[Public-List] Main Halyard.

[John Birch]

Wire does make a difference and I've used both. Furlers still allow for 
stretch and stretch means the draft blows aft, not good. If you pump the 
sail up and leave it pumped - the shape will be ruined. Best bang for the 
buck remains wire to rope tail.

And furler guys, back off the tension when you get in.

Cheers

J

----- Original Message ----- 
From: "Bill Wallace" <wayfarer3134 at yahoo.com>
To: "Alberg 30 Public List -- open to all" <public-list at lists.alberg30.org>
Sent: Tuesday, February 25, 2014 5:19 PM
Subject: Re: [Public-List] Main Halyard.


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.
_______________________________________________
These businesses support your Association:
http://www.alberg30.org/store/A30supporters.html
Please support them.
_______________________________________________
Public-List mailing list
Public-List at lists.alberg30.org
http://lists.alberg30.org/listinfo.cgi/public-list-alberg30.org



 1393367495.0