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SK99 line stretch

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ArneB
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SK99 line stretch

Postby ArneB » Fri Apr 02, 2021 10:38 am

Installed new 22M steering lines (SK99 1.6 mm 420kg break strength). Used Brummel lock splices at the ends.

After one session with very gusty wind (about 30 knots) my left line was about 10 cm longer (3.9 inch).

All the splices look good, also can't see anything visibly wrong with the line.

Never had this before, just wondering if this level of stretch is something to worry about...

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Re: SK99 line stretch

Postby Ventum » Fri Apr 02, 2021 11:22 am

Maybe the weave was not optimal when you marked the two lines.

Best method is to take one piece of 44m line, splice the ends, connect ends to a hook and apply 15-20 load via a balance wheel which you pull hard, then you mark the center which is the point where you cut and mark the other splices.
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ArneB
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Re: SK99 line stretch

Postby ArneB » Fri Apr 02, 2021 12:04 pm

Ah yes that could be, thanks.
The left line is red and the right blue, so could be that only on the left line the weave was not optimal.
Still a bit strange that it only happened on the 5th session, but that was definitely the strongest day with heavy gusts..

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Re: SK99 line stretch

Postby GuillaumeCoteMenard » Fri Apr 02, 2021 12:24 pm

It’s normal imho and I’m surprised you didn’t get more stretch out of them.

Just did mine with SK99 1.3 270kg. I did run some tests with 1m length just for fun. Initial length was exactly 1m (brummel lock splice both ends) that I pre-load by applying 10x a load of 100kg (1 min. of rest between each load). The line ended at exactly 1.021m. I let it rest for 1 day and it finally ended at 1.019m, which is about right with the tech specs that is 2% of stretch.

With that in mind, I pre-load all of my 4 lines (with the same load that i used in my test) with a binder. Harder to measure precisely the streching at this length, but i’m pretty sure i did get around that 2% again.

But it’s not a big deal for your line. You could give a good load to each of your lines. Remark them exactly equal and re-splice them.

Being on that subject, special thanks to « Foil ». I did my ClickBar following his advises and it went pretty good.
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Re: SK99 line stretch

Postby watercamper » Fri Apr 02, 2021 1:56 pm

Wow! 10 cm. I was looking at the Liros SK99 line at Green Hat Kiteboarding. It says it is pre-stretched. I talked to them. They don't load their lines prior to making a new set and said they have no stretch problems. Are there different types of SK99? Are some not pre-stretched?

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Re: SK99 line stretch

Postby slide » Fri Apr 02, 2021 2:19 pm

it might seem like an obvious question , but have you checked them on a stake it- is a test we should all do from time to time remove them and stake them
Last edited by slide on Fri Apr 02, 2021 2:42 pm, edited 1 time in total.

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Re: SK99 line stretch

Postby GuillaumeCoteMenard » Fri Apr 02, 2021 2:26 pm

I don’t know about GHK SK99, but 2% elongation at 50% of load is standard for SK99 kiteline:

https://www.marlowropes.com/system/fil ... download=1

With 10cm, you probably have loaded your line at around 10% of breaking load...

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Re: SK99 line stretch

Postby ArneB » Fri Apr 02, 2021 2:28 pm

Yeah checked it on a stake, definitely stretched.
Line is being sold as 'zero stretch'.

But 10cm stretch on a 22m line is 0,45% so maybe that falls within tolerance as previously mentioned.

Never had this with my front lines, even though they take more load.

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Re: SK99 line stretch

Postby Matteo V » Fri Apr 02, 2021 2:38 pm

watercamper wrote:
Fri Apr 02, 2021 1:56 pm
Wow! 10 cm. I was looking at the Liros SK99 line at Green Hat Kiteboarding. It says it is pre-stretched. I talked to them. They don't load their lines prior to making a new set and said they have no stretch problems. Are there different types of SK99? Are some not pre-stretched?
Always pre stretch, and never trust the manufacturer to do it.

Front lines need to be taken to a high load immediately prior to building the set. I've had the best results with the stair step method starting at 200lbs and increasing to at least 70% of breaking load then back down with 10 to 60 seconds at each increment, and about a half hour of rest on the lines so they "rebound".

For rear lines, I pre stretch 1 to 6 months prior to making the lineset. 50% of breaking strength is fine, with a "body weight" pull immediateltly prior to building the lineset.

Even with lower "SK" lines, I've not had any problems since implementing this procedure.

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Re: SK99 line stretch

Postby Jfactor » Fri Apr 02, 2021 5:46 pm

It's important to note that there's also a considerable amount of "stretch" the comes from the line compressing on the bury. When the line is first spliced, the fibers are pulled apart quite a bit just to get the fid inside. The splices settle a bit on the first ride. They should settle the same amount though, assuming the procedure was consistent between splices.


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