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Speed system / mixer test explanations

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Mossy 757
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Re: Speed system / mixer test explanations

Postby Mossy 757 » Mon Apr 23, 2018 4:37 pm

foilholio wrote:
Mon Apr 23, 2018 3:07 am
Having run many a pulley line to destruction, replacing them for shrink is wasteful. Sheathed line has a wonderful soft failure where the core can remain intact for quite a while after sheath failure, noticeable as a rough point when sheeting. You can get stuck pulleys and other bad things happen or even full failure, best avoided if you can. I know the furry and thinning signs of a pulley line that is about to go so I usually replace them. But even with full failure I have ridden the kite in. Kite still works somewhat with just A and Z intact, another safety advantage of foils over tubes.

You have 15 years designing making kites, congratulations. There is many many kite designers/makers who once made for some well known brands, now they don't and most just do repairs. Ever wonder why that is? I can see you are knowledge in kite construction techniques, somewhat in design, but adjusting kites particularly old ones not so much. Also your understanding of fluid dynamics is well flawed, and that's a hint to the previous question to think on.
I don't want to make any commentary on your level of knowledge, but recommending people ignore fraying pulley lines because they have a core is not a recognized best-practice for safe kite use and maintenance. If the pulley lines are shrunken to a degree where the mixer cannot be adjusted to make the kite fly sufficiently well, they should be replaced regardless of their physical degradation. I mean, we're talking about a few small segments of line that are available for purchase ready-to-install for a few US dollars. That, to me, is a perfectly reasonable expense if I can no longer properly tune my kite.

I'm not sure if you're aware of the tone of your posts, but I'll make a couple of observations and hopefully it will be helpful for you:

1) You and Kitexpert totally ruin threads when you pull this BS. For people coming in here looking for a good-faith explanation of how to maintain their expensive purchases, you guys bring this discussion in totally the wrong direction - away from simple, safe, easy tips and tricks into some kind of crazy in-depth conversation about fluid dynamics that isn't merited. We should trust that Armin did his homework and that what we need to discuss is the practical lengthening or shortening of lines.
2) From a 3rd person perspective as a fellow foil kite owner/tuner, Kitexpert is making more sense in this thread than you are. It's possible that I might that way because I lack your level of knowledge on the topic, but given my background and education, I think that's unlikely. It seems to me that your advice is of a lower quality and less clearly articulated than his. If you wish for people to value your input on the forum, you should reflect on that before launching personal insults and attacks his way publicly.

kitexpert
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Re: Speed system / mixer test explanations

Postby kitexpert » Mon Apr 23, 2018 7:19 pm

My apologies. I know there has been unnecessary arguing in which I've been involved too. I do write sometimes a bit harsh, partly because english is not my own language and also because I tend to get annoyed if I'm pushed to it.

But I don't hurt my feelings so easily and actually I like people like foilholio who are a bit "fanatic" and willing to test and tweak different things. Discussion may not be clearest but there is a possibility to face some useful things or ideas, something worth trying. My own approach has usually been quite practical and trying to keep it simple, that is true especially when it comes to bridles and speed systems. For a long time I've been trying to make them as short and simple as possible. Actually I would have liked to get more adventurous with some design parametres but for me it would have been too risky because of labor and material costs.

"Fluid dynamics" is too theoretical for working with kites which are not high performance wings. It isn't needed or it is too difficult to use it (computer simulations etc.) beneficially for kites. If someone knows how to achieve any essential value by theoretical approach I'm very interested to hear it.

From design perspective I'm just pleased simple mixer (1:2:4) works so well and also that I've reached good enough knowledge how to design optimized bridles. Then it is possible to concentrate "real questions" of kite design.

-----

Problem with kite lines changing their lengths is not simple by its nature. Changes are different in different parts of kite and some affect to AoA, some camber, or both. Many fixes are simplistic, they do improve kite flying but at the same time can cause other problems or decrease performance or make it more difficult to deal with coming issues. I've seen kites with extension lines, added LCL's, shortening knots, replaced low quality lines etc. so that kite looks messy (and is out of tune) - then it is not so nice to begin adjusting it.

foilholio
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Re: Speed system / mixer test explanations

Postby foilholio » Tue Apr 24, 2018 2:52 am

Mossy 757 wrote:
Mon Apr 23, 2018 4:37 pm
recommending people ignore fraying pulley lines because they have a core is not a recognized best-practice for safe kite use and maintenance.
No that is not what I am recommending. I am recommending they do replace for fraying or more particularly heavy fraying, but not shrink. If you were to carry the logic that lines should be replaced because of shrink you would swap out the flying lines and entire bridle every couple months. What I am pointing out is pulley lines breaking on foil kites is not anywhere the big deal it is on inflatables, I think those who are new to foils from inflatables carry that fear for which is reasonable for inflatables but not foils. I have dealt with broken pulley lines 20 plus times on water, plus broken lines, plus bridles and kites and many other things. I know something about gear failing. You shouldn't really kite in situations where gear failure will risk injury or life, but if you do you need to maintain your gear to a higher level.
Mossy 757 wrote:
Mon Apr 23, 2018 4:37 pm
I'm not sure if you're aware of the tone of your posts, but I'll make a couple of observations and hopefully it will be helpful for you:
I am and it is not good but you can choose to ignore them.
Mossy 757 wrote:
Mon Apr 23, 2018 4:37 pm
1) You and Kitexpert totally ruin threads when you pull this BS. For people coming in here looking for a good-faith explanation of how to maintain their expensive purchases, you guys bring this discussion in totally the wrong direction - away from simple, safe, easy tips and tricks into some kind of crazy in-depth conversation about fluid dynamics that isn't merited. We should trust that Armin did his homework and that what we need to discuss is the practical lengthening or shortening of lines.
Correct we do ruin it and maybe I should just let his BS pass, viewer discretion and all. Armin does know his stuff, but the mixer is in need of a update.
Mossy 757 wrote:
Mon Apr 23, 2018 4:37 pm
2) From a 3rd person perspective as a fellow foil kite owner/tuner, Kitexpert is making more sense in this thread than you are. It's possible that I might that way because I lack your level of knowledge on the topic, but given my background and education, I think that's unlikely. It seems to me that your advice is of a lower quality and less clearly articulated than his. If you wish for people to value your input on the forum, you should reflect on that before launching personal insults and attacks his way publicly.
Congratulations. Well in the threads where I have started and explained things only to have the "kitexpert" do the opposite, well good luck. Please choose to ignore my posts. My experience can tell what "kitexpert" has absolutely no idea what he is talking about ( which is some things not all !), but hey new religions are started all the time.

Regis-de-giens
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Re: Speed system / mixer test explanations

Postby Regis-de-giens » Tue Apr 24, 2018 6:58 am

I feel that Foilholio remarks are pertinent and worth taking into deep consideration. However as topic ignitiator i think that such debates actually requires long argumentations to e accurate and not adapted in this post if we want to keep it fluid and tool box for overall user.
I kindly ask you open new threads on specific debatable topics and focus here on "Overall admitted" points ? Hope it concludes this phase of personal debate.

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Re: Speed system / mixer test explanations

Postby kitexpert » Sat Apr 28, 2018 12:23 am

Regis-de-giens wrote:
Tue Apr 24, 2018 6:58 am
... focus here on "Overall admitted" points ? Hope it concludes this phase of personal debate.
I guess the problem with kite tuning mainly exist because there is two (or three) different things there: 1)AoA change 2)camber change (and 3)porosity). Many kiters don't know how tell the difference between them in how kite flies, for example if kite backstalls too easily it may be because of too high AoA or lowered camber/distorted profile (or bad internal pressure).

If all three issues are present it can be a real challenge even for an experienced kiter. Porosity is by far the most serious problem, because it is universal (affects everything) and it is difficult to fix.

To keep it simple I suggest to isolate different parts of the kite, which are 1)flying lines 2)mixer 3)bridle. And it is usually wise to try to go back to the factory settings rather than starting to make a lot of own tweaks which can be a nuisance after a while and a source of new problems.

Some kites would benefit redesigned bridle (and sometimes different mixer) but it is another story. Some designs can't be helped much or not at all (for example Pansh Aurora).

It should be remembered that mixer is mostly a tool to control AoA of the kite, to make it possible to adjust power/depower by the bar movement. Nowadays most kites use 1:2:4 mixer, which is a "straight" system which don't alter camber much (depends on line row locations - which are usually quite balanced) and to some degree how tight Z is. But if Z is very tight some effect of mixer is lost (foilholio calls this "high(er) camber", I call it foolish adjustment). BTW no production kite has something like it but in fact more opposite, kites come with quite loose Z. That is because if Z is too tight kite becomes twitchy, less controllable, bar pressure increases, sudden backstalls etc.

General advice is to understand different parts of kite and their functions. Then it shouldn't be too difficult to get along with adjusting foil kite.

Regis-de-giens
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Re: Speed system / mixer test explanations

Postby Regis-de-giens » Sat Apr 28, 2018 7:53 am

I add herebelow a variation of the "bad" case 3 with its setting on A :Image
This is for example how the MT of the Conceptair Pulsion is built : you can see that the green SPL B line is now connected above the adjustable knots and not below.

This is (very) interesting because shortening these knots maintain a smooth higher camber profile (C +1/2 B) AND at the same time decreases the Angle of Attack. This is great for a light wind kite because in marginal wind it is useful to increase the camber (=>more power and later backstall) and trim a bit at the bar (=>avoid backstall). At least that is what I do in extreme light wind.

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Re: Speed system / mixer test explanations

Postby kitexpert » Sat Apr 28, 2018 2:05 pm

Regis-de-giens wrote:
Sat Apr 28, 2018 7:53 am

This is (very) interesting because shortening these knots maintain a smooth higher camber profile (C +1/2 B) AND at the same time decreases the Angle of Attack.
I don't know if it is very relevant how AoA is decreased, usually it is done frontline/backline adjustment (bar position, trimmer, preset). There is a practical limit to low AoA, kite either collapses or if it is stable it just won't go any lower.
Regis-de-giens wrote:
Sat Apr 28, 2018 7:53 am
This is great for a light wind kite because in marginal wind it is useful to increase the camber (=>more power and later backstall) and trim a bit at the bar (=>avoid backstall). At least that is what I do in extreme light wind.
Sounds reasonable. But even better would be a kite which has higher camber so tweaking wasn't necessary and shape of the kite would be cleaner, not distorted by bridle/mixer adjustment.

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Re: Speed system / mixer test explanations

Postby foilholio » Sat Apr 28, 2018 2:37 pm

kit expert wrote:
Sat Apr 28, 2018 12:23 am
Some designs can't be helped much or not at all (for example Pansh Aurora).
Rubbish
kit expert wrote:
Sat Apr 28, 2018 12:23 am
It should be remembered that mixer is mostly a tool to control AoA of the kite
An oversimplification. No it changes camber as well. AoA also changes with flying.
kit expert wrote:
Sat Apr 28, 2018 12:23 am
because if Z is too tight kite becomes ... sudden backstalls etc.
Absolute rubbish. With Z tight you get less backstall not "sudden backstalls". Let me help you I think you mean "sudden frontstalls". You can't even get your front and back stalls associated correctly, the mark of not an expert at all.
kit expert wrote:
Sat Apr 28, 2018 2:05 pm
I don't know if it is very relevant how AoA is decreased, usually it is done frontline/backline adjustment (bar position, trimmer, preset). There is a practical limit to low AoA, kite either collapses or if it is stable it just won't go any lower.
The hunt for more depower is the holy grail of foils. Amazing thing is to disable part of the canopy.

kit expert wrote:
Sat Apr 28, 2018 2:05 pm
But even better would be a kite which has higher camber so tweaking wasn't necessary and shape of the kite would be cleaner, not distorted by bridle/mixer adjustment.
Interesting you just discount the biggest advance in parafoils, and that is the sewn shape doesn't need to match the bridle shape. Suggesting that kites adopt high camber in sewn is just crazy, those are all old old designs so hard to use and in fact almost lethal to use. I think it was paragliders that most famously made use of the reflex profile sewn, maybe Peter Lynn or some kiters were doing something earlier tho, I will say it is competely at home on kites where stable high depower is a must.

Kit expert you really come off as some has been kite draftsman from one of those little known brands with big ego ( I sense that being thrown back at me :-) ). It feels like you just come here scraping for fresh ideas . Gathering how your ideas have change in your posts I think that is correct.

kitexpert
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Re: Speed system / mixer test explanations

Postby kitexpert » Sat Apr 28, 2018 3:59 pm

Mixer does not necessary change camber at all, and least of them does it most used 1:2:4 mixer (or 1:2), which are linear ones (I wrote earlier "straight"). By designing line row locations in certain way some camber change is possible though, but it is not very much. If you'd understand foilholio what I've explained here you could see it immediately by looking any modern foil kite.

It is completely different thing there is a possibility to adjust camber in mixer, and the main reason for that adjustment is to counter pulley line shrink, not to adjust camber. For example Ozone doesn't even have that possibility.

Pansh Aurora is not a very good design in the first place and even worse to improve it. Some tweaks are for sure possible, but I meant something more than that.

It is just funny if you foilholio think I don't know what front stall and back stall means. It is a fact if you have tight Z and you sheet in your kite will backstall, even fast - and why on earth this trivial setup isn't more used if it was any good?

If kite (sewn) shape does not match bridle shape result is distorted shape (bends, creases, bulging etc.) It means more drag and less performance. Exception is high AoA flying when added camber is more useful than distorted shape, because drag is very high in any case.

If you think low camber kite tweaked by mixer to high camber is somewhat better than kite with that same high camber "sewn in" you are wrong. Every part of that tweaked kite is wrong shaped for that new camber, every single part.

Finally, it is simpler than you think foilholio. I just know foil kites inside out, every part and every function of them. Unfortunately I've not had any new ideas here, at least so far. Bridle or mixer tweaking are not very relevant questions in kite design.

Regis-de-giens
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Re: Speed system / mixer test explanations

Postby Regis-de-giens » Sat Apr 28, 2018 10:51 pm

I agree with foilholio on adjustable mixer. On top of compensating for wear (It is a pitty that Ozone has none), it can actually extend the wind range of a kite by : higher camber in low end and flatter camber in high end for exemple. Or it is also a way to adapt to the personal ride condition of each rider : irregular / turbulent wind => you can set less camber to increase stability in detriment of lift. On the contrary on a site with steady wind =>you can increase camber to bring additional pull in low end or get less backstall in lulls (Kite flying backward to ground).

The limit of a too high camber is the instability in frontstall (Kite collapsing).

To me the "easier" way to optimize a kite (for newbies to foilkite set-up) is to increase the camber little by little up to start feeling instability in frontstall. And then you can punctually shorten a bit B and C in high end of the kite to both decrease its power and reduce the risk of kite collapsing. Useful in hydrofoil in particular.
Last edited by Regis-de-giens on Sun Apr 29, 2018 1:47 am, edited 1 time in total.


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