sling

A sling is a metal band or rope loop that fastens a yard (the horizontal spar holding a sail) to the mast, allowing it to hang securely while still rotating to adjust sail angle. In traditional sailing ships, the sling bears most of the yard's weight and must support the dynamic forces created by wind pressure, the yard's own mass, and the weight of the canvas and rigging attached to it. The sling is positioned near the center of the yard, where stress is greatest.

Slings come in two main forms: iron bands, typically flat bar stock 50 to 75 mm wide depending on yard size, or rope slings made from hemp or modern synthetic fiber. Iron slings are standard on larger vessels and commercial ships because they resist abrasion, require minimal maintenance, and provide predictable strength. Rope slings appear on smaller craft and traditional vessels, where they are lighter and easier to replace when wear becomes visible. Many ships carry spare slings as wear items for routine replacement during overhaul.

The sling works in conjunction with the parrel, a smaller band or rope that sits just above it and prevents the yard from sliding up and down the mast. Together they position the yard at the correct height while allowing it to swing in the horizontal plane as the ship turns or the sails are trimmed. Without the sling, the yard would hang from the parrel alone, concentrating all stress on a single point and creating dangerous flexing in the mast.

Failure modes include metal fatigue and cracking at stress points, especially where the sling wraps around the mast and where it is bolted or welded. Rope slings fail through chafe, UV degradation, and loss of tensile strength over years of weathering and sunlight exposure. Inspection focuses on checking for cracks in iron slings using visual methods or magnetic particle testing, and on examining rope for discoloration, stiffness, and fraying that signal loss of fiber strength.

The term comes from its function: it slings, or suspends, the yard in place. The word appears in European maritime language by the 16th century and remains standard in shipbuilding, ship maintenance, and historical ship reconstruction. Related terms include parrel, truss (an assembly of sling and parrel), and jackstay (which runs along the yard itself rather than suspending it).