Thursday, March 27, 2014

Jib Halyard Tension, Big and Small

Earlier this month Peter Grimm from Super Sailmakers / Doyle Florida East flew to La Spezia, Italy to supervise the  sail reinstallation and testing on the 38 meter P2, a Perini-built, Briand designed superyacht that’s been making a name for herself in the international superyacht racing circuit.  The boat just underwent a refit, with some down-time to reconfigure some of the Doyle Stratis sails to adjust to a new halyard system.


Just like on any sailboat, halyard tension on P2 affects upwind pointing ability and speed more than any other control except the jib sheet itself.  The P2 team found their 1” diameter low-stretch Vectran halyard was stretching six inches over the 150 feet from the halyard cleat (actually, a 10-ton hydraulic piston) to the top of the mast.  The jib would start out looking great, but as the wind built, and the crew went through a few tacks, the halyard loosened, and sail shape reflected it.  The draft moved aft a little, some horizontal wrinkles developed, and the sailing angles suffered.  While the crew could tighten the halyard to compensate for the stretch and get it back to the desired height, the second and third rounds of tightening increased concern that something would break – and the costs of a “bang” on a 130-foot boat are often counted in millions, and injuries.  Another solution was needed.

Proposed P2 blade lock system
Peter coordinated with Robbie Doyle’s team in Salem, Mass., who provided the engineering and computer modeling to enable the spar modifications, and the sailmakers in Doyle Italy performing the sail changes themselves, to adjust to a new halyard locking system.  Like a Hobie Cat (just a little bigger), the new system terminates the halyard at the top of the mast instead of 150 feet later at the bottom, removing the halyard stretch variable from the system.  When locked at the top, greater luff tension would now be achieved through a removeable cunningham system that pulls from the bottom.  Great care was taken to ensure that the reconstruction of the tack area was engineered to ensure proper function, and when sea trialed last week, everything worked perfectly and the Doyle Stratis sails looked as beautiful as ever.  Now, P2 has consistent, repeatable luff tension.  Before, the crew needed multiple tons of halyard tension pulling up to keep the jib luff tight after stretching.  Now, P2 has a “set it and forget it” system requiring only a few hundred pounds of pressure to make changes – faster, safer, and simpler.

On any boat, proper jib halyard tension can improve performance, and make sails last longer.  Most sailors with furling genoas forget one important step with their halyard – relaxing it at the dock.  The proper halyard tension for sailing upwind in 15 knots, when left at full strength when the sail is furled up at the dock, will keep pulling on the luff of the sail, degrading shape and damaging the fabric, especially with laminated sails (even ones as long lasting as Doyle Stratis!).  We recommend briefly releasing the halyard cleat after the sail is rolled, allowing the sail and halyard to relax.  Then, when you go sailing again, you’ll probably wonder why there are horizontal wrinkles in the luff, and a big one at the pre-feeder.  This is a sign your halyard is too loose and requires tightening, easily done by luffing up with a loose sheet and a crank on the winch.  More fine tuning can be done to make the luff tighter for windy upwind work, and looser for light reaching, but this work can interfere with that rigid book-reading or wine-uncorking schedule, and may be considered optional.

On any size boat, proper jib luff tension can give you another few degrees of upwind ability.  On your boat, you probably don't need to spend tens of thousands of dollars to install a cutting-edge halyard lock system, but just think a little more about the systems you already have, and know how to get a little more out of them. If you'd like more info on simple things you can do to enjoy your boat more without spending a lot of money, give us a ring and we'll be happy to help.


1 comment:

  1. Peter,
    Interesting solution to age old problems (halyard stretch, mast compression reduction.
    But I wonder why the decision was made to have the lock on the aft side of the sheave axle. If the lock was designed
    to engage/disengage the halyard or extension of the sail's luff before halyard went over its sheave, then luff both the stretch & compression issues could be resolved with one fitting. Any post tensioning of luff could be done at tack or Cunningham at foot of sail.

    I suppose halyard induced mast compression wasn't considered to be an engineering issue. However a malfunctioning internal halyard lock is not easy to cure or maintain compared to an external version.

    Bill
    Sailing Specialties
    Odessa, Fl.

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