated at the berth, fender spacing should be about 5%-10% of the ship's length for vessels up to 20,000 dwt. Berths handling larger ships can should have a fender spacing of about 25%-50% of the ship's length.


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