Sailing With Lazy Jacks and Stack Packs | Modern Sailing

Sailing With Lazy Jacks and Stack Packs

What are lazy jacks and stack packs? 

Lazy jacks are networks of lines that are rigged along each side of the mainsail from multiple points on the boom or a stack pack to a point on the mast just above the spreaders, at about 60% the mast's height. Their purpose is to hold the mainsail on top of the boom when it is lowered.

Typically, lines called "legs" are joined with single lines called "risers" to form two upside-down Y shapes. However, lazy jack legs and risers can be rigged in a variety of configurations. Also, the legs can be joined to the risers with blocks, rings, or even tied together. The space between the two sets of lazy jacks on either side of the sail is known as the "pocket."

The stack pack (sometimes called a lazy pack or lazy bag) is a modern type of a sail cover. It is secured to the boom and zips closed at the top to protect the sail from sun damage when it's not in use.

Lazy jacks can be set up with or without a stack pack. When a stack pack is present, the lazy jacks are tied to the stack pack to support it. With no stack pack, the lazy jacks are rigged directly to the  boom.

Nine yachts in the Modern Sailing School & Club fleet are equipped with lazy jack systems. Only one of these has lazy jacks with no stack pack.


  • On larger boats, a mainsail can be very heavy and unweildy to handle, especially in high winds. When dousing, lazy jacks guide the mainsail into the stack pack and keep it neatly flaked on top of the boom - instead of flopping all over the deck. In San Francisco Bay, lazy jacks and stack packs are particularly useful, even on smaller boats.
  • Since a stack pack remains on the boom even while sailing, there's no separate sail cover to wrestle with and no need to fiddle with snaps or clasps at the bottom. After dousing the mainsail, simply zip up the stack pack and you're done!


  • When hoisting the mainsail, batten ends can get snagged on the lazy jacks. It takes a bit of caution and precision steering to raise the main without snagging it.
  • A stack pack adds windage that can detrimentally affect sailing performance to some degree. For many leisure sailors and cruisers, this is not a major concern.
  • Lazy jacks are not intended to replace the topping lift as support for the boom. Never loosen the topping lift to the point that the lazy jacks bear the boom's weight.

How To Hoist a Mainsail with Lazy Jacks

Your goal is raise the mainsail without snagging the battens on the lazy jacks. The trick is for the helmsman to watch the sail as it goes up, steer carefully, and use the breeze to help keep the mainsail in the pocket between the lazy jacks. 

  1. Steer the boat to head the bow into the wind. Keep the boat pointed as straight into the wind as possible. 
  2. Loosen the mainsheet and begin hoisting the mainsail.
  3. As the mainsail approaches the point where the legs join the risers, keep a close eye on the sail. If the wind is pushing the sail into one of the legs, steer towards the wind until the sail is luffing evenly between the lazy jacks (in the pocket) on both sides again. 
  4. If a batten gets snagged on the lazy jack, immediately instruct your crew to stop hoisting, then lower the sail until the batten is clear of the line. Steer the boat towards the wind just until the wind pushes the sail back into the pocket.

Additional Tips

  1. In "Hurricane Alley" (the entrance to Richardson Bay, the Sausalito arm of San Francisco Bay), winds often blow in a circular or erratic pattern, which can complicate hoisting a mainsail with battens and lazy jacks. Before hoisting the mainsail, check the masthead windex frequently to determine if wind direction is steady. If not, consider motoring to a location such as Racoon Straights or The Slot where the wind direction may be more steady. Note that heavy winds will luff the mainsail more vigorously, increasing the odds that you'll experience a snag. (Wind conditions and directions on the Bay may vary by season and weather.)  
  2. Never force a stuck sail by grinding hard on a winch. Excessive force could damage the sail, lazy jacks, or other components.

How To Douse the Mainsail

Hoisting the mainsail may require attention and skill, but dousing is a breeze - and the best part of sailing with lazy jacks!

  1. If conditions and crew size permit, send a crew member forward to stand in front of the mast and evenly flake the luff of the sail as it comes down. 
  2. Steer to point the boat's bow into the wind and loosen the mainsheet.
  3. If a crew member is at the mast to flake the sail, ease the main halyard in a controlled manner to facilitate flaking. Otherwise, simply douse the sail and let it fall into the stack pack.
  4. Zip the stack pack closed. That's it!

Additional Tip

If the mainsail didn't flake evenly into the stack pack as it was doused, the stack pack may be difficult (or impossible) to zip closed. If conditions at the dock permit, hoist and douse the sail again and stand at the mast to flake it evenly as it comes down. Also, it helps to tug the leech to straighten out the sail, if necessary.

Article by Mary Elkins on February 6, 2020

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