Tip curling - luffing or arc and cell pressure

[Jyoder]

All these guys with expert knowledge of foil kites and they keep their secrets about how to tune them so close to the vest. Share your knowledge guys!

No no no! we don’t need more obtuse endless circle jerk from foilholio clones vs kitexpert.

I do wish there was an easy drag and drop app that let you adjust and visualize a virtual mixer with different attachment locations and lengths, etc.

[Herman]

Trouble is the fun is in the riding and, actually, I think I have got what I needed in this thread to sort out my understanding (could be delusional). If I get serious about it I will make up a permanent 10m rig and get an old audio tape out to chop up into some telltales.

I think the laser measurement and data recording etc discussed in a previous thread may be the way to go if you want to win races but I am happy as long as a kite is fun to fly. Not sure there is actually any sound formal approach that is full proof, although somebody could write a book on it rather like the many sail trimming tomes that are available in all good book shops.

[flying grandpa]

IMHO the reason of tip collapse may origin in the differece of camber in center part v tip.
If the center have big camber it is slow and sits in the back of the wind window.
If the tip have small camber, it is fast and sits in front of wind window and thats why it is more prone to collapse.
To cure the problem make central part faster by flater camber and tips slower increasing their camber.
In Sonic3 - shorten upper PMA’s in the center
and at tips shorten lower PMA’s.
Fly safe
Tadeusz

[jakemoore]

In Sonic3 - shorten upper PMA’s in the center
and at tips shorten lower PMA’s.
Fly safe
Tadeusz

OPs problem is occurring with the bar sheeted in.

In my experience PMA have a greater effect in the kites behavior when the bar is out.

And shortening the PMA on the bottom skin at the wingtip would increase tip collapse?

It’s easy enough to change the PMA and recover the default setting that change so it’s a good idea to try.

[Herman]

Yep, always good to be reminded about your profile momentum adjustment so thanks for that. Change in camber has oft been discussed and as flying grandpa points out is bound to have an influence on this effect. The speed and drag of the tips could also be influenced by designed or unwanted twist, should be a doddle to sort out with all these parameters to choose from! Especially as the working centre of the bridle is not even a fixed point.

[flying grandpa]

In my experience PMA have a greater effect in the kites behavior when the bar is out.

I do not now the influence of these changes on overall kite performance, but they solved the problem of tip collapse permanently in my gusty lake conditions

[edt]

IMHO the reason of tip collapse may origin in the differece of camber in center part v tip.
If the center have big camber it is slow and sits in the back of the wind window.
If the tip have small camber, it is fast and sits in front of wind window and thats why it is more prone to collapse.
To cure the problem make central part faster by flater camber and tips slower increasing their camber.
In Sonic3 - shorten upper PMA’s in the center
and at tips shorten lower PMA’s.
Fly safe
Tadeusz

here's what I don't understand, why would the profile moment adjuster those internal things inside each cell have to be adjusted because a kite has aged? I know all the bridle lines (except for some of the the A risers) shorten over time and it makes some sort of sense to me that you would adjust both the mixer adjusters behind each pulley on the kite and also add pigtails to the wing to adjust for changes over time of the kite, but how would age affect the shape of the actual fabric? If you want to adjust the camber of a section of the wing, wouldn't it make more sense to add 2cm pigtails to the bridle lines attached to the kite near the end of the wing at B and C, leave the middle alone and this would create more camber at the tips and flatten the middle?

Thanks for any advice!

your explanation makes a lot of sense, you slow down the middle and speed up the wings, I just figured it was better/easier to do with little pigtails, but maybe PMA is how you do it? I don't remember pansh kites having those PMAs but maybe they have them.

[Herman]

The way I think of it is a bridle adjustment just changes the position of the bottom surface. The pma changes the shape of the rib. Sadly never had a Sonic.


PS pure conjecture on my part but, I am guessing, that pmas were put on a prototype rather than remake a rib to try a tweak, and found to work. Also are pmas just a Sonic thing or is the Soul and vmg fitted with them as well?

[flying grandpa]

here's what I don't understand, why would the profile moment adjuster those internal things inside each cell have to be adjusted because a kite has aged?

Main isue with older kites is inside preesure that decreases slowly with each session, as small holes from sewing incraese in size.

My understandig of my tip good work is, that faster middle/slower tips change the shape of the kite seen from above.
Front goes a bit ahead but tips go a bit back - and that tip movement increase tip AoA just enough, to solve tip collapse problem.
On the other hand, such a kite may have less boosting and will not go as close to the wind, but I take it as a cost of safety in gusty winds.

Tadeusz

[edt]

The way I think of it is a bridle adjustment just changes the position of the bottom surface. The pma changes the shape of the rib. Sadly never had a Sonic.


PS pure conjecture on my part but, I am guessing, that pmas were put on a prototype rather than remake a rib to try a tweak, and found to work. Also are pmas just a Sonic thing or is the Soul and vmg fitted with them as well?

I really liked what flying grandpa said a lot of insight into what happens when a foil kite ages. Herman try this:



you're basically shortening the "BI" line by adding some pigtails onto ACZ and just part of B. That I think will cause the B section right in the center of flatten, and change the angle of attack making the tips uncurl. The PMA stuff might work too but PMA is a PITA.