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Tuning kite to correct flying issues

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davesails7
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Tuning kite to correct flying issues

Postby davesails7 » Wed Nov 18, 2015 6:23 pm

I don't think there was an overall tuning topic so figured I'd start one.

All 3 of my Sonics eventually started pulling slightly to the left after 20-30 sessions. I corrected this by shortening the C mixer between 0.5 and 1 cm on the right side of the kite. This worked perfectly for me. Is this the typical fix for a kite pulling to one side?

Also, what is the typical mixer adjustment to stop tip collapses?

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Re: Tuning kite to correct flying issues

Postby foilonfoil » Wed Nov 18, 2015 6:46 pm

1. Since all three kites, standard bar line check to make sure your lines are equal length at full power. I'm using the second knot on my bar rear lines so my rear lines are a couple of inches longer than my front lines.

2. Standard mixer test then compare length of each side of the kite bridle lines against each other.

3. I would also make sure nothing is out of place with the mixer itself as loops associated with the blocks may have moved.

4. Keep an eye on your kite tabs. I had one tab lose internal switching but it was a simple repair by accessing the back side of the tab via the edge vent.

5. Keep a close eye on the br-main lines and all the other yellow lines. I had a three flying line failure and the shock also broke the rear bridle lines. On replacement, I also found the rear bridle lines had sliced through the outer sheath of the br-main lines.

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Re: Tuning kite to correct flying issues

Postby foilholio » Thu Nov 19, 2015 5:02 am

I'll repost what I just posted in another thread.

The adjustment of mixers usually revolves around an even setting. Where all the bridles from the kite meet the mixer and all match each other at some combination of front and rear line adjustment.

The mixer is designed to depower the kite, achieve a flight profile and relaunch or reverse flight. If it doesn't do any of these there is something well wrong with it. All of these characteristics can be altered with how the mixer is adjusted. Of particular importance is the flight profile. A lower camber or negative camber will be more stable and have lighter bar pressure. A higher positive camber will have more lift, drag, less stable and with higher bar pressure. A neutral camber or profile will have the best Lift to Drag ratio, and will go upwind easiest. Profiles that radically pull on BC or Z and leave slack in the others will fly poorly. In all of my kites the progression of tension is B C then Z. They engage relatively close to each other with Z engaging just before the wing will stall or reverse fly.

Z is of most importance. As it usually only receives very light duty and tension, it will shrink the most. If it has shrunk a lot you can see the trailing edge of the kite becomes kinked a lot, the kite will also be unstable, tips collapsing etc with higher bar pressure. Lengthening it will resolve a lot of kite problems.

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Re: Tuning kite to correct flying issues

Postby foilholio » Thu Nov 19, 2015 5:29 am

Kite flying to one side, is asymmetry in front lines, mixer, bridles or canopy. To correct it you address them in that order till the problem is tolerable or fixed.

Front lines. I have had a number of uneven lines that can only be explained as having been made that way. To adjust lines you first need to take any shrink out of them. Applying a large even force to each line seems to work well. You can connect both lines in a chain so you can use your full body weight and the force is even. A small rope run through a pulley with 2 lines connected to each end of the rope, the other ends to something solid and even, will allow you to apply even tension at different lengths. Sharpie marks made at the same point/s on each line close to the pulley end, this can be used as a guide to adjust the lines later inside.

Mixer. With the mixer locked together at the front line attachments. Check for asymmetry and adjust or stretch out. Once even continue high up the bridles.

Canopy from foilzone
http://www.foilzone.com/phpbb3/viewtopi ... =1&t=18016

Great article written by Peter Lynn explains it http://www.peterlynnhimself.com/Pilot_Tuning.php. The bit to focus on is the sewing at the end. The diagrams dont match the explanation. Assuming the front lines and A bridles match, and the A tow points match, proceed to sew.

How I did it. Starting at the opposite side/end cell the kite turns to. At each cell line on the top skin fold the kite in half. I used one hand to hold the leading and trailing edge at their extremes. I then placed a finger in the middle to find the center of the cell wall. Use a pen that will soak through the cell and place a dot on the top skin near cell wall. Do this for a few cells in succession, the more the worse the turning problem. Hunt down the dots inside the kite through the the cell holes. Starting at the end cell. Sew a one ripstop square width pleat in the top skin,from cell wall to cell wall. Leave a 2 cm relief on each end, i.e. sew a diagonal on each end of the pleat so the pleat doesn't start straight at the cell walls but gradually. Use the ripstop squares as a guide to sew an even straight line. Do this to a few cells and subtract or add more later or one at a time. If the kite is unflyable you'll need about 6.

There is other possibilities of doing bigger pleats, pleats at other places than 50% and multiple pleats per cell. I would guess changes to the end cell/s have the biggest effect. This will also make the kite more stable. If applied to both sides it would reduce or stop tip flap, depending on the amount done.
Last edited by foilholio on Sat Jun 11, 2016 10:32 am, edited 2 times in total.

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Re: Tuning kite to correct flying issues

Postby holden » Thu Nov 19, 2015 9:50 am

@davesails7: i agree that before changing the bridle/mixer to correct behaviour, it is a good idea to check for asymmetry in flyinglines, mixer, bridles and canopy first.

one more thing:
if they pull to one side when fully depowered, you need to change B instead of C.

tip collapses are most likely due to too less aoa at the tips. shorter B at the mixer could help, or to make the As at the tips longer.

h.

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Re: Tuning kite to correct flying issues

Postby foilholio » Thu Nov 19, 2015 11:00 am

Most modern foils depower fully onto A and as such B changes dont really work.

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Re: Tuning kite to correct flying issues

Postby Johhnn » Thu Nov 19, 2015 3:43 pm

I've got an old Speed 3 deluxe 12 m that has a front stall problem. The last time I rode it, more than a year ago now, the left side near the center of the kite would fold over towards me. It happened several times and I could recover by reaching up and pulling hard on the right side steering line. Since I was in a safe area, a lagoon behind a breakwater, I continued to kite this way for awhile. I probably had 4-5 collapses like this. They were very intermittent and only happened during gusts. The mixer is properly adjusted.

Is this too high an angle of attack causing a stall?

Or is it too low an angle of attack, allowing the wind to get "on top of the kite" during a gust/wind shift? With all the suggestions of lines shrinking, I expect this is the case. I.e. that the bridle lines towards the leading edge are too short.

I also have backstall, but that seems like a separate problem.

I'm hoping to go through the bridle lines and carefully measure them and adjust as a winter project. I now have a Lotus 12 m. If I can get the old one working reliably, it'll take some of the pressure off the new one.

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davesails7
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Re: Tuning kite to correct flying issues

Postby davesails7 » Thu Nov 19, 2015 7:50 pm

Thanks! That's a lot of information to digest, will need to read through this some more.

For my kites pulling to the left, it was definitely the kites, not the bar because I use the same bar for multiple kites, and the pull was happening one kite at a time. I had checked the mixers first and all four knots were within a range of about 0.5 cm, so nothing noticeably out. I think I must have stretched the bridles unevenly because I loop the kite a lot more to the left than to the right.

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Re: Tuning kite to correct flying issues

Postby plummet » Thu Nov 19, 2015 8:26 pm

Start looping to the right then?

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Re: Tuning kite to correct flying issues

Postby foilholio » Thu Nov 19, 2015 10:51 pm

Take it in steps. You checked the lines.....please do, you checked the mixer, now check bridles. Remember this is not a mixer test although that can work.

Also I forgot . Check the C SPL are the same length. If they are a different length one side will depower more than the other. You tie the front line ELCs together to check for that. Actually to check for asymmetry, it's best to just tie the front lines together and check the mixer like that. Sorry I edited the other post. The way the mixer adjusts the kite it wont account for an imbalance in the C pulley lines. If one pulley line becomes 1 inch shorter then the mixer will only adjust half that out. It means when the kite is fully depowered, one side will be half an inch longer/shorter.


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