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DIY Foil Kites

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Schietwedder
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Re: DIY Foil Kites

Postby Schietwedder » Sat Jan 02, 2021 11:52 pm

Hi Rein, Nice! Then we will see it in the air quite soon? Am really interested how it works out with the higher AR. I might as well be tempted to try some higher AR kites in the future.

I ordered directly at Liros as I am sort of a retailer with my small sailmaking loft. I can send you some lines.
I am short of DSL lines though at the moment but there is a good online shop in Germany called Metropolis Drachen where you can get the covered DSL by the meter which is less likely to get out of tune and faster to assemble as you just sew it together to the direct specification and not splice where you also have to account for shortening of the line because of the splice. It took me twice as long for a spliced bridle this time around although it is a bit more neat and less prone to tangles of course.

I run a flysurfer spec mixer before I was on the ozone adjustable for R1 but it is a bit shorter and the Flysurfer works better, don't ask me why :p But as you are using the same profile like me maybe you should take the Flysurfer spec mixer.

I have some sort of pigtails between the kite bridles and the mixer as shown in the sketch. You could also as well use an adjustable mixer but then you don't know if your mixer is at zero or what adjustments you run with the kite. I found this particularly practical as I use the pigtails for two purposes.

1. You can only guess what the towpoint (% of chord) will be like in flight. (Initial AoA) The problem with that is if you find your initial angle of attack of the kite too small or to big for the kite fully depowered, you can adjust your lines with the bar trim or steering line knot ladders at the bar below the mixer of course which seems quite straightforward in the first place but you will fully destroy your profile if unlucky. The mixer motion is not linear. Meaning that if you pull the bar from mixer set at ABCD level (zero) it doesn't only change the AoA of the kite but also cambers the profile more. (Or reflexes it more when the bar is let out more) So Z is not adjusted linearly in relation to ABC and so on.

So you want to adjust the initial towpoint or the sweet spot of the kite when powered/depowered ABOVE the mixer in linear preset (+/- 1cm at B, 2cm at C; 3cm at Z or a multiple of that )

2. Then if that is found you can start play with the other levels like reflex/camber etc, but the profile works of course best if you don't have to adjust much which should be the case for a well designed kite.

Also your towpoint in front view (%of span) have to be according to the linelength of your bar.
So you will be running the load on all areas of the kite equally and to not disturb the shape of the canopy in the air.
You can set the linelength in Surfplan in the "Advanced" Menu, and also put the towpoint on Auto in the bridle menu. Then if really advanced you can account for different lift coefficients because the centre usually runs a profile with higher lift(more camber) than the tip profiles (more reflex).
It means that the centre needs also a bit more support than the tips of course by the bridle geometry as the angles in the lines determine how the loads are transmitted and splitted
You can account for that also in the "advanced" menu by using different lift coefficients by feel or by CFD analysis of the profiles for example in XFLR 5 under realistic reynolds numbers.
(In CFD it's problematic to determine realistic absolute values as a beginner but relative values (compare two profiles in a batch analysis) are quite accurate usually)

Have fun!
Last edited by Schietwedder on Sat Jan 02, 2021 11:59 pm, edited 1 time in total.
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Rein de Vries (Thu Jan 07, 2021 10:49 pm)
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Schietwedder
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Re: DIY Foil Kites

Postby Schietwedder » Sat Jan 02, 2021 11:55 pm

Sketch
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Screenshot_20210102-235407.png
These users thanked the author Schietwedder for the post:
Rein de Vries (Thu Jan 07, 2021 10:48 pm)
Rating: 6.67%

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Schietwedder
Medium Poster
Posts: 56
Joined: Sun Dec 09, 2018 1:35 pm
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Has thanked: 9 times
Been thanked: 23 times

Re: DIY Foil Kites

Postby Schietwedder » Tue Jan 12, 2021 10:59 pm

Continuing at the tips
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