fender

To fender means to deploy protective barriers between a vessel's hull and a fixed structure or another ship, absorbing impact energy during mooring, docking, or alongside operations. Fenders are pneumatic or foam-filled bumpers hung vertically along the gunwale or hull side; they compress on contact rather than letting wood, steel, or fiberglass make direct contact with pilings, quay walls, or neighboring vessels.

Fender deployment varies by vessel size and approach conditions. Small fishing boats may use rope-wrapped tires or simple cylindrical foam tubes. Commercial ships use manufactured rubber fenders, typically 18 to 36 inches in diameter, suspended by chains or steel cables at intervals matched to the hull profile. Mooring operations, where precise lateral positioning is critical, demand fenders at bow, stern, and at least two points amidships. Tugboat captains fender the bow and quarter before making contact with larger vessels.

Materials and performance

Pneumatic fenders (air-inflated rubber cylinders) can absorb greater total energy because they compress progressively; reaction force builds as internal pressure rises. Solid foam fenders (typically polyurethane or closed-cell foam core wrapped in rubber) compress to a fixed depth and offer simpler maintenance but less forgiveness for high-impact docking. Fender selection depends on berthing speed (usually 0.3 to 0.5 meters per second for controlled mooring) and the mass being stopped.

Failure modes are predictable. Over-inflation of pneumatic fenders reduces compression, transmitting shock directly to the hull and mooring hardware. Under-inflation or puncture makes the fender useless; a skipper must inspect air pressure before critical operations. Foam fenders degrade from UV exposure and oil contact, becoming brittle or slick. Improper rigging (too few fenders, gaps in coverage, or height misalignment) leaves the hull vulnerable to corner impacts or glancing blows that bypass protection.

The verb fender appears most often in mooring orders and casualty reports: 'fender the starboard side' means position bumpers before closing on the dock. In shipyard talk, fender off describes the act of pushing a vessel away from contact using the fenders as intermediaries, rather than risking a direct hull strike.