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Old 16-08-2016, 10:17   #16
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Re: Minimizing stretch along Main's halyard

Top end race boat are still using dyneema, they have just switched to higher grades, really high end boats are using heat set sk-99 but that stuff gets insainly expensive very, very quickly and I would not recommend it to anyone that isn't sponsored, and racing at the very top end of world fleet racing.

While I generally agree with Uncivilized, no one has ever show actual creep in dyneema halyards. At the loads halyards see the amount of expected creep for even the cheapest dyneema is on the order of .01% line length a year. What happens is that as the line is loaded the findividual fivers set into place, and this causes the line to 'grow' just a bit. This is called constructional stretch and will happen every time the line is unloaded then reloaded and is noticeable.

To work it out you have to tension the line hard every time, give it a few minutes for the fibers to align, then trim it. The amount of constructional stretch is line dependent, but about 12" for 50'.

Note that all single braid lines do this regardless of material, so Kevlar, and vectran have the same issue. Dyneema is the worst in this regard because the individual fibers are so slippery the line moves the most.
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Old 17-08-2016, 04:47   #17
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Re: Minimizing stretch along Main's halyard

I really am thankful to all of you for your deep insight.

Indeed, no expert rigger here was in condition to tell me that much about ropes (people who sailed with P.Cayard...).

I really believe my dacron main is the culprit, and I will get used to re-tensioning the halyard a second time. :-)

I will look at my ropes with a different consideration, now on, and avoid twists every time....

Many thanks:-)

Gian
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Old 17-08-2016, 08:53   #18
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Re: Minimizing stretch along Main's halyard

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To work it out you have to tension the line hard every time, give it a few minutes for the fibers to align, then trim it. The amount of constructional stretch is line dependent, but about 12" for 50'.
Is it really 12" over 50'?
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Old 17-08-2016, 11:52   #19
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Re: Minimizing stretch along Main's halyard

It's simply nice to have someone who wants to learn. Not to mention who's grateful.
And the rigger comment is funny. Wonder if I know him?
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Old 17-08-2016, 12:01   #20
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Re: Minimizing stretch along Main's halyard

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Is it really 12" over 50'?
Crap no.

That number includes setting splices the first time. I just quoted the wrong note to myself. It should be about 1" in 50' for constructional stretch at reasonable halyard loads.But you have to harden the halyard past the sailing load every time you put up the sail.

It's exactly like a Chinese finger trap. When you ease the line to take down the sail it's like pushing the ends of the trap together. When you pull on the ends the next time first you get rid of the weave that has loosened up (constructional stretch), only then do you start loading the fibers.
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Old 17-08-2016, 12:09   #21
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Re: Minimizing stretch along Main's halyard

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Crap no.
I figured it was a typo Maybe 1.2"
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Old 17-08-2016, 12:14   #22
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Re: Minimizing stretch along Main's halyard

Maybe you need some mast bend?
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Old 17-08-2016, 13:06   #23
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Re: Minimizing stretch along Main's halyard

How will mast bend help with sail stretch, or taking the internal slack out of a halyard? Usually it's used as a mainsail tuning tool, & to adjust headstay sag to optimize jib shape.
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Old 17-08-2016, 14:59   #24
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Re: Minimizing stretch along Main's halyard

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How will mast bend help with sail stretch, or taking the internal slack out of a halyard? Usually it's used as a mainsail tuning tool, & to adjust headstay sag to optimize jib shape.
His post said "..I come up with a slack luff, by say 2"..." Which leads me to believe his concern is sail shape. Why would anyone be concerned about halyard stretch unless it's effecting sail shape?
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