In boating, a fender is a bumper used to absorb the kinetic energy of a berthing boat

Boat

A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...

 or vessel against a jetty, quay wall or other vessel. Fenders are used to prevent damage to boats, vessels and berthing structures. Fenders are nowadays constructed in several ways, typically of rubber, foam elastomer or plastic. Rubber fenders are either extruded or made in a mould. Which type of fender is most suitable for an application depends on a lot of variables, including dimensions and displacement of the vessel, maximum allowable stand-off, berthing structure, tidal variations and other berth specific conditions.

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

Boats usually have mobile fenders which are placed between the boat and the dock as the boat approaches the dock. Docks and other bodies to which boats may approach, such as canal entrances and bases of bridges, have permanent fenders placed to avoid damage from boats. Old tires are often reused as fenders in such places.

Ship to quay (STQ)

Marine fenders are used at ports and docks on quay walls and other berthing structures. They are used to absorb the kinetic energy of a berthing vessel and thus prevent damage to the vessel or the berthing structure. There are many types of marine fenders such as

• Cylindrical fenders
• Arch fenders
• Cell fenders
• Cone fenders
• Pneumatic fenders
• foam elastomer fenders

Ship-to-ship (STS)

For bunkering operations between two vessels, typically floating fenders like pneumatic or foam elastomer fenders are used.

Boat

Boat fenders are used on the ship. Boat fenders required for small boats, tug boats, small ferries, naval speed boats and vessels, passenger vessels, luxury yachts, fishing boats, etc. Boat fenders also available in different types such as

• D fenders
• Square fenders
• Wing fenders
• Keyhole fenders
• Tug boat fenders
• Lightweight foam elastomer fenders

Applications and function

• Cylindrical fenders

Cylindrical fenders are commonly used fenders recommended for all types of application to ensure a safe and linear berthing for the different kind of vessels. Cylindrical (extruded) fenders are an economical solution to protect most of the berthing structures and offer much ease for installation.

• Arch fenders

Arch fenders were introduced to improve upon the performance of Cylindrical fenders. Arch fenders are having a better Energy / Reaction force ratio and recommended for all types of applications. The very shape of these fenders helps to dissipate the stresses evenly. These extruded fenders are very easy to install and are maintenance free. Generally preferred for small to medium range Vessels.

• Cell fenders

Cell fenders are best employed for smallest to biggest Vessels where Reaction Force is an important criteria. Among all types of fenders, Cell fenders offer minimum reaction per ton-meter energy absorbed. The very geometrical shape gives it sturdiness, shear resistance, compact Structure and the capacity to absorb energy equally from all directions. The Cylindrical buckling column absorbs axial loads effectively and buckles radially. This results in multi directional dispersion of energy. Cell fenders are the most durable rubber fenders available and are currently the largest moulded fenders made. 2000-2500 mm high cell fenders are typically used for LNG berths. In order to distribute the reaction force, cell fenders are typically supplied with large fender panels, which keeps the hull pressure low.

• Cone fenders

Cone fenders are an improved version of Cell type Fender recently introduced and recommended for all type of applications including high tidal variation sites. This advanced feature of lesser height of fenders improves material handling capabilities of Deck / Vessel Cranes which reduces overall cost of the project. Due to the geometrical shape of the fenders it can deflect more and it can absorb more energy from any direction. Maintaining reaction force, but doubling energy absorption, can be achieved by using two identical cone fenders in a back-to-back arrangement. In order to distribute the reaction force, cone fenders are typically supplied with large fender panels, which keeps the hull pressure low.

• Pneumatic fenders

These fenders are extensively used for ship to ship transfers at mid seas, double banking operation as well as vessel to berth at dock/jetties. The Special property of Pneumatic fender is its low reaction force at low Deflection. This very property of pneumatic fenders makes them most suitable fender for liquid cargo vessels and defence vessels with very sensitive equipments.These fenders offer excellent energy absorption characteristic and do have a linear Load Deflection Characteristic. Pneumatic fenders should comply to the ISO 17357 standard.

• Foam elastomer fenders

These fenders are typically made of a closed-cell Polyethylene foam core, which is encapsulated in a nylon or Kevlar reinforced Polyurethane skin. The performance of foam elastomer fenders is comparable to that of a pneumatic fender, but the fenders will not lose their function in case the skin gets punctured. Foam elastomer fenders cannot deflate.

• D fenders

D type fenders are commonly used on vessels as well as small jetties. They are compression moulded with steel inserts if required.

• Square fenders

Square fenders are commonly used on vessels as well as small jetties. They are compression moulded fenders generally used on tugs, boats and ships.

• Wing fenders

Wing fenders are compression moulded fenders and are generally used on tugs, boats and ships. Easy to install and replace. Do have excellent sea water resistance and resistance to ozone ageing and ultra violet rays.

• Keyhole fenders

Keyhole fenders are the most versatile bow, stem fenders used on the Tugs Boats and small Port Crafts/Ferries. They offer maximum protection to the Tugs/Ferries with its typical profile and load absorbing capabilities.

• Tug boat fenders

These fenders are made of high abrasion resistance rubber with good resilience properties for required application. They are very popular with small port craft owners and tug owners. These fenders are compression moulded in high pressure thermic fluid heated moulds and do have excellent sea water resistance.

Fender design

There are a number of different standards used worldwide to design fender systems. The most commonly used one, is the PIANC "Guidelines for the design of fender systems, 2002" , which is the update of its predessecor from 1984. In Japan the Japanese Industrial Standards (JIS) are commonly used, where as in the United Kingdom and the United States of America, the British Standard BS 6349:part 4 still used quite regularly..

Designing a fender system basically is determining what the berthing energy of a vessel or range of vessels will be, then determine what capacity the fender needs to have to absorb that kinetic energy and finally how to find a way to avoid the reaction force creating too much hull pressure. In principle, a berthing energy calculation is a simple kinetic energy calculation, adjusted for specific behaviour of a berthing vessel or the specific characteristics of the berthing location or structure.