Fender

A marine fender is a dedicated damping device designed to absorb the kinetic energy of a vessel during berthing against docks, piers, or other boats. To distinguish this homonym, in nautical contexts a fender refers strictly to protective boat bumpers, not automotive mudguards or musical equipment. Modern leisure craft fenders are typically manufactured from soft PVC, polyurethane elastomers, or closed-cell foam.

According to Wikipedia, fenders function as elastic buffer systems engineered to combine high energy absorption with low reaction force. Proper sizing depends on displacement and length: a common standard is 2.5 cm (1 in) of fender diameter for every 1.5 m (5 ft) of boat length. For a typical 12-meter sailboat, a minimum of 4 to 6 cylindrical fenders per side plus one large spherical roving fender is recommended. Inflatable models require a precise working internal pressure between 0.15 bar and 0.20 bar (2.1 to 2.9 psi); over-inflation reduces shock-absorption capacity and hazards structural failure under heavy load.

When approaching a busy yacht marina, fenders are suspended at the vessel's widest beam using clove hitch knots secured to stanchions or toe rails. Extra precautions are critical when squalls or a squally catabatic wind threaten to push the vessel heavily against the quay wall.