SJ23 Tech Tip F22, (Updated 2019-02-13) Bob Schimmel

Index

Mainsail Lazy Jacks and Storage Straps.
Call me lazy or whatever, but adjustable lazy jacks sure come in handy when you're ghosting along in hot weather and all I want to do is get out of the blazing sun, NOW!  OK they also work in a nasty blow but you get the idea that they simplify packing the mainsail by becoming the extra pair of "hands" you need.  Without them, the cloth is dumped all over the deck, creating a slipping and tripping hazard.  I prefer a clean "sticky" deck to keep me from taking a dive into the murky depths, thank you very much.  Prior to my lazy jack system I've come way too close in fulfilling this disaster!  But that's another story.  The solution is pretty simple as shown at right.  I've used it for many years and the only complaint I have is occasionally snagging a batten when hoisting the main sail.  It's usually a matter of feathering the mainsail into the wind between the jack line, then a quick pull on the halyard as the batten passes a jack line.  Sometimes easier said than done!

CONSTRUCTION - Panache's upgraded lazy jacks (2019) are made from slippery Amsteel Blue Dyneema.  1/8" for the jack lines and 3/16" for the halyard portion as shown in the diagram.  Three jack lines provide more support than my previous two shown in black. 
Dyneema line is too slippery to hold a knot so a loop was spliced in the end that slips under each eye strap on the boom.  The eye straps are pop riveted on the side of the boom above the clew reef lines running along the side of the boom.  They are positioned between the existing red sail straps.  The high position of the eye straps ensures the bunched up sail cloth can't push down against the reef lines, causing extra friction on the reefing system.  Remember to add a glob of sealant under each eye strap before it is riveted to the boom.  If you screw them, it is best to tap thread in the boom for machine screws.  This way you can easily service the system should you have to replace a line.
A low friction SS eye is spliced at the junction point of each line so the lower jack line can easily slide through it.  For maximum strength the angle formed at the throat of an eye splice should be 300 or less which results in loosing only 10% of the line strength.  To splice a loop in single braided Dyneema use a locking splice with two loose ends or a locking splice with one side attached.  While not actually required I added a whipping over each splice to secure the SS eye from breaking free and damaging the sail cloth.  Umm, I don't need that, especially where I can't reach it!

The loose end of the jack lines is secured to a cleat mounted on the front of the mast.  Position the height of this cleat above the clew of the jib so the sheet can't snag on it.  While this snag occurs more often in light air tacking, is it ever a nuisance when sailing in close to other boats.  A snag happens less often in anything more than a moderate wind.

New lazy jacks in place and ooooh does the sail drop nicely to stay on the boom.  At right the lazy jack halyards through the blocks at mid spreader.

 

 

 

 

 

 

 

 

 

 

 

 

 

CONSIDERATIONS

  • 2021 - To prevent snagging a batten at the leech as the mainsail is hoisted I spread the tops of the lazy jack halyards part by running each through a small block secured to the mid point of a spreader.  This is a departure from running the halyards over the spreaders close to the mast, as I previously did.  I just have to remember to pull a messenger line through each block before I lower the mast, otherwise the blocks are out of reach when I raise the mast.  Tape the end of the messenger to the end of the jack halyard and hoist the messenger, pulling it through the block.  Works very well.  Spreading the lines also minimizes chafe on sail cloth and will not affect sail shape. 
  • Alternatively, install two lines (not shown) to pull the middle of the lazy jacks forward of the mainsail leech while hoisting the sail.  Once hoisted, the lazy jacks can be released to contain the mainsail when it is lowered.
  • If you like night sailing, consider using day glow lime green jack lines or parachute cord with day glow inserts to improve visibility.  Forget about slipping unseen into an anchorage at night then!

JACK LINES - 32' of 1/8" Dyneema with 2 matching SS thimbles, 8 eye straps.
HALYARDS - ~44' of 3/16" Dyneema with 2 matching SS thimbles to reach the cleats on the bottom of the mast. 
NOTE: Add 6" for each eye splice in the line.

LAUNCH - Install the boom on the mast.  Tape the end of the halyard to the messenger line and pull through the spreader block.  I loosely tie both halyards to the cleat on the front of the mast.
HAUL OUT - Fan fold the mainsail on the boom and secure with the straps to the boom.  Tape the messenger line to the jack halyard and hoist the messenger line through the spreader block and detach from the lazy jack halyard.  Secure the messenger to the mast and tuck the lazy jack line under the sail straps.  The messenger line stays with the mast and the lazy jack lines stay with the boom.  Slip the sail cover over the boom and spiral wrap a line around it.  Remove from the mast and tuck into the cabin.

OPERATION - Once the mainsail is dropped between the lazy jacks, I pull the leech aft to straighten the fan folds.  Then I snap the four straps around the mainsail to secure it to the boom. 

 

 

 

 

 

 

 

 

 

 

 

The straps are permanently sewn around the foot of the sail so I never have to look for them.  The length of each strap is cut to fit loosely around the sail.  Sometimes I clip them to each other under the boom.  The black plastic clips can be found in a camping supply store.

See Tech Tip F05 for Reefing Line Systems.

 

 

 

 

 

 

 

 

____________________________ PREVIOUS SYSTEM ________________________________

My previous lazy jacks consisted of two lower 3/16" soft nylon lines looped under the boom as shown at right.  Between them they contained the loose mainsail on top of the boom, sort of.  The lower split lines were pulled up tight by the 3/16" halyards that go over the spreaders and down the forward side of the mast where they were fastened to the spinnaker ring on the mast track.  These halyards never snagged laying over the spreaders and always stayed next to the mast.  I used soft nylon line to protect the sail cloth.  Anything bigger than 3/16" is overkill and is extra windage. 

Each jack line went through an eye strap under the boom to keep it in place and was pulled up on either side to be divided into two equal loops (port/starboard).  It is important to run these lines against the boom, inside the reefing lines, so as not to affect the 1/4" reefing lines along the boom.  The eye straps were positioned at the 1/3 points along the boom.  Your mainsail may have different requirements so be your own judge in this.

I tied the end of the halyard to the junction point of the jack lines where it bisected the angle of them.  While this supported the mainsail for many years, when relaxed they hung just low enough to slip the sail cover over the boom.  This was more luck than by design because I forgot to consider the sail cover in my design.  Anyway, if you have this problem it can be alleviated by using a tiny block at the junction point so the halyard can center itself along the jack lines and hang lower.  Alternatively, tie a loop at the end of the halyard and slip the jack line through it. 

The free end of the halyard was tied to the spinnaker pole ring on the mast as shown above.  Just before I put my mainsail cover on, I slid the ring to the top of the track, which creates just enough slack to fit the sail cover on.  If you don't have a spinnaker ring on a track, devise an alternate method to secure and loosen the halyard.  When sailing, the ring was positioned with just a slight amount of slack in the lazy jacks.  This way the mainsail shape is not distorted and can generate the most pull.  In this position it contained the mainsail and the whisker pole was quite happy with it. 
 

Return to Tech Tip Index. . . . . . . . . . . . . . . Have a Question?