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Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

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Andeha
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Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

Postby Andeha » Mon Apr 20, 2020 8:45 pm

Hi!
I stumbled upon a good deal for a Sonic 2 that according to the previous owner wasn't preforming as new anymore. He had tried tuning it but had given up on it and decided to sell it as a project. I'm fairly new to kiting and thought this would be an excellent opportunity to learn how these monstrosities work. I watched several videos about trimming FS-kites before purchasing, and the fact that line plans are available made me go through with the deal.

The previous owner told me the following: "Suddenly collapsing in stronger wind. And unable to hold its shape unless the bar is close to fully powered."

So I started checking the bridle first, previous owner had added pig-tails that had dimensions way off according to the line plan. There was a lot of shrinkage in the bridle lines. But as I've understood, shrinkage is normal and can be compensated with correctly measured pig-tails.

I replaced and corrected all the pig-tails on the right side of the kite and took it out for a go.

My experience was the following: When the right side was pointing downwards, the kite would fly nicely(00:20). When the left side was pointing downwards(the one i didn't correct or alter in any way) the kite and wingtips would collapse and stall. (See beginning of video attached below).

My hypothesis is that this is because the pig-tails on the left side probably also has dimensions way off. I'm open for suggestions.

Footage of issues:

(Unfortunately I had my gopro settings to Medium-frame and not Wide, so its not always possible to see the bar position.)

So, let's say I fix the bridle issue and correct the lengths of br,c,b and a lines.

On to the next problem: The bar has to be close to fully powered for the kite to maintain its correct shape(02:20). However that gives me about 20 cm to go before the bar is fully powered. When I pulled it fully down, the kite would backstall. So I thought this had something to do with the mixer. I did a mixertest and the result was a mess. Z line too short, and C and B also off. Some of the pulley-lines had been replaced, other lines of the mixer had not. So, given the low price I've paid for it, I ordered replacement lines from FS and intend to rebuild the mixer. The pulleys themselves also had some play, so I ordered replacement of those too.

So my question to you experienced people out there, have I approached this correctly?
Any tips/advice/previous experiences and smart ideas is greatly appreciated.


Edit: My bar also probably needs some adjustments too, but I have not had any problems with it previously. Anyway, I guess it all adds up. :)

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Re: Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

Postby joriws » Tue Apr 21, 2020 10:13 am

Andeha wrote:
Mon Apr 20, 2020 8:45 pm
Any tips/advice/previous experiences and smart ideas is greatly appreciated.
To give tips what you could do and how. I attached the video for Sonic2, I don't know if video author Jussi is KF member so not sure if you can ask more here, but use Youtube comment or FB to contact him. And explain principles also in here as text.

You could start looking also "long mixer test" (LMT) videos released by Flysurfer. I think Sonic2 is not built/designed for LMT as directly doing what they are doing on instruction video but it does not matter as that just explains the process how to compare relative line lengths. So Jussi's video and FS video of LMT are same principles but for Sonic2 it is more work.

Download the line plan and use spreadsheet to calculate total designed length from mixer upper part to kite LCL (load fuse). Now compare relative lengths of a1 to a2 etc, so if line plan difference should be 15mm, now you can measure relative difference easily with short ruler, just remember to load the bridle with 5kg or more. This way you have relative measurements about bridle shrink, and if you want you can start adjusting that by doing additional loops to LCL by shortening bridle. Sure you can add additional LCL to top of previous LCL to lenghten etc. But plan a bit what is the best way forward, least modification for less work. I think I can recall that 5mm difference from "optimum" bridle lenght is not worth adjusting, maybe it was 10mm. I think I heard that from Flysurfer / Armin video about LMT, so you should definetly check the videos too.

If this still fails to fix the kite, you could think of PMA adjusting of wing tips to counter fabric changes. You should check PMA videos from Flysurfer. But most likely relative bridle fixing will fix your kite.


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Re: Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

Postby Adventure Logs » Tue Apr 21, 2020 11:06 am

No PMAs or long mixer test on the Sonic2. It seems like you are willing to put in the work. What I would do...first bar test. Trimmed for full power, with bar fully sheeted in, all lines should be equal. Next mixer test, I bet she will backstall like a bitch and you’ll need to extend Z. If you get rid of the backstall but the wing tips are still collapsing/kite is tacoing, you can shorten b and c.

Also you can measure out each bridle line and try to restretch the lines. Also wouldn’t hurt to inspect the inside through the intakes to see if there’s any internal damage.

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Re: Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

Postby joriws » Tue Apr 21, 2020 12:08 pm

Adventure Logs wrote:
Tue Apr 21, 2020 11:06 am
No PMAs or long mixer test on the Sonic2. It seems like you are willing to put in the work. What I would do...first bar test. Trimmed for full power, with bar fully sheeted in, all lines should be equal. Next mixer test, I bet she will backstall like a bitch and you’ll need to extend Z. If you get rid of the backstall but the wing tips are still collapsing/kite is tacoing, you can shorten b and c.
Normal mixer tests etc, I already assumed these have been done dozen times by previous owner and by OP's text also by current owner, sure bar tip to trim lines even is todo task on long list of resetting everything to factory spec. That's why I started giving tips beyond "mixer test" if wing tips are loose/collapsing, uneven loading of bridle compared a1 to a12 might have uneven shrinkage and caused AoA change on wing tips, and also a1 relative to b1 and c1 changes behaviour. I though going bridle over relative each other is new thing to be done to the this kite instead of building all bridle from ground up what I understood from OP.

Like I stated "LMT on Soul" is relative bridle test on Sonic with line plan calcs. So "LMT" exists on Sonic and on every foil kite where line plan is available. Maybe it should be called RBM (relative bridle measurement). If mixer on full power (front-back lines equal) should have ABCZ equal, that could be used as zero point for RBM too. That's why I suggested measuring above mixer the relative bridle lenght and adjusting if there are large deviations to factory spec. And you could easily attach water bucket via pulley to above of mixer. That water bucket could be even used to stretch the briddle but I've understood stretching is not final fix, might work for 10h but...

About PMA, I though they are in all "recent" kites of FS, starting from Speed4DLX mark 2. I've never checked in my own Sonic2 kite but made the assumption. So PMA might not be an option, and it should not be first option to fix the kite. First he should work with canopy curve / camber / AoA.

You could also check gmb13's video of "short RBM" but he's fixing on assumption that a-b-c has shrunk contant rate also from left-to-right (a1->a12, b1->b12 etc). Could be true but I suspect you should measure uneven shrink also left to right:

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Re: Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

Postby Andeha » Tue Apr 21, 2020 12:38 pm

Thanks for the knowledgeful responses! Yeah I'm down for putting the work in. I dont charge myself much per hour ;) +added benefit of learning something new.

Internaly the kite looks ok. Tried pumping it up with air, also checked each cell wall. Luckily no problems there.

Yeah I dont really believe much in restretching. Ive ordered new lines for the mixer.

I think ive seen all of Armins videos, i must have missed the one about LMT. Will check it out.

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Re: Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

Postby darippah » Tue Apr 21, 2020 1:17 pm

I had the same exact issue with my 13m Sonic 2. Mixer was slightly off but did not help to adjust. I was on a Kite Vacation and someone on the beach recommended adjusting the PMA's- that solved the problem and I don't notice a negative affect.

My 11m had the same issue . Adjusting PMA's helped here as well.

I recommend to try this for anyone looking for the easy way out, and willing to (possibly) sacrifice some performance.

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Re: Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

Postby Andeha » Sun Apr 26, 2020 6:03 pm

Okey, so I am starting to see light at the end of the tunnel for this project! Tested it today, in 10-15knots, and what a superb kite the Sonic2 is, can really feel the potential of this kite. Having corrected most of the bridle its a whole lot better, though i need to correct the right side some more. However I am still waiting on replacement lines for the mixer from FS, hopefully this will fix the remaining problems.

Where would I find the PMA adjustments on Sonic2? Same position as on the Soul?
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Re: Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

Postby Carlos_C » Mon Apr 27, 2020 12:30 pm

I had an issue - once with the my Sonic 2 - would not inflate - wing tips kept collapsing - re did the mixer - even though it was not off - and since then has been perfect - for me at approx 70 kg the 13 is the biggest kite I will need for a twin tip

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Re: Help re-tuning a Sonic 2, am I on the correct path? Bridle/mixer

Postby kiteexpertyexpert » Tue May 12, 2020 10:19 pm

The number one way to tune any foil kite is adjust Z


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