2 Broken Kite Lines - 1 session?

[njrider]

Thanks all. We all have a lot to lose if we purchase "good quality" gear and get otherwise. I'm not suggesting that this is only limited to one company. However, I never had any problems with equipment that I used in the past (mixed brand names). I will post my video of my line strength tests and you are welcome to make of it what you will. If anyone feels that this is not adding constructively to a worthwhile conversation, I will stop adding any further information.

[tautologies]

When you say you haven't had problems with any other gear...didn't you post a whole thread and video about a liquidforce kite that seemed to be under inflated?

Either way I think what people and me included us that the lines used are fairly standard and neither of us had ever had that experience.

[njrider]

As promised...

[edt]

Love it!

can u do more tests? both them lines are way below 600. neither should have snapped like that.

[Bille]

As promised...
...

Do you have any Q-Power line to do that test on ?

Bille

[cglazier]

Nice effort njrider. I built a test jig like that and tested lines myself a while back. I learned a few things.

Most kite lines break well below their "rated" strength. It appears that there are different types of tests such as sudden impact and prolonged stretch and it is not clear which companies use when they quote ratings. But I found their ratings rather generous. Q powerline was no better than common hollow core braided spectra.

Breakages always occur near the line ends (clamp in your case) because that is where the line is weakened by compression. Strangely it always breaks about half an inch away from the end or the knot or the weak point. To truly test a line you need avoid weakening it at the ends. One way would be to have it gradually wind it around a very large diameter wheel (because any sharp bend severely weakens the line).

Incidentally I tested various knots and they all weaken the line greatly. Generally knots with sharper bends are worst.

I understand that the strongest line end is the sleeved and sewn loop which is commonly used on almost all kite lines. It supposedly maintains 90% strength. Any knot that you tie is far weaker.

As for which brand has the best lines.. ? No kite company makes their own line, they all source hollow core dyneema or spectra braided line from a very few suppliers. I would be surprised if you found much difference in standard line set strength between the top brands if you tested them all identically. ..Except North who use somewhat different lines.

CG

[Bille]

...
Q powerline was no better than common hollow core braided spectra.
...

CG

Dang !!
But thanks !!

Bille

[njrider]

If anyone has some broken line, I would be happy to test it - including any manufacturer who claims to use 600lbs line.

[edt]

nj message me your address i have line I can ship u to test out if you feel like it

[Johnny Rotten]

njrider....AWESOME!

I've been meaning to build a tester to test some of the lines I make.
Like your approach, and will likley steal some of your ideas for the rig I make.

I've done this for different board constructions and trying to keep this consistent to get meaningful results can be difficult by hand. Most tensile tests are done using a motor turning a fine screw at a set speed. Controlled electronically

Strain rate, ie the speed at which you move that jig will be EXTREMELY critical to the reading you get on the line.

If you're lines are total shit your current rig should be able to sus that out but. comparing different lines from different makers will be difficult to get meaningful results. I'm sure you could easily make one fail earlier than the other depending how hard and fast you pulled the winch even when trying to do it "the same"

Maybe you could replace the winch with a large threaded something and turn at a slow repeatable rate.

That stated the loads applied by the kite are not slow and smooth by nature so higher tensile strength under slow loading does not necessarily mean better lines for our intended purpose.

Some combination of slow controlled tensile test and shock loading would probably be the most relevant, to draw real conclusions but that gets complicated (or not depending on your creativity)

anyways, love the rig, love your approach not trying to piss on your results at ALL. Just some words of caution to avoid false conclusions.

I've also had a set of shit lines and broken 2 newish lines in a day and 100% confirmed no knots ....So attest that it happens...and am not refuting the fact that your Naish lines were likely shit.... My lines were liquid force circa 2008... avoided the brand ever since and am using Q power with great success and confidence.

That stated I have broken a stack of lines due to knots as well.....
when considering balance of probabilities, knots are usually the cause...I always check both ends before getting pissed at the manufacturer.

Still want to make a rig to get some idea of when it's time to replace lines and to test my stitching and joining methods.

What were your final failure reading for the LF and Naish lines?