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Foil Kite tuning tips

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Re: Foil Kite tuning tips

Postby kitexpert » Mon Jul 16, 2018 6:37 pm

sabraxas wrote:
Mon Jul 16, 2018 6:05 pm
can you explain how camber of profile is changed when aoa is changed lineally?
Yes, I've already done it several times. When kite is designed line row locations and mixer pulley ratios are chosen for desired effect. Camber can be unaffected, it can be increased or in some weird tweakings even decreased when kite is powered up (AoA increased).
sabraxas wrote:
Mon Jul 16, 2018 6:05 pm
And how arc and projected área of Foil Kite is changed?

Thanks
This is much more difficult question. Nowadays PA on most foil kites is not changed much if at all. Psycho4 had it most, but it resulted a bit weird handling/bar feel. I haven't seen a pair of pictures which show this effect in Soul, or is it there at all. Armin says it is, but I haven't seen %'s of different PA's or proof in real life.

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Re: Foil Kite tuning tips

Postby sabraxas » Mon Jul 16, 2018 7:08 pm

Thanks for explanation. I own speed 4 Lotus, specification say PA is changed from 70 to 85%. Thats teorically.

A friend owns Psycho 4. You can adjust profile and flying characteristics by opening and closing an internal zipper that affects internal inflation pressure.

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Re: Foil Kite tuning tips

Postby kitexpert » Mon Jul 16, 2018 7:53 pm

sabraxas wrote:
Mon Jul 16, 2018 7:08 pm
You can adjust profile and flying characteristics by opening and closing an internal zipper that affects internal inflation pressure.
That is true. To have it as strongly evident as it was in Psycho4 there are many things involved. At very low AoA (when fully depowered) stagnation point moves (partly) above air intakes and internal pressure decreases. Apparently this helps kite to have more canopy curve and less PA.
sabraxas wrote: I own speed 4 Lotus, specification say PA is changed from 70 to 85%. Thats teorically.
Yes, for sure it is difficult to measure exactly how much PA changes. I'm not sure how much FS has had benefit for this invention, other manufacturers (except ConceptAir ?) don't advertise or have it. All PL arcs have it because of their structure, C-kites also.

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Re: Foil Kite tuning tips

Postby foilholio » Tue Jul 17, 2018 2:22 am

direnc wrote: foilholio and kitexpert, you both seem to have lots of free time. Rather than arguing with each other, would each of you please take the time to write up a fool-proof, step by step and complete foil kite tuning/troubleshooting tutorial?
I have written so much already, here and elsewhere :-) Many may not be aware but much of what they form their basis of kite tuning, is from stuff I have already written. My writing style is maybe not clear and diverges a lot, particularly into banter with the local "expert" lol. Even he uses my old stuff but hey, it is funny. I will consider doing a tutorial I guess at some stage. If you search you will see I have started topics on many different things already.
sabraxas wrote: Kite expert and foilholio, can you explain how camber of profile is changed when aoa and lower skin área changed lineally?
If you are talking about mixer ratio matching bridle attachment lineally? Well it shouldn't with a regular bar, except the area between bridle attachments on the lower skin can get an increase in camber and the area after Z can lower camber. It is all to do with how the air interacts with the kite surfaces. Notably LEIs have this same effect, they tend towards higher camber as wind gives curve to the canopy. Which would explain their power and poor L/D. There is also alignment of the bridles or mixer settings which can be such that they pull a different camber than was sewn into the kite. Most foils though don't align bridles to match with mixer ratio so then their camber continuously increases. Extreme example is the A15, were the B ratio at 25% pulls at nearly half it's placement near 50% cord.
sabraxas wrote:And how arc and projected área of Foil Kite is changed?
First a kite gets shape from it's structure and how that structure interacts with the airflow.

Arc is changed by pull on parts of the kite to make it change it's shape. They can be either through the shape of the airfoil, or shape of the span. The tricky bit it would seem is how to make a kite actively do this. You can simply change bridle span to give a new arc. This would need to be on A to be most effective, but would need addition bridles there at most, or minimum of addition pulleys and attachments at the mixer. Now consider bridle attachments A B C and Z don't need to be the same across the kite. B could take a more A position , C could be more B and Z more C. Now also consider, a kite with the same A bridles quite flat, could take a very different shape with some small changes to it's sewn shape, particularly the AoA and camber on it's tips and A placement to reduce AoA. Now if we also know that the mixer can change camber and AOA. We have some possibility to change the shape of the kite. Through the airfoil shape, by changing camber, but also the span shape with bridle placement and shape. The biggest problem with that approach is the flatness comes with AOA increase. Fine in higher wind, where higher AOA won't stall a kite but in Low wind it will. And that is what happens with the Pyscho4, the low end is stuffed because it just stalls before it gets a good PA. Now that does not mean it is not a good concept, it is an excellent one. The range on a Pyscho4 is massive. Disabling the tips and the C shape is a fantastic way to have a very stable foil with high depower. The top end gained on a Pyscho4 well overcomes any lost low end for range. But for low end you need efficiency ( high L/D) and it can not achieve the low AOA with high PA to do that. That all said the concept still holds much promise but is seemingly very hard to design for. Flysurfer only ever released 2 sizes of a Psycho 5 (aka speed4 deluxe). The concept as flysurfer has implemented it is plagued with problems. The kites seem quite sensitive to manufacturing or age errors or deviations.

So that is my understanding so far :-) I am not an expert, but I know some things.

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Re: Foil Kite tuning tips

Postby sabraxas » Tue Jul 17, 2018 12:58 pm

Thanks Foilholio!

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Re: Foil Kite tuning tips

Postby twig » Thu Feb 07, 2019 10:09 pm

haare wrote:
Thu Jul 12, 2018 10:15 am
I Think that you can fix most problems with the first 2 videos. However if your kite still handles poorly you need to check the whole bridle. I made a short video of this. Sorry about the poor quality and bad english.
https://youtu.be/93Te2HGlXwY
Thanks for this great information! I saw your video and have some questions below.

Im surprised I have not found more precise and detailed information around how to trim foilkites to get back max performance. Maybe racers(people with most experince) want to keep their knowledge a secret to keep an edge against each other?

I have a used flysurfer and I would like to try your long way of fixing it, but have not started yet, it seems like alot of work.

I also saw your other videos on youtube on how you do the half knots to shorten the bridlelines closest to the kite at the connection points.
I was wondering if maybe the half knots reduce the strength of the bridle? Is this a common thing to do among foilkiters?

And another thing is, when two bridles meet they form a V, and that V has a certain angle pointing away from the kite, could it be that this angle changes a bit when you start to shorten all the bridles close to the canopy, and that you by accident make the kite out of tune/ worse than before? I guess that it will turn out great if im just careful enough.



What would be the best way to shorten a bridle that is between other bridles? Normal knots would weaken the line.

I have tried and successfully spliced some liroos dc60(thinner then normal kiteline) speed4 lotus line, and it was really hard.
Do you know where you could order alot of the liroos bridle type of line, same used for the flysurfer sonics? Have you spliced this and any tips for the splicing technique/ tools?
The first brummel lock is easy but then its really hard to get the end inside of the main line - thats my worry with this thin line.

alot of questions there but Im eager to get into it and learn alot more about foilkites. they are fantastic but yet so complex.

Thanks!

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Re: Foil Kite tuning tips

Postby kitexpert » Fri Feb 08, 2019 1:00 am

There's a bit too much calculation in haare's video. His english is pretty good though.

Best fix is to restore everything back to original lengths. Working order is: 1)flying lines 2)pulley lines/mixer 3)longest bridle lines 4)rest of the bridle lines.

Because practically everything which changes in length is from shrinkage remedy is to stretch lines back to original. Longer the line, more it can shrink. With a helper it is not that horrible job, both having screwdrivers which are put in the loops and then pulled it goes pretty fast. Line shrink is easily felt because line gives up and then becomes stiff under pull.

If every line is pulled kite will be better without any measurements. But of course it is reasonable to measure some lines here and there and compare lengths in the line plan. If there is considerable differences measure more. And it is also worth it to measure how stretching affects.

V-angles of the bridle lines are not that critical. FS uses quite long lines and angles are conservative.

Usually there is no need to shorten any lines because they are too short already.

Splicing can be done with a piece of thin steel line, copper line will do also. It needs some practice if line is very thin.

Racers tune their kites for the different conditions. It is not necessary for normal user with non race kites or even with race kites.

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Re: Foil Kite tuning tips

Postby SaulOhio » Sat Dec 14, 2019 8:52 pm

kitexpert wrote:
Fri Feb 08, 2019 1:00 am
There's a bit too much calculation in haare's video. His english is pretty good though.

Best fix is to restore everything back to original lengths. Working order is: 1)flying lines 2)pulley lines/mixer 3)longest bridle lines 4)rest of the bridle lines.

Because practically everything which changes in length is from shrinkage remedy is to stretch lines back to original. Longer the line, more it can shrink. With a helper it is not that horrible job, both having screwdrivers which are put in the loops and then pulled it goes pretty fast. Line shrink is easily felt because line gives up and then becomes stiff under pull.

If every line is pulled kite will be better without any measurements. But of course it is reasonable to measure some lines here and there and compare lengths in the line plan. If there is considerable differences measure more. And it is also worth it to measure how stretching affects.

V-angles of the bridle lines are not that critical. FS uses quite long lines and angles are conservative.

Usually there is no need to shorten any lines because they are too short already.

Splicing can be done with a piece of thin steel line, copper line will do also. It needs some practice if line is very thin.

Racers tune their kites for the different conditions. It is not necessary for normal user with non race kites or even with race kites.
I have a quiver of Ozone R1's and the bridles seem to be about 15mm short. Will getting them wet, then pulling them to their correct length, and letting them dry under tension work? I'm thinking of building a rack to do just that.

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Re: Foil Kite tuning tips

Postby kitexpert » Sat Dec 14, 2019 9:14 pm

SaulOhio wrote:
Sat Dec 14, 2019 8:52 pm

I have a quiver of Ozone R1's and the bridles seem to be about 15mm short. Will getting them wet, then pulling them to their correct length, and letting them dry under tension work? I'm thinking of building a rack to do just that.
I haven't thought that. Lines are PE which is immune to almost anything so wetting them probably doesn't help. Keeping lines under tension should give good stretching results but I haven't tested it either.

The more you load lines faster they go back to original lengths. I've never snapped a line when stretching, when you do it manually you feel how line reacts.

Perhaps best and easiest is just to start stretching them and then see and feel and measure what happens. Find out where most shrinkage is and work systematically, it can only get better then.

Stretching or final part of it is good to make in pairs, so taking same line from the both sides of kite. Then symmetry is remained.
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Re: Foil Kite tuning tips

Postby edt » Sat Dec 14, 2019 10:07 pm

haare wrote:
Thu Jul 12, 2018 10:15 am

1) Tuning mixer. Legendary video made by Armin himself. He also explains the profile changes quite well here
https://vimeo.com/9488886
This is great. Somehow the more you understand about a subject the simpler your explanations get. When you don't really know what is going on, that's when it all seems incredibly complicated. I remember the legendary richard feynman said once that if he couldn't explain it to his grandmother then he really didn't understand the subject yet.

2) Gunnars very good video about fixing kites by measuring bridle. This video was hugely important for me and has helped me a lot with my tuning troubles.
https://www.youtube.com/watch?v=C5twzrtvTP4
Good demo about how to fix your mixer length. I would just pull the lines to stretch them but what do I know.

3) Flysurfer soul designer talk. Explains quite well the different tuning options of flysurfer kites. PMAs etc.
https://www.youtube.com/watch?v=5grUtFc63GY&t=1596s
over an hour long I've never managed to watch this entire video, really slow pace, needs an edit. I get the feeling there's about 5 minutes of good stuff in this movie length video.
4) Russian foil expert extending D/Z line to improve kite performance.
Armin's video is better I think. This one would be way better if he got out a whiteboard and diagrammed what he's doing because not everyone knows what the "D" line is. The best part of this video is watching how a kite looks when it's unstable because the pulley lines shrank.
5) Kitetech video of tuning mixer
more mixer tuning, I guess the kitetech stuff is same as the "pro tune" stuff flysurfer has? For that system you don't need a complicated table the mixers are all same length. So easy to fix. The soul has this system too of course.

6) Flysurfer short video of mixertest


7) Ozone mixer test for protune system
https://ozonekites.com/videos/play/pro- ... eed-system
yet more mixer stuff.


For most kiters I would recommend just watching that Armin video twice or three times the rest of them you can skip. There's a lot of great info in that soul video but way too long. Thanks for grabbing these videos. I'm not sure really what kind of video the kite world really needs, all I know is if you want to make a video about foils please 1) keep it short. It's ok to shoot two hours of video but then use your editing tool and cut out the blah blah blah and get it under 10 minutes 2) use diagrams in addition to videos of the bridles. In real life the bridles just look like spaghetti, you need diagrams to simplify them so it's easier to understand.


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