How to Use a Sailboat's Outhaul

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The Outhaul Attaches to the Sail’s Clew

outhaul mainsail clew
Photo © Tom Lochhaas.

The outhaul on a sailboat is one of the controls, part of the boat’s running rigging. The outhaul is a line that connects to the clew of the mainsail (the ring in the lower aft corner) and pulls the sail back toward the end of the boom. On most boats, this line or wire cable passes around a block (pulley) down into the boom, as shown in this photo.

Below shows how the other end of the outhaul is pulled to tighten the tension in the sail’s foot and explains how to use the outhaul to your advantage in different sailing conditions.

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Adjust the Outhaul for Sailing Conditions

outhaul line at winch
Photo © Tom Lochhaas.

Shown here is the outhaul line exiting the boom (on the left), wrapped around a winch, and tied off on the cleat on the right. (The end of the boom is out of the picture to the left.) A winch is needed on moderate to large sailboats to exert enough tension on the foot of a large mainsail. The tighter the outhaul is pulled, the flatter the bottom of the sail becomes. The looser the outhaul, the fuller the sail.

How to Adjust the Outhaul

The principle for adjusting the outhaul is similar to that of using a boom vang in light and moderate wind.

  • In light wind, the outhaul should be fairly loose, allowing the mainsail to be fuller. Wrinkles may form along the foot of the sail.
  • In moderate wind, the outhaul should be moderately tight, flattening the sail and giving better shape for sailing upwind or on a reach.
  • In a stronger wind, when you might need to depower the main to prevent excessive heeling, the outhaul should be very tight. A flatter sail produces less heeling force.