I need convincing too:) Bar back lines!

[Matteo V]

Really quick, and I'll address the rest of your post directed at me later:

Do you understand the concept of wear over time vs breaking strength. Specifically the example of 200kg lines worn to 50% of their original strength yield 100kg breaking strength, and 300kg lines worn to 50% of their original strength yield 150kg breaking strength?

Take that down to internal abrasion at a sleeved loop - 200kg lines worn to 20% of their original strength yield 20kg breaking strength, and 300kg lines worn to 20% of their original strength yield 30kg breaking strength.

I think I do "know" you and your are thinking "that is only a 10kg difference". But that is 1/

Hmm,

You are hard man to argue with. Ffs I am not talking about degradation, what this has to do with line strength ?

People answered and you are not accepting the fact:

- it is possible to use super thin back lines.

How thin? We don’t know simply coz we don’t know how much we pulling.

Stop hiding behind general answers we all know. We passed that point years ago.

The question is simple: how much we pulling?

Stop before u answer since the question is not about the safety you are pushing as your argument.

I will repeat, if your argument is safety the bladder should be rated to 100psi or more. But it’s not. The bladder is also degrading and abradding...enough said.

I see your reply now, you are avoiding to answer again with generalisation we all know.

I have no idea what you are talking about a bladder degrading and abrading. I have thousands of hours under inflatable kites and have never had anything other than valves not sticking because of inferior glue, or strait up blown leading edge (not bladder) where the bladder did explode out once the integrity of the leading edge failed. I hope I do not have to explain that one to you. If so, could someone else here help me?

Safety is a concern with lines at extreme low strengths. Again, Flysurfer feels it necessary to comment on that at 160kg back lines. But wear is the biggest concern for me. Again, I will refer you to the (my) last post on page 3 of this thread. How long your lines last to a minimum breaking strength is determined by many factors, beginning with how strong they start out as.

Can you answer my question about your comprehension of multiple variables?

[downunder]

You are again patronizing, however with a bit of 'toned' response, which is slightly better. But still not polite enough. It can be learned, not to worry.

In response to???

I am not trying to berate you because I very much appreciate your post. It adds discussion and gives kiters an idea of the mentalities/ideas out there. So thanks and keep posting.

So you see insincerity in my advice? Please understand that I am sincere, and I even tried to head off you going in this direction by mentioning the fact that I was not trying to berate you. I am also truly sorry that I have "triggered" you and absolutely do not mean to patronize you with this statement either.

And let me be candid with you –

If you ever find yourself in a frame of mind such as “everyone is against me” or “this person is out to get me”, drop the emotional side and just look at the reasoning, logic, and evidence that person or those people are presenting. Your emotions on this issue are of no help to you in finding the answer. They are actually doing the opposite and/or they allow you to be manipulated. Someone attacking you personally typically indicates a weakness in their position. I would not do that in this case as I am trying to help you understand the answer to your question. And I would admit I am wrong before I would result to such personal attacks, or even a subtle attempt to "patronize" you.


As for your additional questions -

The perception of 'pulling weight' with the bar is wrong when I think of it:

- same rider, high pressure on the bar. Is he/she pulling more weight on the bar?
- same rider, light bar pressure would indicate LESS weight?! How? The rider is the same?

You gotta clear this one up for me. I am totally lost with what you are trying to say. Are you talking about different kites? Or are you talking about perception of bar pressure?

Then, if you can, pleas explain what the heck these statements mean???

You Matt can at least show appropriation for this ppl coz they are pushing the boundaries in this sport. Not you I'm afraid, you just follow (apologies if not, but that's how it sounds).

and

NO JUMPING means NOTHING in my books.

Too many reply’s, apologies, did not see this before.

Of course different kite! That’s where different bar pressure is coming from, right?

No jumping means nothing coz:

- what is a jump by someone’s standard?
- the rider weight in a jump on the same lines/ kite?
- wind strength

This are variables we don’t know for lines to use as an argument.

So before we use it, we need to agree what they are, if not, it means nothing for me.

I’m surprised you do not see that but just follow what ozone is telling you ( now you are referring FS, so you lowered your standard by 20%, how come?) . That will not lead into a new discoveries and pushing the barriers....

Again it is not about you, and your concerns with safety.
Remember, years ago you would run thick lines just because everyone else did.


I admit, I have absolutely no clue how much we pulling on a bar, and what is high/low bar pressure...Not convinced, sorry.

Not one single answer was presented except 5%.

[Ozone Kites AUS]

In the mid-1990 s, PSR developed a patented recrystallization process for converting
Honeywell s S-900 fiber into a higher strength material. The Plasma process produced
ropes that were the highest strength constructions available, predating the availability of
ropes made from either S-1000 or SK-75. PSR s patented Plasma process involves
realigning the molecular structure of the Spectra fiber under a combination of precisely
controlled tension and elevated temperature. This procedure not only produces a stronger
fiber but also ensures that all of the individual filaments within the rope component being
processed are the same length, thereby maximizing fiber efficiency. In order to control
the process with a high degree of precision, the Plasma process is carried out on a subcomponent
of the finished rope (i.e. a strand or other twisted component) rather than the
entire rope.
One of the primary elements of the patent is the method used to heat all of the fiber
filaments uniformly. This involves complete immersion of the manufactured rope
component in a hot liquid bath. Synthetic fibers are poor conductors of heat.
Consequently, the only way to make sure that all of the filaments are heated to the same
temperature is to use a hot liquid to penetrate throughout the fiber bundle. Any other
type of heating will not produce the desired results.
Heat-Set Ropes
Since its development, Plasma has been extremely popular in a wide variety of
applications due to its durability and strength. In recent years, other rope manufacturers
have attempted to duplicate the results obtained from the Plasma process by utilizing a
heat setting technique. However, heat-set ropes are produced by running a strand or rope
under load through a forced hot air oven, not the liquid bath that is a key part of the
Plasma patent. The hot air heats up the surface of the rope but, because of the poor
thermal conductivity of synthetic fibers, the interior of the rope does not reach the same
temperature. Consequently, this type of process is only partially successful at best.
There is some increase in initial strength, but this is due primarily to the high loads used
to process the rope. This load in effect work-hardens the rope, not unlike the initial
increase in strength obtained from a new rope if it is tensioned repeatedly for several
cycles. However, the uneven heating also produces a rope with unequal fiber lengths
throughout the rope s cross-section because the interior of the rope will not be heated
sufficiently. This produces uneven load sharing throughout the rope s cross-section that
will adversely affect the rope s strength efficiency and overall performance. In
conventional double-twist braided ropes, especially in the larger sizes, there is already an
inherent imbalance between the outer yarns in the strand and those in the interior. Heat
setting of the rope can make this imbalance more pronounced. Another byproduct of this
process is a stiffening of the rope structure due to the high loads placed on the rope
combined with the hardening effects of the dry heat. It is important to note that Plasma
ropes are not heat-set and do not exhibit any of the adverse performance properties
associated with this type of procedure.

* * *

The above is from a data sheet by jeyco summarizing some of the technology used creating spectra. Dyneema is created using a completely different process and because of it the molecules are not as well aligned as spectra. The repeated resistance on Dyneema aligns the molecules and strengthens the rope. When you look at repeated testings of break loads for dyneema if you start doing the test at a lower load and then ramp up they give you a higher load than if you break it right away. At least that's what I remember.

Anyway correct me if I'm wrong, but of course, spectra and dyneema are very similar and for our uses we can consider them identical.

https://eurofibers.com/mooring-ropes/
and
https://www.cortlandcompany.com/product ... ring-lines

The article you posted is referring to very high loading ship and barge mooring lines. Both companies websites above claim "worlds strongest" which is a bit confusing, and sort of understandable, because essentially the two products are the same.
The lines we are using for kiting are similar in chemical structure, but the high load ropes have been given some special, expensive treatments due to their specific application. Visit this site and I think you will find that DSM have their own patented technology to make super strength Dyneema too http://www.dsm.com/products/dyneema/en_GB/home.html

RE, the OP's question - you can go as low in strength as you like, probably 100kg or less on your rear lines, but good luck! Any wear, slight increase in loading, wind gusts, would result in a broken rear line and death loops galore! Manufacturers have over the last 20 years worked out best available compromise. Most brands are running 200-300kg rears, because they give good performance and a high degree of redundant load capacity in regard to user safety. Most front lines are in the 350-500kg range now, for the same reasons, except front line loads are higher.
I'd guess 99% of people kiting do not want super thin rear lines, kite racers being the exception and they have explored pratical line lengths and strengths, most will use as short as possible and a strength compromise in 100-200kg range for their rears and 250-300 on their fronts. But they do break lines, and they lose a race when they do, so they are very careful not to go too light and will change lines frequently.

[Matteo V]

I’m surprised you do not see that but just follow what ozone is telling you ( now you are referring FS, so you lowered your standard by 20%, how come?) . That will not lead into a new discoveries and pushing the barriers....

You brought up Flysurfer. And I explained to you that you missed the fact they they specifically do not recommend you jump with 160kg rear lines. So I cannot use them, nor can anyone I know use them because we all jump, even on hydrofoils so long as we are strapped! Thus the default of Ozone's recommendations of 200kg. Or give any Joe on the street more credibility than Ozone if you wish?

And now you don't want to talk about jumping because there are too many variables??? You are going around in circles and I am chasing you. Still fun though!

Again it is not about you, and your concerns with safety.

I will stop an idiot on the beach from hurting others, but not themselves. I will do my best to explain to an idiot what is going to happen to them if they continue on the path to disaster. Still, I believe in freedom, and anyone's quest for a "Darwin award". Just don't get my beach banned in your pursuit of it. Even if I am there, I likely can't stop you from hurting yourself, but I will try. If I am there and you are intent on doing something that will hurt others, I WILL STOP YOU. This is SAFETY!

[downunder]

^
Simple question, what is a jump for you? But I just told you, we, who are using super thin lines would be all dead? Would you really stop Nico (world Champ), before he jumped 10-15m on FS race lines in front of 500 people? Would you? Common, be real and ask yourself that question.

Coz FS is saying not for jumping that does not translate into not doing it. We passed that point long time ago. We pushing the barriers. We, who do not follow but create our rules. You follow. Not we. That's is the core of everything. This sport did not evolve around safety, but pushing the barriers.

You are just avoiding the question and going on safety topics, at.al. Which I hate because it is opening a can of worms. And I'm running in circles, but mate, you did not answer any of my question? We can't even agree on what the jump is? Funny....

I know what jump is in my books, ok. The jump in my books is everything higher than I'm scared off. That constitutes a real jump. For me. Everything else is not a jump to be scared off. Because man, the line can break even if you don't jump. The line can break even if never ever used before. What is here not to understand? If you're putting a lot of faith in lines, I can assure you, the bladder might explode when you do scary jumps and lead you into your death.

Trust me on this, ok, the moment the industry makes ultra thin, non stretch and high load lines, some people will use it asap. Simple as that. Some people are using it now, we told you that, they told you that, but you are going on and on about safety. Your safety or what you perceive that is safe around you. The World is not spinning around you, fortunately. It comes again on you being an authority, which you're not. Not to me anyways.

Whow, and you didn't not know about bladder abrading? How about the Ozone strap on tips which we discussed many many times. I hope people will explain better, coz, you know, you're using English, which is not my first language, to convince everyone to your thinking on the German site. Don't tell you did not know Toby is German and this site is in Germany?

Good one you edt, a lot of useful info you're presenting here. Refreshing.

[foilholio]

Do you understand the concept of wear over time vs breaking strength. Specifically the example of 200kg lines worn to 50% of their original strength yield 100kg breaking strength, and 300kg lines worn to 50% of their original strength yield 150kg breaking strength?

Take that down to internal abrasion at a sleeved loop - 200kg lines worn to 20% of their original strength yield 20kg breaking strength, and 300kg lines worn to 20% of their original strength yield 30kg breaking strength.

This is a good point, I think margin for age must be a strong design factor. I have tested quite a few bridles on foil kites and the do break at about 50% of rated strength when old. There is also the connection method and I have tested sleeves vs splices and splices are quite a lot stronger. What I have seen in use though is wear at the connection point is the most likely cause of failure for which a bare splice can be worse especially if you disconnect-connect lines which I would not consider with splices. I have had 12 or 8 strand front lines hanging on by just 2 strands, there is a lot of margin there.

One thing maybe more particular to foil kites is that with reverse flying and especially with a WAC line the rears can be loaded a lot more, but I would say at most this would be 40kg and usually only 10 to 20kg.

Another thing is the bar ends and bars are usually weaker than the rear lines.. guess which can break?

For my 'extremist light wind' configuration (on my 15m and 18 m kite, 60kg rider), I use 70 kg rearlines ; clearly it is only adapted to light wind hydrofoil on foil kite without jumps nor unhooking, but it works. You can save some 100 gr , you gain some drag , but above all better control of the kite thanks to less rear lines curvature which is quite important on depowered a foilkite (even if the elasticity will increase a bit and be detrimential to the control).

On big kite you have less dynamic/peak effects (slow loops, progressive line retensions, slower crashes if any) so you can risk thinner rear lines IMO.

I think people need to factor in your lightweight Regis with such weak lines, while the lines are still new that strength is quite practical.

I do think elasticity is an issue as you go weaker, but then maybe a benefit for the more relaxed riding as it would smooth out gusts! I do think kite designers looking for the more instant response and feel ,which would originate from there international pros, well then high strength lines would be more desired and would explain why brands like Slingshot have such strong lines.

100grams saved, most inflatable riders would probably laugh but in the crazy lightwind some foil kites can fly this really makes quite some difference.

lines get stronger with use as the dyneema molecules gets more and more aligned in the same direction, but that's why not why they weaken, they weaken because every time sand rubs against the lines, or you twist them on to the bar, or you make a turn, the lines fray and wear, that's where they get weaker. There's also a little bit of UV degradation but dyneema is pretty good against UV. Spectra of course has some mechanical stuff done to it which pre-aligns all the molecules so unlike Dyneema which gets stronger with use, Spectra always get weaker with use just from the UV. Anyway, I'm saying yeah you're right lines don't really degrade over time from using them as lines. It's all the other stuff that puts wear into lines. I don't know how it's possible to care for lines and make sure they never get fuzzed up I don't think it's possible? Maybe you can do it, I can't. Thinner lines of course wear faster so need to be replaced more often. The only exception to this is q-power which only wears right at the knot.

There is really very little difference between Spectra and Dyneema, both are just trade names for UHMWPE or Ultra-high-molecular-weight polyethylene, Spectra is owned by Dupont and Dyneema by DSM. I've never read anywhere that the fibre gets stronger with use. Spectra and Dyneema are hardly affected by UV, I have a set of flying lines made from Spectra that are now 20+ years old and they seem as strong as they ever were.

Have a read of this

https://en.wikipedia.org/wiki/Ultra-hig ... lyethylene

From my research the difference between Dyneema and Spectra is just names. My experience with plastics is they all degrade with UV, ones that have no UV protection degrade fast and ones that do then degrade slower. I have seen plenty of Polyethylene, much thicker than any kite lines that has UV protection turn to crap. I think the only way to prevent UV degradation is to coat the outside in something that completely blocks it.

little searching.

https://onlinelibrary.wiley.com/doi/abs ... /app.12448

Abstract

This study investigated sunlight‐simulated ultraviolet (UV) beam irradiation on the tensile properties and structure of ultrahigh molecular weight polyethylene (UHMWPE) fibers. The tensile results showed that after 300 h sunlight UV irradiation, the tensile properties of the UHMWPE fibers were obviously degraded. Investigation of morphology revealed that the crystallinity was slightly increased, whereas the overall orientation and molecular weight of the fibers were decreased. SEM observations indicated that the degradation process was nonuniform throughout the fiber and a change from a ductile to a brittle fracture mechanism was found after UV irradiation. DMA results showed two β‐relaxations and one α‐relaxation in the original single filament, and UV irradiation led to the increased intensity of the high‐temperature β‐relaxation and the lowered position of the low‐temperature β‐relaxation. This indicated that irradiation‐induced molecular scission and branching were located primarily in the amorphous and the interface areas of the fiber. Changes in the thermal behavior were also examined by DSC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2757–2763, 2003

As I said kite bridles break at about 50% with quite some age, I think kite material is similar. While I do see perhaps up to 5% of fur from broken fibers in the bridles, I would put most of the strength loss down to UV or Sunlight.

The above is from a data sheet by jeyco summarizing some of the technology used creating spectra. Dyneema is created using a completely different process and because of it the molecules are not as well aligned as spectra. The repeated resistance on Dyneema aligns the molecules and strengthens the rope. When you look at repeated testings of break loads for dyneema if you start doing the test at a lower load and then ramp up they give you a higher load than if you break it right away. At least that's what I remember.

Anyway correct me if I'm wrong, but of course, spectra and dyneema are very similar and for our uses we can consider them identical.

Yep no doubt they have different manufacturing processes, but there is plenty of examples of things produced with different methods with much the same product. If you cut something with a laser or a cutting bit you still cut it right? In this case you have the same material UHWPE achieve the same desired property, high tensile strength, through the same material structure, molecule alignment. If one has more UV resistance than the other you are looking at dyes and coatings which is just another thing being done.

Safety is a concern with lines at extreme low strengths. Again, Flysurfer feels it necessary to comment on that at 160kg back lines. But wear is the biggest concern for me.

Something to add the 160kg lines are for their race kites, which are foil kites. Foils through perhaps their less rigid structure, many bridle lines, higher mass(inertia) and maybe aerodynamic properties deliver much lower peak forces or simply have much smoother power than inflatables. They miss that hard kick in jumps, (but they do go higher and further ).

Safety is a concern with anything that is weaker, safety is it's biggest concern over land there we find land kiters using even weaker lines than water kiters :-/ Now usually it is guys that don't usually jump or jump high.


Lastly I will say to you both to take individual circumstance into consideration. A 50kg rider is safer on 160kg lines than a 100kg rider on 200kg and even 300kg. Every rider has different risk, land, water,snow,ice,grass,concrete, kiteloops in 50knots, hydrofoil kelp keeping in 5knots. Manufacturers are just guarding against liability. Anyone who wants to go outside manufacture guide lines should stop and think and get to know what and why.

Now I have said my piece, just wait till the "kitexpert" arrives and we can make this 100 pages lol.

[Matteo V]

^
Simple question, what is a jump for you? But I just told you, we, who are using super thin lines would be all dead? Would you really stop Nico (world Champ), before he jumped 10-15m on FS race lines in front of 500 people? Would you? Common, be real and ask yourself that question.

Ok. If I saw his lines were down to two strands, even with 200kg or more rear lines, I would make sure he knew that he was not safe to use those lines. I would not stop him with force, but I would try to stop him by convincing him. But that is only at an uncrowded beach where he could only hurt himself.

At my beach, local or destination, if he was launching in tight quarters with innocent beach goers or other kiters within 2.5 kiteline legnths, I would stop him with every means possible. If I did not, my beach would be banned. So there are the two answers to your questions that are logically consistent with my policy. Come to my beach and try me.

Coz FS is saying not for jumping that does not translate into not doing it. We passed that point long time ago. We pushing the barriers. We, who do not follow but create our rules. You follow. Not we. That's is the core of everything. This sport did not evolve around safety, but pushing the barriers.

This statement in bold is beyond reasoning. I almost can't even think of a way to tackle that one without an analogy. So here is my best shot. The country in which you live says you should drive on the proper side of the road. Can you drive on the other side and go against traffic? Well, yes, so long as there is no traffic and you do not get caught. So why don't you? Because if you do you are really f-----g up things for the other drivers out there. Just because you can do something, does not mean you should.

And you think you are leading? You are way behind the crowd on extremely small diameter lines. But more over, you don't need them, because you don't race. And the actual benefit to smaller or extremely small diameter lines is minuscule. I mean we are talking 1°-2° more upwind performance on a high resistance board (TT or surfboard) and likely a bit more with a low resistance board (hydrofoil, or ice kiting). The biggest problem with your idea is that you think you are gaining even a slight advantage in everyday riding, but you are not. The second biggest problem is that you think no one has done this before, or that everyone should be doing this. You are way out there on this. Again, not a personal attack, just a statement of your place with respect to experienced kiters and the general kiting population.

And so this sport did evolve with safety as do pretty much all sports. I would love to see your reasoning behind your position against that. To help you, here is some of my reasoning that kitesurfing evolved around safety.

1. Kitesurfing was first attempted by those who had kites that would sink. So in those early years, almost no one kitesurfed. Then the Legaignoux brothers invented the inflatable kite and it became safer to self rescue and get your gear back without ditching it out to sea. More people started to kite and push the limits given the numbers of participants and accessibility.
2. Safety releases were virtually non-existent at the beginning of kiteboarding so no one wanted to risk being connected to a kite they could not release under load when it got out of control. Then came the CL release and kiting became safer and more people started looking at kiting as an "almost as safe" alternative to windsurfing.
3. Then the bow kite was introduced that increased (eventually) the safety of handling of the kite, and the ability of the kite to handle a range of wind speeds. This was especially important as kiting was not feasible (no upwind capabilities) at inconsistent wind locations where windsurfing did work well. And so the safety innovation of the bow kite being able to handle a range or wind speeds marks when kiteboarding exploded into popularity.

Many more example exist, and kiteboarding's past is littered with bad ideas (safety mistakes) that have become footnotes in kiteboarding's history. I think you are onto one of those mistakes with thinking small diameter rear lines are for everyone. You will get beaches banned with that line of reasoning. I feel bad for those kiters that behave responsibly and follow manufactures recommendations. And let me throw this back at you, "Ffs don't try dumb experiments in close proximity to others on the beach!

We can't even agree on what the jump is? Funny....

I know what jump is in my books, ok. The jump in my books is everything higher than I'm scared off. That constitutes a real jump. For me. Everything else is not a jump to be scared off. Because man, the line can break even if you don't jump. The line can break even if never ever used before. What is here not to understand? If you're putting a lot of faith in lines, I can assure you, the bladder might explode when you do scary jumps and lead you into your death.

This is the definition of "subjective". An subjective is ok for you, BUT YOU WANT OTHERS to nail the forces in the back lines for all kitesurfing circumstances down to a few kg??? No one would else would define a jump as "higher than I'm scared of". I will give you that may fit "bosting", but not jumping.

Let me help you with an objective definition of jumping. Honestly, I never thought I would be typing this out -

1. Chop-hop - leaving the surface of the water via popping (quickly stepping on the tail) the board or using a wave/wake as a ramp WITHOUT help from the kite. In this circumstance, the kite does not add significantly to the ultimate height gained over the water before coming back down.
2. Jump - Leaving the surface of the water with kite power as the primary or secondary (wave or wake can assist) source of upward pull.

In depth explanation of #2
Jumping is when the kite's upward force is greater than the force of gravity on the rider. Noticeable heights are achieved by the total upward force of the kite exceeding approximately 1.25 or more times the weight of the rider. This puts more load on the lines than just the riders weight as the upward force of the kite must be enough to accelerate the kiters weight upwards. This force of acceleration takes into account the amount of time the force is acting upon the rider. So for a given height, the speed at which it is achieved, affects the maximum force exerted by the kite (and thus the force exerted by the lines).

Not subjective, but full of (non mental) variables none the less.

Trust me on this, ok, the moment the industry makes ultra thin, non stretch and high load lines, some people will use it asap. Simple as that. Some people are using it now, we told you that, they told you that, but you are going on and on about safety. Your safety or what you perceive that is safe around you. The World is not spinning around you, fortunately. It comes again on you being an authority, which you're not. Not to me anyways.

No authority is given to anyone beyond the integrity of their argument.

For example; I can teach a parrot to say that "squak, the sky is blue, the sky is blue". The parrots statement is not invalid because it said by a parrot. Or would you argue that because it is only a parrot, you must dismiss the statement as false?

I never wanted to be "your authority". My only goal is to help you with the question you have asked. At this point, I am pretty sure I have failed, as have others. But that is ok. Very few people get things "right off the bat". You will likely learn in time.

Whow, and you didn't not know about bladder abrading? How about the Ozone strap on tips which we discussed many many times. I hope people will explain better, coz, you know, you're using English, which is not my first language, to convince everyone to your thinking on the German site. Don't tell you did not know Toby is German and this site is in Germany?

Yes, that is a kite brand/model specific issue. None of the kites I have ever owned, nor have I ever seen a kite have that issue. All the kites I have owned or seen have had the canopy deteriorate before any LE issues with the following exceptions:

1. Faulty sewing of the LE (not bladder) caused the LE to open up on 1 model of kite I briefly owned and the bladder explode out of it. All of these kites were recalled and the LE stitching was reinforced.
2. Valve glue of inferior quality was used causing the valves and strut connectors to peel away from the.

And your English is good. So much so that I was afraid to ask if it was your first language or not. Informing me of this has cleared up some syntax issues I have had with your posts.

So please ask again any questions you feel I have not answered to your satisfaction. But before you do, try to look up what "multiple variables" means and how not all questions have only one answer for every circumstance.

[Matteo V]

I do think elasticity is an issue as you go weaker, but then maybe a benefit for the more relaxed riding as it would smooth out gusts!

Rear line stretch will depower the kite in a gust. But it will also reduce response time for sheeting in as those rear lines stretch. And there are 2 kinds of stretch, elastic and in-elastic. In-elastic stretch is the stretch that causes your lines to go out of tune resulting in one somewhat permanently being longer than the other.

Elastic stretch is even more of a problem on front or back lines. This type of stretch is like a rubber band as it "springs back". So think about using a bungee cord for your back lines - you would have much less control, if any, for sheeting AND steering with springy rear lines. If your front lines are "springy" they can even steer the kite one way or the other depending on how the back lines stall out one side of the kite and reduce power delivered to that same side front line.

Front line stretch will POWER the kite in a gust. This is the reason why low stretch lines are integral to kiteboarding on long lines. Extremely short lines reduce the total travel for a given load/percentage stretch. But this mostly works out as LW kiting is done on long lines, and high wind kiting is done on shorter lines. - just a note, I only use 23m lines for every size kite and like NOT having a different power stroke in light vs high wind.

Something to add the 160kg lines are for their race kites, which are foil kites. Foils through perhaps their less rigid structure, many bridle lines, higher mass(inertia) and maybe aerodynamic properties deliver much lower peak forces or simply have much smoother power than inflatables. They miss that hard kick in jumps, (but they do go higher and further ).

Safety is a concern with anything that is weaker, safety is it's biggest concern over land there we find land kiters using even weaker lines than water kiters :-/ Now usually it is guys that don't usually jump or jump high.

I started out on foils and still use them on the snow. Foils are as varied in feel as inflatables, maybe even more so. No blanket statement can be made about the characteristics of all foils. Though I will give you the fact that most modern ultra high aspect ratio foils (the ones you have to carefully watch for bridal stretch) do have a similarity amongst themselves akin to the similarity shared between all bow kites.

And foils have a more rigid structure than inflatables. This may seem counter intuitive, but it is directly tied to the full support of the underside of the kite with the bridal system. Foils, when they are filled with air and not stalled, do not "cone" like SLE inflatables. This is likely the reason for the difference in the general feel of "power" between a foil kite and a SLE inflatable. Also, the warping induced by turning the kite is very much even at every wind speed for foils due to this rigid support. SLE inflatables have a variability in how they warp, due to depower tuning and partial stall in the turn, that is both an assert and a liability at the same time.

[edt]

Thanks for all the info on spectra and dyneema. I'm always trying to learn more. I was sure that the methods used were quite different and caused slight differences in the lines, but I could have been wrong. It's a little bit weird talking about snapping lines like it was some disaster. I've snapped at least a dozen lines, spreader hooks, ripped out attachment points, snapped boards in two, torn bridles and never felt like gear failure was a problem, except during a downwinder, that sucks when you have to hitchhike back to the launch or walk it out from the planet of the apes. You hit the QR, sometimes full release and swim in. Go as thin as you like. BTW I have never snapped a line just boosting, it's always on take off, crash or a megaloop (there you do want thick lines of course). If you are boosting on land . . . ok that's dangerous, you want thick lines. I hate boosting on land that shit is scary. Watching those land boarders megaloop is crazy stuff. Maybe also if you are boosting 20 meters+ on water but that is world record territory, I don't think I've ever boosted that high. Also if you are snow gliding. I would never snow glide that shit looks suicidal and I would never do it, but makes a good video. If you are boosting in 25 or less knots why not try some 100kg lines. If they snap you swim in. Make sure there's nothing downwind of you of course. The last time I saw some line testing is when a kite crew tied their kites to the top of a van drove down the beach and measured the pull with the kite over head on the rears and centers. That's the only way to put a real number on this stuff otherwise it's just guessing. We do have G measurements on the woo and stuff like that and it ranges between just up to between 2.5 and 3G's or so, once you get the percentage of pull that the bar gives, you take the kite out with a woo G measurement (only use the take off G's not the landing G's obviously) and there you have the exact amount of pull the rear lines take. Personally I like thick lines, 300-400kg fronts and rears for me.

[Regis-de-giens]

Considering the huge loading difference between a 60kg rider on a foil and a 100 kg freestyler, it is really not optimum to use a similar line combo. This is to me the limitation of bar standardisation. Pratical and economical for kite brands , but necessarilly dimensionned for the worst demanding style and heavier riders or obvious safety reasons . Hence FS option for thin rear lines 160kg (with appropriated warning) ... and that everyone can easily understand are still oversized for a non-racer lightweight foiler in low end ... in 1t years of kite I never changed any line and got no breaks ever.

I do think elasticity is an issue as you go weaker, but then maybe a benefit for the more relaxed riding as it would smooth out gusts!

Rear line stretch will depower the kite in a gust. But it will also reduce response time for sheeting in as those rear lines stretch.

Elastic elongation depends on the ratio Force / diameter ^2. As a consequence on foilkites with most of the load going to the front lines , if you use same diameter for front and rear lines , you will get a higher elongation on front line in gust ... which will power-up the kite... during gusts => not great !
To me diameter shall be balanced with force repartition.

Side note : To limit wear during loops on my rear thin lines, the first 2.5 meters (near the bar) have higher diameters and then connnected by splices. And final connection to the kite is done by a dyneema loop of higher diameter to keep the thin line straight only.