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  #1  
Old 01-21-2013
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Halyard Stretch

Have been looking at the idea of all-rope halyards. It seems that there may be an error in the usual discussion over the amount of stretch in lines and an error in the way I have been thinking about rope for halyards. Line manufacturers use a % at load figure in their advertizing, like .7% stretch at 10% of rated load. This is a bit misleading. Once stretched with, say 500# of winch tension, the line will then stretch by an unknown amount. The line IS at its stretched length already. Any further stretch would only occur if more tension is loaded along the length of the line. Is there more load when the sail pulls? How much? I don't see much additional tension at all. Subsequent load it would seem is mostly on the slides, pulling at a right angle. Wind-induced tension is on the mast and slides not along the length of the halyard. So, the stretch argument seems to be a non-issue as long as the initial tensioning is enough to stretch the luff of the sail to its intended shape. Sails, of course, are sewn with the luff tensioned so as long as this tension is reached and maintained, the sail will maintain its shape. Can anyone shed any more light on this?
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Last edited by smurphny; 01-21-2013 at 08:25 AM.
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Old 01-21-2013
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Re: Halyard Stretch

When I raise the main in light airs the halyard tension is fairly low as is outhaul to produce a fuller shape. As the winds increase and halyard stretchs the main will start to "pucker" in between the slides. Additional tension is then needed to flatten along the luff. I don't know that I could put 500 lbs tension on to start, and since the line has a working load of 4 times that it would be about 25% of the lines stretch.
I'm probably unclear, but end result is all rope halyards appear to stretch and loosen as sail pressures increase unless you were overtensioned to start with.
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Old 01-21-2013
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Re: Halyard Stretch

Yes, that's what I'm questioning. If a sail has a bolt rope designed to be tensioned at X lbs., that is the right amount of tension to crank up when bending it on. I am wondering if there really is much additional stretch. The luff of the sail itself and the halyard are both at the same initial tension. How much overall stretch occurs after the initial tensioning and whether there is a significant difference between the percentage of overall stretch under additional load between wire/Amsteel/Technora, etc. vs a good piece of line with a higher stretch factor such as VPC or XLS. These companies want to get big bucks marketing high tech lines. I'm just wondering if there really is a significant, practical difference.

If I don't have enough initial luff tension, it makes a noticeable difference in close-hauled performance. I still have a wire-rope halyard. Am just wondering if using a "stretchier" rope halyard would result in not being able to maintain that tension.
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Re: Halyard Stretch

I've used XLS for halyards and it's OK but stretch is quite noticeable, on a cruising boat you just luff the main and tighten up and you can achieve the required tension. This weekend I crewed on a boat with very low stretch lines and when winds increased we did need to tighten on a windward leg. The stretch seemed about 1/3 to 1/2 of what I'd have expected from XLS under similar conditions. It was a 2 man job while racing because without luffing the main 1 guy had to sweat it at the mast while the other winched.
Stretch is a sliding scale as you pointed out, the percentage increases with load, so it really sticks out to you when you first switch from wire where the wire basically don't stretch at all.
There is a significant difference but doesn't seem worth the additional price for cruising.

Last edited by capttb; 01-21-2013 at 12:27 PM.
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Old 01-21-2013
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Re: Halyard Stretch

So....
Anything beyond "normal" sail tension requirements is overkill? How/where does one find that particular specification?
IOW..using more than required tension = BAD. What? Go30% beyond listed tension reqs for working load on halyard/other lines? 100%? 300%?
Inquiring minds wanna know
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Old 01-21-2013
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Re: Halyard Stretch

Quote:
Originally Posted by smurphny View Post
Yes, that's what I'm questioning. If a sail has a bolt rope designed to be tensioned at X lbs., that is the right amount of tension to crank up when bending it on. I am wondering if there really is much additional stretch. The luff of the sail itself and the halyard are both at the same initial tension. How much overall stretch occurs after the initial tensioning and whether there is a significant difference between the percentage of overall stretch under additional load between wire/Amsteel/Technora, etc. vs a good piece of line with a higher stretch factor such as VPC or XLS. These companies want to get big bucks marketing high tech lines. I'm just wondering if there really is a significant, practical difference.

If I don't have enough initial luff tension, it makes a noticeable difference in close-hauled performance. I still have a wire-rope halyard. Am just wondering if using a "stretchier" rope halyard would result in not being able to maintain that tension.
I've had wire, Stay-Set, and Kevlar halyards. If the sail and boat were designed for them, they all work fine.

Wire. Stays tight, tough on sheaves, hard to handle if no rope tail. But you know that part.

Stay-Set. For most cruisers it's fine. Yes, if the wind pipes up you might need to put a turn on the winch when wire or high-mod line would stay tight, but generally not. 90% of the time you can just winch it up tight and forget it. If you use a cuningham you will better served by wire or Kevlar that will stretch a polyester halyard too much. Expereince.

Kevlar/high-mod. Very nice and should outlast polyester. The only comment is that you must inspect the masthead and sheave for sharp spots caused by the wire.

---

Two personal observations: Don't spilice the end, just tie it on with a halyard knot or equivalent, either straight to the sail or to the screw shackle of your choise (no snap shackles). There will be some abrasion and this way you can trim a few feet every few years; don't buy Stay-Set X because the stuff still stretches and handles poorly to boot.
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Old 01-21-2013
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Re: Halyard Stretch

This is why I really like my wire / rope (spliced) halyards. Low stretch.
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Re: Halyard Stretch

Quote:
IOW..using more than required tension = BAD. What? Go30% beyond listed tension reqs for working load on halyard/other lines? 100%? 300%?
Because mainsail draft and depth are controlled by halyard and outhaul (ignoring the effects of vang, traveller and cunningham for now) there is no set tension other than balancing the 2 to create the shape you want. Some guys mark their halyards, first mark up to ten kts, second mark 10 to 15,etc.
Overtensioned is going to reduce draft and move it forward if outhaul tension matches, if outhaul too loose for halyard tension you get a wrinkle (sp?) running from luff to clew.
So, less tension the draft is deeper and farther forward for lighter airs, more tension the opposite to depower the main. You can sail in light airs with a drum tight main, it's just slower because your not getting the most out of the main for the conditions.
I've already committed myself as being more knowledgable than I care too here, as you get used to a boat you develop a feel for what tensions will produce the sail shape you want for conditions.
I'm NOT a sail trim expert but shape is everything, look at the sail, wrinkles, bags, sags means you got something wrong. Draft and shape on main and headsail should be pretty well matched up and balanced.

Last edited by capttb; 01-21-2013 at 01:33 PM.
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Re: Halyard Stretch

The other problem with stretch is variation when you want it least - for example, the wind strength increases, the halyard stretches, and the sail gets fuller - exactly when you wanted it to get less full, not more. This might be a worse problem in jib sheets, but I'm sure it affects the halyards too.
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Re: Halyard Stretch

I think there are 2 reasons we don't notice stretch on sheets as much as halyards Mark. First the halyard is twice as long so more stretch which is manifested by scallops along the luff and screams STRETCH ! Stretch on jib sheets is seen by breaking telltales or leech flutter and we just crank it in without differentiating whether caused from stretch or wind shift.
It does work just as you described and more bothersome at first but you adjust to it, and it only takes a minute to luff the main and tighten up.
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