A chainplate is a steel plate anchored to the hull of a sailboat and connected to various parts of the rigging. Depending on the specific location and purpose of each chainplate, it may serve to help distribute weight, provide support, or serve as part of tension adjustment systems using turnbuckles attached to the chainplate and rigging cordage. Most chainplates are attached to shrouds or stays for the standard rigging, meaning these straps, or in some cases bars, are attached to turnbuckles to allow for the adjustment of tension on various cordage and sails used in most sailboats.
All sailboats, regardless of size or design, rely on rigging. Rigging is all the apparatus required to power the boat via wind, and includes masts, ropes, pulleys, sails, turnbuckles, and chainplates. Masts, the large wooden poles or beams seen on sailboats, provide the basic framing for sails. To control sails, thereby controlling speed and direction, sailors use a complex system of ropes and pulleys to open, close, and turn sails at various points on the masts. Such systems place pressure on rigging components and boat framing, requiring counter tension and load displacement via turnbuckles and chainplates.
Chainplates provide the ability to distribute the strain of counter tension across the structure of a sailboat. For example, chainplates anchor shrouds, the large net-like rigging used to keep masts upright. Deck-mount chainplates and stemhead fittings attach shroud cordage and other rigging apparatus to the boat at different places, depending on the support distribution needs of the boat. If wind properties change, stays and shrouds attached to the deck keep masts from swaying too far and snapping or capsizing the boat. Where such shrouds, stays, and associated chainplates are mounted depends on the specific needs of the boat.
Numerous chainplates are incorporated into a sailboat's rigging, with each chainplate having its own configuration, shape, material construction, and design elements relative to its placement and intended use. Some chainplates resemble steel bars with large bolts, while others resemble thin L-shaped brackets with screws, like those used in bookshelves. Steel is the most common material used in chainplates, although iron and other metals are not uncommon, especially in historic sailboat design plans. Several holes in the body of a chainplate allow displacement among several bolts where the chainplate is attached to the hull.
By using chainplates and other apparatus of rigging, sailboats with lighter hulls are better able to support complex rigging systems and components. The weight of shrouds and other stays on a sailboat are spread across the hull, along the deck, and against framing components through the use of chainplates and turnbuckles. Experienced sailors can quickly adjust to allow for changes in wind speed or direction, simply by screwing or unscrewing a turnbuckle attached to a chainplate.