Better depower and stability for 1$

Kitesurfing/Kiteboarding on Liquid H2O

Better depower and stability for 1$

Postby Andreas » October 22nd, 2013, 4:33 pm

Background:

I'm quite happy with my SYN15, but miss the massive depower I had in my unmodded VII16. The only thing I didn't like with the VII was it's tendensy to bowtie. But I think I have a soulution for that (a air tube or spar in the middle pocket, make the AR effectivly half), but didn't try it before i crashed it severely. Anyway, the Syn is not prone to bowtie, but I would like, in the upper range, have more depower without sacrifice stability, I'm ok to give away turning speed and low end grunt for that.


Testing:

I've read that shortening the middle strap make the arc more stable since it do the bottom skin bulge downward. Also this may do the kite pull less, in theory at least.

To shorten a strap I use a bit grind down press buckle (have no pic yet) the same width as the strap, fold the strap and put it through the buckle. This way I dont need to sew or cut anything.

So I begin to shorten the middle strap in the wintip inflate cells. I begin with something like 30 - 40 cm / 10 - 15" shorter on both sides. It looked really awkvard in flight, of course, but I couldn't notice any better depower, it was also luffing in the middle of the kite when depowerd. Soon the buckles couldn't hold the force so the strap slide to be somthing like 10 cm / 3" shorter at each side. Couldn't notice any benefit then eiter, the luffing persist but less strong, obviusly. I was disapointed.

I didn't think that shortening the middle strap in the center/deflate cell would do any difference since it's the same strap, but I forced myself to test it anyway. In the center cell the strap is sewn to the cell walls so I didn't dare to short it more than about 10 cm / 3".

Then I fly it and... Success! At first I thought the wind had really dropped but little by little I start to drive the kite deeper and faster through the window and the depower was really improved (actually it felt tremendous). And not only that, -it was unimaginable stable at zenith! I really provoked it in the gusty light wind, but it always stopped just before the edge nomatter what I did. I was concerned that this mod would make the kite stally, but I couldn't recognise any such tendensys. The power come on nicely when the bar was pulled in and steering was not affected.

Drawbacks:

I have only flied it a short time static, so I don't know for sure how it will behave when boarding. The middle cell looks strained, see pic, but the buckle is weak and didn't slip like when mounted in the wingtips, so the load may be low. Also if this buckle is used it may slip in flight and the power come on too much. The low end power is less but it feels I gained more in the high end than I lose in bottom. I think the kite is sitting a small bit further back in the window.


Conclusion:

Would I dare to say I have a Syn15 with the depower of a VII16 :?
Attachments
SMC - Copy.jpg
Shorter middle strap in center cell
SMC - Copy.jpg (27.97 KiB) Viewed 4286 times
C-QUAD 3.2, C-QUAD 4.2, ARC 1120, ARC 460, Waterfoil 3.6 (Now rep :-) ), Flysurfer MastAir 16, Vade Retro Satana 7 m2 (under rep), VenomII 16 (waiting for rep), Synergy 15.

Top speed on skies: 71,0 km/h or 44.1 mph (feb 24 -2011, Syn 15)
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Andreas
 
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Location: Gothenburg, Sweden

Re: Better depower and stability for 1$

Postby Andreas » October 31st, 2013, 2:32 pm

I've now measured, and the middle strap was shortened 12 cm / 5" in the center cell. I would recomend max 10 cm / 4" shorter for not strain the seams to much.

I have also take pics on the press buckle I use and how the strap is fed through it.
Attachments
DSC00535 - Copy.jpg
Press buckle
DSC00535 - Copy.jpg (58.51 KiB) Viewed 4212 times
DSC00537 - Copy.jpg
Strap fed through
DSC00537 - Copy.jpg (47.79 KiB) Viewed 4212 times
DSC00545 - Copy.jpg
View inside
DSC00545 - Copy.jpg (36.5 KiB) Viewed 4212 times
C-QUAD 3.2, C-QUAD 4.2, ARC 1120, ARC 460, Waterfoil 3.6 (Now rep :-) ), Flysurfer MastAir 16, Vade Retro Satana 7 m2 (under rep), VenomII 16 (waiting for rep), Synergy 15.

Top speed on skies: 71,0 km/h or 44.1 mph (feb 24 -2011, Syn 15)
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Andreas
 
Posts: 47
Joined: July 8th, 2010, 2:21 pm
Location: Gothenburg, Sweden

Re: Better depower and stability for 1$

Postby tungsten » November 1st, 2013, 7:51 am

If you want to shorten the braid by that amount, I would spread the mod over the 3 middle cells. Do not shorten more than 4cm in one cell, otherwise the seam will break. If it's like in your picture it won't hold long.

It is quite easy to reach the cell left and right of the middle cell by putting your finger through the hole in the rib where the 3rd (TE) braid goes through. pull the braid you want to fix through that hole, make your fix, and shove it back.

Those plastic adjusters are likely to not hold long as you load them perpendicular to their designed direction.
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Re: Better depower and stability for 1$

Postby Andreas » November 1st, 2013, 1:51 pm

Yes I thought about divide the shortening to the three middle cells but was hesitant to cut in the cell wall for reaching them. Didn't think one can get access through the third strap holes in the cell wall, -thanks :) One nice thing with this mod is that it is easy to remove in the lower wind range when it's not wanted. Maybe also 4 cm shorter is good enough.
C-QUAD 3.2, C-QUAD 4.2, ARC 1120, ARC 460, Waterfoil 3.6 (Now rep :-) ), Flysurfer MastAir 16, Vade Retro Satana 7 m2 (under rep), VenomII 16 (waiting for rep), Synergy 15.

Top speed on skies: 71,0 km/h or 44.1 mph (feb 24 -2011, Syn 15)
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Andreas
 
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Joined: July 8th, 2010, 2:21 pm
Location: Gothenburg, Sweden

Re: Better depower and stability for 1$

Postby tungsten » November 1st, 2013, 7:08 pm

It's never necessary to cut the cell wall (profile). Either you get in through an existing hole, or you unstitch the TE. That's quick and easy and does no harm to the kite.
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Re: Better depower and stability for 1$

Postby Andreas » November 4th, 2013, 2:43 pm

Good Point, taken and appreciated. The idea of cutting the cell wall was to allways have access to the nieghbor cells for activate and deactivate this mod. It's so hevy to bring the sewing machine to the beach :lol: Anyway, third strap hole hopefully work fine.
C-QUAD 3.2, C-QUAD 4.2, ARC 1120, ARC 460, Waterfoil 3.6 (Now rep :-) ), Flysurfer MastAir 16, Vade Retro Satana 7 m2 (under rep), VenomII 16 (waiting for rep), Synergy 15.

Top speed on skies: 71,0 km/h or 44.1 mph (feb 24 -2011, Syn 15)
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Andreas
 
Posts: 47
Joined: July 8th, 2010, 2:21 pm
Location: Gothenburg, Sweden

Re: Better depower and stability for 1$

Postby Andreas » September 29th, 2016, 2:53 pm

Sorry to dig up this old thread. I’m not progress very fast ;) And also the forum has been down a long time.

Anyway, I did cuts in the cell walls next to the center cell. So I easy can put the pressbuckles on all three centre cells (going through the third strap opening was too awkward outdoors for me). The forces on the cell wall is predominantly in bottom skin – top skin direction so I did fairly big cuts in this direction, without removing any fabric. The cell walls is now only weeker in LE – TE cord direction but don’t think this is any issue. Also I did not reinforce the cutting in any way by purpose to see if any rip will occur.

Test:
First I tried with 12 cm in each cell for 36 cm shortening total just so I could find the upper limit. This was too much as the air valves folded back so much it was not possible to inflate the kite enough to fly.
Next I tried with 6 cm in each cell for a total of 18 cm. I could fly but it felt a bit weird, vague feedback from the kite (thou the wind was terrible, weak and come from all directions including up and down). I also had problem with the buckles on either side of the center slipped.

Conclusion:
Upper limit is less than 18 cm shortening total. Probably 4 cm in the middle three cells is max recomended for now.
The pressbuckles is a very neat solution to short, adjust and put on and off the middle strap, but cannot hold suffient force (they have not break, but the strap slip). Need something better. A crude solution can be to do alpine knots on the strap?
The cuts in the cell wall was not affected after a few crashes. They also improves preinflating. See picture.
Attachments
Cutcut.jpg
Synergy 15
Cutcut.jpg (142.97 KiB) Viewed 2219 times
C-QUAD 3.2, C-QUAD 4.2, ARC 1120, ARC 460, Waterfoil 3.6 (Now rep :-) ), Flysurfer MastAir 16, Vade Retro Satana 7 m2 (under rep), VenomII 16 (waiting for rep), Synergy 15.

Top speed on skies: 71,0 km/h or 44.1 mph (feb 24 -2011, Syn 15)
User avatar
Andreas
 
Posts: 47
Joined: July 8th, 2010, 2:21 pm
Location: Gothenburg, Sweden


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