[Public-List] Main Halyard.

[Bill Wallace]

Just to add gas to the flames, people should realize a couple of things about stretch - first the SAIL stretches as well, and it is polyester.  The other thing is that it is NOT the absolute stretch that matters - if the halyard stretched out an extra 34' as you raised it, but then was absolutely rigid once raised, it wouldn't matter, you just end up pulling twice as long (think of having a block arrangement to raise the main where you pull twice as much halyard as the sail height.  There are a couple of stretch related items that are important for mains - first, you never want to even get close to unloading the halyard - eg the halyard should never flap around, second the change in tension in the halyard due to tension changes in the luff should not cause significant length changes in the halyard.   It is this last point that people actually care about.

Now, the problem becomes knowing what the various values are and how much you care about sail shape.

The change in tension - this will be due to wind speed changes (gusts etc) and heading changes.  Anyone have a tension meter they could put on their halyard to measure this?  For standard 3/8" polyester double braid, each 100 lb change in force changes our 34' halyard length to the head of the sail by 5% * 100 / 2000  where 2000 lbs is half the break strength (Bool's law).   That is 0.25%, or 1".  With either 7/16" halyards OR Sta-set x (the stretch is the same), it would instead be 1/2".  The stretch with wire/hi-tech line is 1/4"  per 100 lbs.  Whether a gust load causes 100 lbs change in the halyard tension, I really don't know - I would guess it is between 100 and 200 lbs, so between 1/2" and 2" of stretch depending on material.    This value is for a hanked-on jib or a main.  Roller furled jibs generally do not exhibit much change in tension due to wind speed/heading changes - the luff is fully supported, so the horizontal wind force
 isn't translated into vertical force along the luff, only towards the leech.

This doesn't really tell us how to decide - for myself, I like my polyester halyards.  I can do a wire to rope splice, so the cost isn't much different.  I do race, but fairly informally.   It would mostly matter on higher-wind, gusty races because there, the difference in having a 1-2" flatter sail means the gust would spill off quite a bit better and I wouldn't heel/round up so much in the gusts.  Alternatively, maybe I will try sta-set x or 7/16" halyards (or both) if the 7/16" fits.  I might consider changing and see if it makes a difference.  First I have to see how my new main is this year :-)


Bill.
 1393366787.0