Hi guys,
I am a new-ish user to foil kites and in desperate need of some help,
Issue: 2015 Flysurfer Sonic FR
When ever i sheet in the bar at all, the kite back stalls and looses all power. This issue wasn't as bad when i fully de-powered the kite - which shortens the center lines and respectively lengthens the real lines. (this suggests that my rear lines are too short, stalling the kite whenever i try and sheet in to gain more power)
To fix this issue, should i lengthen the rear lines - if so, by how much?
When my bar is fully sheeted out and depowered - the kite is fully powered. Any thing sheeted in or added power (lengthening center lines), the kite falls out the sky.
Please Help as i have missed many sessions because of this.
Thanks in advance guys. 
Line stretch / shrink is common to all kite's
Do some research on the net
Here are a few starting points
www.facebook.com/flysurferkiteboarding/photos/want-to-tune-your-flysurfer-kite-and-bring-it-back-to-its-maximum-performance-fa/849624655072556/
www.seabreeze.com.au/forums/Kitesurfing/General/Any-suggestions-on-tuning-Flysurfer-sonic-15-m?page=1
kiteforum.com/viewtopic.php?f=1&t=2374470
Assuming your bar is correctly calibrated... all lines equal length when fully sheeted in... the next thing is to start checking the bridles for irregularities such as stretch or incorrect assembly. If your bar is correct what you describe goes beyond bridle stretch and for me points more toward missing pieces or incorrect set up of the bridle system. You should be able to get detailed diagrams and measurements for your bridle from Flysurfer
First -- tune your lines, check your main depower line length (the one through the bar), and do a mixer test if you must, but don't touch anything else.
But ... it's not a tube kite -- so don't fly it like one.
Let the kite fly. Sheet in to milk a bit of power, do NOT go hauling on the bar expecting it to give more power the more you pull the bar. Just doesn't work that way.
I'm betting you got it for light wind, so you're probably muscling the bar too much like you would with an LEI, and choking the kite.
The original Sonic was a bit twitchy, and being a race kite it was a bit of a handful. They're high AR too so it doesn't take a lot of bar pressure or movement to choke them. The smaller the foil, the easier it is to do too.
Easy fix...
1.Make sure your depower is released.
2. Measure depower line (You said it reduces backstall)
3. Your depower line length + another 20cm - should be added to the 'Back Line's.
That 20cm length is measured after you tie figure 8 knots at 5cm intervals..
Get someone to launch / land your kite on the beach - until you find the correct knot that doesn't stall the kite...
Do this in at least 15 knots of wind.
Cut off any excess line once you find it.
Hi Camlakes,
you need to just check the lines for equal length, then do the mixer tuning as per the many you tube vids available.
STW is right, you need to leagg Ttf n how to fly foil kites, you don't generally sheet them in hard for more power. Let the "breathe" by easing the bar out a bit and letting the kite accelerate and create power through speed and apparent wind.
this should sort it out if you follow the instructions.
DM
As from my experience the front lines should be slightly longer, 3-5cm. ( i fly sonics, and this gives me better performance).Apart from that, totally agree with DM. Don't choke the kite.
Just play around and find what is working for you.
Best of luck.
The above advice is good. Equal line lengths, do a mixer test and get a,b;c,d's all even.
Then learn to not choke the kite and let it breath. You can trim the kite to little or no back stall like an lei. But then you lose the advantage of back stalling..... I quite often use the back stall feature on purpose to get the big lumbering foil to pivot turn quickly and shoot off in a different direction.
As foil kites get older its normal for the bridles to shorten (actually they are just losing their pre-stretch they had when new) and particularly levels B and C often shrink more than A (I think due to the pulleys in the mixer maybe?). What this means is that the B and C levels being shorter makes the kite more "stally" which is what you are describing. The best way to sort it out is the long mixer test which is in a few vids on youtube etc, here are two vids that I like: ttps://
and
and as others have said get your bar and lines "bar neutral". If you find that you want to lengthen B and C levels there are other vids on how to do that but essentially you can do it in the mixer either with adjustable knots/rings or if that option isn't there you can just add some small looped bits of line.
