Outhaul

A line or tackle system used to adjust the tension and position of the sail’s clew along the boom, affecting the sail’s shape and performance.

The outhaul is an essential control line on a sailing vessel, particularly for adjusting the mainsail. It is attached to the clew of the sail, which is the lower aft corner, and runs along the boom. By tightening or loosening the outhaul, sailors can modify the sail’s foot tension, which in turn alters the sail’s shape and efficiency. When the outhaul is tightened, it pulls the clew aft, flattening the sail. This is particularly useful in stronger winds, as a flatter sail reduces drag and helps maintain control. Conversely, loosening the outhaul allows the sail to become fuller, which is advantageous in lighter winds because it increases the sail’s power by creating a more curved shape that can catch more wind.

The outhaul is often part of a more complex system of blocks and pulleys, especially on larger yachts, to provide mechanical advantage and make it easier to adjust under load. On smaller boats, it may simply be a line that can be manually adjusted. The proper use of the outhaul is critical for optimising sail trim and boat speed, and it is one of the primary sail controls used in conjunction with the mainsheet, vang, and traveller to manage the sail’s shape. Understanding how to use the outhaul effectively is a key skill for sailors, as it directly influences the boat’s performance across different wind conditions.