spring

In shipyard and marine work, to spring a vessel means to rotate it around a fixed point, typically using a rope (the spring) attached to the anchor cable or a fixed bollard ashore. The spring provides a mechanical advantage that allows a large ship to pivot in place without engine power, relying instead on tugboat assistance, winches, or current. This is essential in tight berths where a ship cannot maneuver freely or where engine use risks collision or damage.

The technique works because the spring rope is rigged from a point on the vessel's hull (often amidships on one side) back to an anchor or shore fixture. As the rope is tensioned and heaved, the hull pivots around the anchor point. The heavier the vessel and the more constrained the space, the more critical spring work becomes. In crowded shipyards or when moving between tightly spaced piers, springing can shift a vessel a few degrees to align it properly for departure or to position it for work.

A forward spring runs from the ship's bow area aft to the anchor or bollard, rotating the stern away. An after spring runs from the stern forward, rotating the bow away. Both may be used together to hold position or to rotate methodically. The spring rope itself is typically a heavy natural fiber line or steel wire rope, sized for the tonnage and strength required. Smaller vessels might use a single spring; larger ships routinely deploy two or more in combination with slack mooring lines.

Common problems include uneven tension causing jerking motions that stress hull fittings, fouling of the spring rope on propellers or appendages, and miscalculation of the pivot point, which can swing the vessel into an adjacent ship or structure. The operation requires careful coordination between the vessel's crew, tugboat operators if assisting, and shore crews managing winches or holding the anchor.

The term likely derives from the elastic or springlike action of the rope under tension, and the way the ship appears to spring or rotate around its fixed point. Springing is distinct from warping, which uses multiple lines to move a vessel forward or sideways, and from kedging, which involves hauling on an anchor placed some distance away. In modern practice, some yards have replaced springing with bow thrusters or azimuth thrusters on larger vessels, but the technique remains standard for conventional ships and in facilities where thruster equipment is not available.