Points of Sail

The time, distance or speed lost while a sailing vessel changes from one tack to the other. The vessel turns through the no-go zone, sails travel and speed must be rebuilt. Sea state, crew work, foil efficiency and the amount of over- or under-steering determine the size of the loss.

The aerodynamic interaction between adjacent sails, especially a headsail and mainsail. The sails alter pressure and airflow around each other, affecting lift, separation and the useful operating angle of the combination. Effective slot width and shape depend on trim, overlap, twist and apparent wind rather than a simple nozzle action.

The horizontal angle at which a sheet pulls a sail relative to the vessel’s centreline or sail plane. It influences angle of attack, slot geometry and pointing ability. Lead position must also give suitable vertical pull so foot and leech tension remain balanced.

The event-specific rules and directions issued for a sailing race or regatta. They define matters such as course, signals, schedule, starting and finishing arrangements, penalties and local procedures and may change permitted racing-rule provisions. Competitors must read them with the notice of race and official amendments.

To sail with the wind well abaft the beam and the sheets eased. The sails are allowed to draw without being close-hauled, commonly on a broad reach or run. Course and trim must avoid an accidental gybe and excessive rolling or blanketing.

The angle between a vessel’s fore-and-aft line and the apparent wind direction. It is normally measured from the bow on the side from which the wind is felt. Boat speed and course alter apparent wind angle even when true wind is unchanged, making it a primary reference for steering and sail trim.

A headsail held or sheeted to windward so its aerodynamic force acts opposite to its usual direction. It is used during heaving-to, some tacking techniques and manoeuvres requiring the bow to be pushed away from the wind. Loads and sheet leads must be controlled because the sail can fill suddenly.

The route and attachment position through which a sheet pulls on a sail. Moving the lead changes the balance of tension between a sail’s foot and leech and therefore alters twist and shape. A fair, correctly aligned lead also reduces chafe and side loading on blocks or fairleads.