Parts of a Boat

A defined degree of capability or reliability required from equipment, a system or a person. The applicable standard specifies how the level is measured and the conditions under which it applies. The phrase is context-dependent and should be accompanied by the governing rule, specification or training scheme.

A spring-loaded metal hank used to attach a sail’s luff to a stay. Retracting the piston opens the hook for fitting or removal, while the spring locks it closed in use. Hanks should run freely, face consistently and be checked for wear, corrosion and sharp edges that could damage sail or stay.

A sail whose foot is attached at the tack and clew but not continuously secured to the boom. The arrangement permits direct control of foot depth with the outhaul and allows the lower sail to assume a smooth shape. Loads remain concentrated at the reinforced corner fittings and their attachments.

The ratio by which a machine multiplies an applied force. In an ideal tackle it relates to the number of rope parts supporting the moving load, while friction reduces the advantage available in practice. Greater purchase requires more rope movement and does not reduce the load carried by every component equally.

The horizontal foretriangle measurement from the front of the mast at deck level to the forestay intersection with the deck or bowsprit datum. It is used with the I measurement to describe rig proportions and in sail-rating or design calculations. The exact measurement points follow the applicable rating rule or designer’s convention.

A mast that passes through the deck and bears on a structural step at or near the keel. Compression is carried directly into the lower structure, while partners at deck level provide support and sealing. Water ingress, corrosion, step condition and alignment at the partners require inspection.

A material made by bonding two or more layers to combine their properties. Marine laminates include fibre-reinforced hull structures and sailcloth films with load-bearing fibres. Performance depends on fibre direction, resin or adhesive, consolidation and protection from moisture, heat, ultraviolet exposure and repeated flexing.

The tension along the after edge of a sail. It influences twist, flutter and the sail’s ability to maintain an efficient exit shape. Sheets, vang, traveller, halyard and leech line can affect it, but excessive tension may hook the leech and increase drag.

A mainsail reefing and stowage system in which the sail rolls around a foil inside the mast. The sail is deployed and reduced using furling and outhaul controls while maintaining suitable tension and boom angle. Poor sail shape, damaged battens, loose cloth or incorrect handling can cause a jam that is difficult to resolve under…

The accidental winding of a halyard around a stay, mast fitting or furling sail. It can jam a furler and, under high load, damage the stay or rig. Correct halyard lead, adequate separation and suitable restrainers reduce the risk; a jam should not be forced without identifying the wrap.