Contact   Imprint   Advertising   Guidelines

Foil Kite tuning tips

For all foil kite riders


kitexpert
Very Frequent Poster
Posts: 503
Joined: Sun Aug 09, 2015 11:20 pm
Kiting since: 2003
Gear: many kites, also diy
Brand Affiliation: None

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.

User avatar
sabraxas
Frequent Poster
Posts: 257
Joined: Fri Nov 19, 2004 11:40 am

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.

kitexpert
Very Frequent Poster
Posts: 503
Joined: Sun Aug 09, 2015 11:20 pm
Kiting since: 2003
Gear: many kites, also diy
Brand Affiliation: None

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.

foilholio
Very Frequent Poster
Posts: 2203
Joined: Sun Aug 23, 2015 3:20 am
Kiting since: 1337
Local Beach: Ventura Beach
Favorite Beaches: Tarifa
Style: Airstyle
Gear: Foils
Brand Affiliation: None

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.

User avatar
sabraxas
Frequent Poster
Posts: 257
Joined: Fri Nov 19, 2004 11:40 am

Re: Foil Kite tuning tips

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

Thanks Foilholio!


Return to “Foil Kites”

Who is online

Users browsing this forum: No registered users and 4 guests

cron