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DIY Foil Kites

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kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Thu Dec 20, 2018 8:45 pm

klimm wrote:
Wed Dec 19, 2018 3:51 pm
Laid flat, the LE is very curved at the ends. The TE is much flatter.
Ok, just try to get your model in SP as close as possible to same as your kite is. Then you will have as precise bridle as possible.
klimm wrote:
Wed Dec 19, 2018 3:51 pm
The picture in the lines plan, that you also have is not accurate and is laid flat anyway.
It is ok to be flat, it should be flat. I wouldn't doubt accuracy that much, it may be the best information of kite shape you will have.
klimm wrote:
Wed Dec 19, 2018 3:51 pm
I compared my design with the real thing laid on the floor. In the design, I tried with some approximation to get as close as possible to the projected shape.
Comparing is ok. You decide by yourself how projected shape will be, within those limits PG parts allow. Just try to make it look good, wing will take that shape without much problems (as far as you are not doing anything too extreme).
klimm wrote:
Wed Dec 19, 2018 3:51 pm
Concerning the lines, I think that only the first level could be used (about 50-60 cm) at all levels. A,B,C even some of those on the commands(brakes)

Of course you use original lines, but they are only raw material to new lines. Don't try to match your design to original lines, it makes no sense because your new wing is different and it is almost impossible task. You must make every line new line, your SP model is done exactly for that purpose, to give new bridle line lengths.
klimm wrote:
Wed Dec 19, 2018 3:51 pm
Of course I will try to use old lines where it will be appropriate, with a larks head at an end for adjustments.
By accident it is possible that some of your old lines will match new lines, but most of them (90-95% (?)) you must cut and make a loop in them according to your plan. Recycling old lines is easier than to use bulk line because ends have loops already, only one end have to be made. Simplest way to make new loops is by knots.
klimm wrote:
Wed Dec 19, 2018 3:51 pm
I still have some doubts with too short 2nd and 3rd level lines not to distort too much the canopy
In your design first and second level are much too long, third level is too short. Length from the canopy to the end of the bridle is not long at all, more like short. Towpoint separation is ok.

Your canopy curve is too much in the center, adjust it towards the tips (like 50% or more). Amount of curve is ok.

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Re: DIY Foil Kites

Postby revhed » Sat Jan 12, 2019 5:41 pm

Do you BRAVE D I Y Ram air kite builders :thumb: include L E form supports like FS soul and most Ozones?
I see that almost all paragliders employ these but makes sense as is open cell and you are flying! :o
I ask only because my ultra cheap but ok flying Aurora has none and is easy to see the L E being pushed into itself.
I have checked and seems not so time consuming to add a rounded L E stiffener in between cells at sewn seam.
Wondering what material to use if so and is it worth it?
Any and all info much appreciated! :D
Must say my DIY thin lite cut off from SUP paddle handle BAR is very light and stiff, works well!
R H

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Re: DIY Foil Kites

Postby Regis-de-giens » Sun Jan 13, 2019 11:07 am

You can use nylon strings from grass cutter rotating machines.
Image
On my custom singleskin i used tennis raquet strings which is even lighter. That seems a bit weak at first sight but since the string will be locked along the intercell cloth (i.e. deformation is in one plane only), it is stiff enough (and un-breakable).

I sewed nothing and just inserted the string in the existing intercell sew.

But IMO Aurora does not need this and you may induce premature wear.

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Re: DIY Foil Kites

Postby Schietwedder » Fri May 08, 2020 2:49 pm

My latest 12m design
AR 5.2
36 Cells
Skytex 40
Glass fiber epoxy 0.8mm leading edge battens
One 3d shaping seam in Upper LE
3-5% billow
5 vents
Internal straps
Bridle every 2 ribs
No diagonals

Bridling and then see how it goes
Attachments
IMG-20200508-WA0007.jpeg
IMG-20200508-WA0009.jpeg
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kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Fri May 08, 2020 4:08 pm

:thumb: Very pleased to see that, it looks good. What I can see from airfoil shape, kite shape and canopy curve they look good as well.

Bridle in every second cell is proven solution and because it doesn't need diagonals (necessary) it makes kite relatively simple and also light weight.

One possible bridle configuration:

Image

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Re: DIY Foil Kites

Postby Rein de Vries » Sat May 09, 2020 9:54 pm

Very nice to see, looks professional even!

Also nice this thread is alive again, was just reading through it these days in my diy learning process. Thinking about my next project in Surfplan and seeing your 12 makes me wonder. How do you introduce the 3-5% billow? Is it a manual thing you add to the cell width, tapering off to the edges. Surfplan has a skin tension parameter I see, which might be used for it, but I am not so sure.

I am also very much interested in your rule for the strap tension. Does it relate to the billow parameter somehow? On the commercial models it seems to be sewed in like that.

Thanks kitexpert for the bridle picture, it helps me with a decent canopy as well!

Looking forward to some surfing pictures on that 12! 👌

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Re: DIY Foil Kites

Postby Jyoder » Sat May 09, 2020 11:43 pm

What if you made a foil kite bridle and bar setup with only a single center front line instead of two? Would there be a benefit in bridle simplicity? What would be the best way to setup a speed system that goes from one front line to two back lines I wonder?

No flag out safety of course, but I haven’t ever flagged a foil kite anyway.

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Re: DIY Foil Kites

Postby kitexpert » Sun May 10, 2020 12:20 pm

Jyoder wrote:
Sat May 09, 2020 11:43 pm
What if you made a foil kite bridle and bar setup with only a single center front line instead of two? Would there be a benefit in bridle simplicity? What would be the best way to setup a speed system that goes from one front line to two back lines I wonder?

No flag out safety of course, but I haven’t ever flagged a foil kite anyway.
Speed system is a problem if there is only one flying line, so possible gain in simplicity is lost there. High Y setup is however possible, I had it for years in my big foil kite. FS used to have it also. But I don't know if there is much benefit and single front line flagging is not possible of course.

Schietwedder
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Re: DIY Foil Kites

Postby Schietwedder » Mon May 11, 2020 2:31 pm

Hello back and thanks for the comments.

As to how I did the billow/strap tension:

I designed the kite in Surfplan and Foilmaker, as both have quite similar settings for the basic kite shape.
As I had a sailmaker friend with a Lasercutter, I did the final export as a .dxf export in foilmaker, because Surfplan didn´t let me to.
So i had cells, upper skin (which I later cut for 3d shaping) and lower skin incl. basic skin tension cut out.

For the custom parts, like vents, 3d shaping in the upper panels and straps (incl. tension and taper) which is quite hard to get as i wanted it to look like from both programs (Surfplan is better though)
I did a lot of manual but practical old school work with paper patterns, excel calculations relating billow/3d shaping to cell width etc.,drawings and small scale models till I was confident it would work.
For the front cloth between the upper and lower skin at the 3d shaping seam I alligned the cloth 45° regarding fill /warp as I saw this being done to some paragliders which decreased some of the wrinkles in the nose region and allowed more stretch for the front billow. I thought it could do more good than harm so I just tried it.


The main Issue I have now with the bridles is because of the built in billow the kite will shrink of course a few cm in span so ideally I would directly build the bridle already to that blown up geometry which (I think) none of the programs will calculate for me. (I could be wrong here) I don´t really know the billow function of SP as I did most of it with excel/manually.

So I have multiple ideas:

-Build a kite in surfplan which I manually shrink acc. to my excel figures and then export the bridles

-Draw a front view model of the blown up kite on a 3mx3m piece of thick PVC pattern material in a model scale and simply draw the bridles. (I can be quite accurate with the vertical positions of the attachment points and even twist of the wing, but I will loose the 3dimensional measures of the bridle rows and diagonal travel of the different levels towards the mixer (compensate with pythagoras maybe)

-Just build a model of the kite/bridle rows with twist and everything in Auto CAD and proceed as above but with 3d measures.

-Rebuild the kite in Paratailor CAD and use the billow function and just get the bridle of deformed/billowed kite via direct export.

I´m not very happy with all of these methods as they have their areas of errors and approximation.

The question is if these methods are more inaccurate as just assuming bridle from the original undeformed kite in SP.
Its not such a big issue though as building the bridle takes half a day and can simply be removed and redone and I have lots of bridle line but anyway I want to get it as close as possible to real flying shape straight away.

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Mon May 11, 2020 9:16 pm

You worry much too much about how billow affects to bridle. It is quite constant factor affecting only span wise so it really doesn't make that much difference, primary bridle angles just change a little bit when kite takes its billow shape when it is flying. IDK if SP takes this "shrinkage" in bridle calculations but anyway it is not that significant.

Your way to build or more design kite sounds interesting and your work with cell shaping is admirable. 3D shaping in LE is at least interesting try, hard to say how significant it is though.

You can adjust billow in SP and also check how billow (cell shape when kite is inflated) looks like. What are the correct values is different question and again cell measurements affect it.

I suggest you just make a bridle in SP, it will be fine. You can try to adjust matching billow also but like I wrote it isn't that critical. Foil kites are really not that critical to shape, for example you can change the amount of canopy curve by the bridle without much issues as long as it isn't too drastic. Shape errors should be avoided though, they make kite fly poorly. If your kite looks good in the air, wing is smooth and all line rows support it appropriately it is all good.


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