How to Raise the Mainsail

Man looking up at sailboat sails

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Raising the mainsail is one of the first steps in setting sail. Although usually a simple, easy process, beginners may experience snags if they’re not careful. Follow these guidelines to get the main up smoothly and the boat underway.

The mainsail is raised up the mast by the main halyard, a rope or wireline that rises from deck level to the masthead, through a block, and down to a shackle that connects to the top corner of the mainsail, the head. The halyard may also rise up through the mast to reduce windage aloft, as in the boat shown in this photo, and exit at a point near the deck. Pulling down on the halyard raises the sail. In most cases, the mainsail is raised and the boat is underway before the jib is raised or unfurled.

Steps to Raising the Mainsail

  1. On a small sailboat on a dock or mooring, the mainsail is typically raised before the boat is underway, following these steps:
  2. Attach the shackle to the clew in the head of the mainsail. Use pliers or a shackle knife to ensure it is tight, or vibration could release the shackle while sailing.
  3. Release or loosen the mainsheet so that wind against the rising sail does not cause resistance. The goal is for the leading edge of the sail to face into the wind so that the sail is not strained by wind blowing against either side.
  4. Ensure the sail is ready to be hoisted, with the boltrope or sail slugs at the sail's luff in the sail groove of the mast.
  5. Pull the halyard down by hand until the luff is tight. If the halyard becomes tight before the sail is up, check that the bolt rope or sail slugs are not jamming, and look aloft to ensure the free section of the main halyard has not wrapped around something. If there is a jam, lower the sail a bit to clear it, then proceed.
  6. When the luff is as tight as you can get it, cleat off the halyard.
  7. Now you’re ready to go. Sheet in the main to get the boat moving forward, or back the main (manually push the boom out into the wind) to turn the boat off the wind to begin sailing.

Raising the Mainsail on Large Boats

On a larger sailboat with a bigger mainsail, the process is similar but usually involves additional steps:

  1. Because the bow must point directly or nearly into the wind to ease tension on the mainsail as it rises, the sailboat usually motors off the dock and into the wind in preparation for raising the main. At anchor or on a mooring, unless there is a strong counter-current, the bow will naturally face into the wind.
  2. After ensuring the shackle is tight and the halyard clear to run up, loosen the mainsheet slightly while the boat maintains its orientation into the wind. Then start raising the main by hand.
  3. On a larger boat, a winch is usually needed at some point because of the weight of the mainsail. The winch may be located on the mast, a straight pull down on the halyard from the masthead, or in the cockpit, where the halyard is led through one or more turning blocks. Wrap the halyard on the winch and start cranking to continue hoisting the main until the luff is tight.
  4. As with a smaller boat, keep watching that the sail is moving up smoothly and does not jam. Because of the winch’s power, if you keep cranking in the halyard when the sail or halyard jams, you may break something!
  5. When the luff is tight, cleat off the halyard. Bring in the main with the mainsheet to start the boat underway.

Problems to Watch For

  • Loose shackle: Many sailors remove the mainsail shackle after each sail and affix it elsewhere such as to the lifeline; then they tighten it each time. Sailors who leave the halyard attached to the sail for extended periods, however, should check occasionally to ensure it hasn’t loosened up.
  • Jammed sail slugs: Sail slugs wear and may jam in the sail slot, or the slot may become dirty and cause jamming. If the sail is getting harder to raise, check the slugs to see if they need replacing and lubricate the sail track.
  • Snagged halyard: A halyard that is too loose may flop around and snag on any mast fitting, such as an attachment for lazy jacks, or may even wrap around a spreader.
  • Frayed halyard: A seriously frayed halyard may jam in the block at the masthead. Although the sail can usually still be moved up and down, inspect the length of the halyard to see if it has frayed or worn at any point. If so, replace it before it breaks.
  • Broken halyard block: If the halyard is running free but seems to jam at the masthead, you may need to climb the mast to inspect the block. Its sheave could be cracked or damaged. In such case have it repaired right away. It can be dangerous not to be able to drop the mainsail immediately if the wind comes up suddenly.