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Line strength for hydrofoiling ?

Posted: Sat May 12, 2018 9:49 pm
by Peter_Frank
I know this topic might have been put up before, but I couldnt find it...

If making a longer lineset for marginal winds, from say Cyclone Pro-Line / Dyneema or similar, and one want them thin, what would be a reasonable strength to aim for ?

I was thinking 170 kg front lines, and 100 kg for rear lines (for the average weight) at first.

But maybe 130 / 70 kg is sufficient, or even 100 / 70 ?
Or 130 / 100 to have a margin ?

The frontlines are each mostly taking half the load only, whereas the rear lines are not loaded much except when looping (which one does a lot in marginal winds)

Any thoughts and experiences ?

Or, a pointer to the thread I assume MUST have been earlier, if covered before :D

"Normal" kitelines are typically 250 to 300 kgs or so, but that is a totally different ballgame as this is very powered and for jumping in higher wind, and they are hugely overkill for foiling, let alone marginal wind foiling :roll:

8) PF

Re: Line strength ?

Posted: Sat May 12, 2018 11:08 pm
by TomW
I set up a bar with 1mm sk99 line from premium ropes that has 280 kg limit. They seem really thin compared to Mt new Ozone bar lines.
They are much softer too.
So I'm afraid to depend on them.

Re: Line strength ?

Posted: Sun May 13, 2018 3:34 am
by downunder
Here is the last thread:


My view is horses for courses...

Re: Line strength ?

Posted: Sun May 13, 2018 9:18 am
by Foil
It has always been a concern of mine after snapping a line during a high powered jump, which resulted in an out of control decent dropping like a brick.and this was days after my buddy did the same, when I got home I removed the complete line set for a little experiment,
Securing one end of a 3 yard length around a gate post and the other around the hook of an old harness bar,
Holding the bar with both hands and leaning back to tighten the line I quickly snatched back on the bar,
The line broke after a few hard snatch pulls I repeated this a number of times and was in disbelief at how easy it was to snap the lines by loading up very quickly,
This did remind me of once when I was on the beach with my old C kite from 2001 and it fell back into the wind window and I could tell it was going to power back up, in them days I did not have a quick release so dug my heels in and sat down ready for the kite to yank me down the beach,
To my surprise the sudden pull snapped 3 lines.
For me you get what you pay for nowadays, look at slingshots 500lb line, that will take some punishment 🤔
Q line pro was very very good, also in choice of colours, but the cost and availability was a problem, but easy to cut your own lines, the parks head knot had to be replaced every so often, but that was easy.

Re: Line strength for hydrofoiling ?

Posted: Sun May 13, 2018 9:41 am
by Peter_Frank
Thanks downunder :thumb:

Some information in that thread, definitely, but also some "Quababble" he hee.

It was not very hydrofoil specific, so I would like to continue here (will change the title).

Also, I am not talking about the rear lines only - as most of us have WAY less load on the front lines when hydrofoiling.

Yes, the thinner rear lines are no good for reverse launch on land, which is often the only way to launch a light LEI kite in marginal winds.
But this can easily be addressed using a tad longer leader lines :D
This would be good anyways, so avoid lines getting cut if the hydrofoil should come into the lines - eventhough it doesnt really happen in these winds so not an issue.
Also, a hot launch LE up can be used instead, better in such really low wind.

I have never ever broken a "normal" line the last 15 years, and use them for some years (4 or more ?) kiting, but have several bars so of course not the same wear (but I get to ride 200-250 kites yearly so some "wear" :naughty: )
Only in the very early years, having some very low quality lines with doubtful origin, I had broken one in a (not very powered) TT jump, and also cut two frontlines when crossing lines on the water with another kiter :roll:

Some lines can get a bit of "fray" at the sleeving ends, if one is very harsh on the lines (rolling them towards yourself when packing up, instead of walking towards the lineends which is better), or if starting on tough ground.
But then you can just cut a bit of the end and they are good as new.

Disagree that only racers and not "freeriders" want thin lines.
Particularly when using long lines, it matters a lot more.

And why would we not seek the ultimate and best, or at least on some points no matter what our other choices are ?
Freeride is not the same a being a casual weekend warrior who dont care much about things, IMO.

Using a carbon bar, no safety, no heavy pads, lighter suit, lighter kites, low drag lines etc etc, in marginal winds :rollgrin:

This is why I was thinking about something like, for average weights (one has to scale accordingly to own weight):

170 /100 kg.
130 / 100 kg
130 / 70 kg.
100 / 70 kg

It might be more than sufficient, and it might also be on the verge to break relatively easy ???
The highest load will come if a kite falls and catch up again on the way down - can happen in marginal winds, eventhough less load.
One could choose to "eject" the kite if this happens, if fast on the trigger, you will have to swim/drift ashore anyways in this wind.

It goes for both foil and LEI kites, same thing IMO, that thinner lines are a good thing.

I know this is impossible to say for sure, but there must be some having experiences with thinner lines and having broken these and in which circumstances, just to get an idea.
They might have to be changed more often (or not if flown till they break, in safe surroundings of course).

8) Peter

Re: Line strength for hydrofoiling ?

Posted: Sun May 13, 2018 10:13 am
by TomW
I'm not a math person, but know that F= MA.
F is force in Newtons, M is mass in kg, and A is acceleration in m/s.

You can then look at it 2 ways.
1. The kite pulling your body up out of water or for a jump.
F= 80kg x 2ms = 160N.
You might say your body is moving faster.
F= 80kg x4ms = 320N
Or you are pulling up water too:
F = 100kg x 2ms = 200N

2. Your body might be fixed point, and kite is exerting power against it. How much force can a kite produce in the scenario of kite luffing and regaining power suddenly?
This seems to me the most likely failure. It could easily be 400N or more.

Now remember you have 2 lines, but might not be equally stressed at some moment.

Finally, lines are rated in kg. Which is confusing because it must really mean Newtons.
So seems to me that 280kg rated lines x 2 lines is sufficient for 80kg foiler.

You might say you need 2.5x safety margin, then the 500kg lines make sense.

Re: Line strength for hydrofoiling ?

Posted: Sun May 13, 2018 10:51 am
by Peter_Frank
I know, but I dont see it this way, as it is an unpredictable load that one can not foresee anyways...

When our "normal" say 270 kg lines are more than sufficient in all scenarios (for me no matter how hard they get spanked in TT jumping or looping), then they will be WAY overkill for foiling IMO.

Indeed a kite luffing and regaining power can break almost any line yes, just as even a strong kite flying LE down first can get tomahawked into two if unlucky.

But in "normal" riding diving or looping the kite to start, I think there is a substantial margin when in 5-7 knots of wind, especially the rear lines.

Thus interested in experiences also, but most dont have this I think, as racers need strong (AND thin) lines so they are restricted more, and most others use their normal lines, just longer of course, or extensions.

Regis is one of those with experience I know, eventhough a lighter rider than average :thumb:

Of course difficult, but if several got experiences where the lines sometimes can be too weak for normal hydrofoil riding, then one can always choose an overhead strength based on own choice, and live with the risk of them snapping.

Knowing that the lines have a VERY different breaking strength, even the very same lines, so of course not valid - but better than nothing.

I am an engineer calculating on almost everything - but important to know where this isnt of much or no use at all, and experience a lot better :D

8) PF

Re: Line strength for hydrofoiling ?

Posted: Sun May 13, 2018 12:15 pm
by downunder
I have no idea how I'm surviving on a super thin custom lines and had 4 kites on one bar over last 2-3years. 200 sesh/year.

Number of records on Woo for a given day, 60kg, never ever snapped a line.

But sure, would drop as a rock when LE exploded, luckily was only launching. LE is good example coz it is not 300% overdesigned as the lines are. Imagine that blader!

I mean, we discussing thin lines and FS boost has super thin back and front bridles, and that kite is specifically designed for boosting.
How thin, dunno, thinner than Edge, hence can be even 25-30% less then Ozone.

I recon 70kg for back is fine. Risk is no different than any other risk with this sport. Cutting fingers? God, If anyone tried to cut one line with a knife it takes quite some effort to cut a thick line. Thin line way easier to cut. So, what's the real risk? I know one death by lines around the neck, which we can't prove.
But we know of one near death by lines around the ankles. The photo exist, I have it and know the person.

Also know the person who kited for at least 30km unhooked, when his harness broke.
He was riding FS Psycho back than on open waters infested by sharks in the Shark Bay.

The point is, we cant plan for everything. We can put a lot of faith in something but than else will happen. The line might give away when least expected, no matter what.

That's why I love it.

Re: Line strength for hydrofoiling ?

Posted: Sun May 13, 2018 12:34 pm
by cwood
I would not play at the margins for strength. I broke 3 normal newish flysurfer lines at once on an aggressive downloop while landing a boost on my speed5 12m last year. Let go like a gunshot. Broke a bone in my hand from the recoil into my spreader bar. Out for a month.
Read about Gunnar's recent crash and being knocked out cold from one steering line breaking.
This is a dangerous sport at speed with intact equipment. Throw in a failure and it can be deadly.

Re: Line strength for hydrofoiling ?

Posted: Sun May 13, 2018 1:54 pm
by downunder
we discussing a HF riding, with no loops and 10m jumps, in very LW.

U love looping? Buy a tick lines. U love racing, buy super thin lines, u are a pro anyway, no leash or safety.

I'll repeat, most kiters never attempted to cut the line, not to mention different ones. Thin lines are easier to cut. If never in the situation to cut the lines how would one know what's more dangerous?
On that note, the bar should be shipped and instruction given on cuting the line. And it should be practiced but are we doing it? No. But, that's safety, we are not discussing it now ;)

Any sport at speed is dangerous, play chess than (not you obviously).