J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Main halyard/sheaves

I had the rig unstepped yesterday to sort out this sheave issue and do some other needed maintenance. I have a write up of yesterday's work along with a number of photos here: http://www.rambunctiousracing.com/mastwork.html

The primary reason for dropping the rig was to find out what was jamming and cutting the main halyard and to fix the problem. I assumed that it was a sheave issue. The real cause surprised me.

The main halyard runs through two sheaves and then drops into the mast. The first sheave is in the mast crane. The second sheave is in the center of the mast. The second sheave serves to guide the halyard down into the mast without chafing on anything.

At some point in the past, the secondary sheave (the one in the mast section) seized. Its bearing was caked with dirt and the sheave would not rotate. Rather than remove the sheave and clean or replace the bearing (which is nothing more than a small bronze sleeve), it was decided to simply bypass the secondary sheave. Bad, bad idea.

Rather than running cleanly into the mast, when the second sheave was bypassed, it ran against the top of the mast extrusion, inside the channel for the mainsail's luff. As it was a wire halyard, it carved a sharp-edged, v-shaped groove in the soft aluminum. Truly, I can't think of a more efficient shape for jamming and cutting line. The photos below show the groove with the messenger line caught in it. With the new sheaves in place, this groove will be bypassed, so the problem is solved. Also, the groove is far too small to have any effect on the strength of the mast.

The two photos below show the groove carved by the old wire halyard:







[This message has been edited by Jason King (edited 08-12-2007).]