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DIY Foil Kites

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kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Sun Dec 16, 2018 3:39 pm

If you want to cut in the middle of the cell and you are sure you can sew it correctly I don't disagree with it. Actually it makes kite cell count odd (which is usually better) and there will be 3 cells in the middle without bridles which is also acceptable.

I suggest one thing: lets count cells from the tip, meaning number 1 cell is tip and so on. Thats the way I've used to do it :)

Now there should be 37 cells if you cut cell in the middle of a cell or 36 or 38 cells if seams are undone. Is that ok for you?

I need chord length (depth of wing) in the middle (at the join) and span length of the new kite (two halves together). Also cell shape is good to know, meaning if cells have same or different width/length ratio or not. Wingtip chord length also should be known. Cell count is of course needed (36, 37, 38).

klimm
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Re: DIY Foil Kites

Postby klimm » Sun Dec 16, 2018 4:10 pm

A problem with PGs is that at the profile front or anchor points along the profile,, there is often a mylar or the like that behaves like an edge and weakens the inner of outer fabric. Stitching does it too where back and forth stitched. I better don't disturb these areas.
No problem about marking , I'm used to this from sleeping bags.
Now, I started to play a bit into SP and looks relatively intuitive.
I just aproximated the shape as I can't precisely determine the canopy curvature. I also will need to measure some profile chords(yeah they a re curved and won't be also precise.
From that video I sent I extracted a picture at 3;24 being seen from the pilot in order to determine the projected shape in Gimp. Flat don't looks encouraging
From a picture on the net I will get the curvature depth, and see if I will keep the same when cutting the 20 cells

Sorry, I am not able to attach the .sle file as it is not an acceptable format for the forum it says?

klimm
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Re: DIY Foil Kites

Postby klimm » Sun Dec 16, 2018 4:38 pm

Sorry I didn't see your last message but the previous only.
we will have 37 cells. I started the project in SP with that count to train a bit with the bridle
I see the SP counts as you propose; agreed :)
As I was able to measure the chord is 2.45m at cell 18 and 1/2.
The flat span would be 7m and projected would be 5m
Cells are wider towards center(1-2 cm) I can measure each when needed but they also differ towards leadin and trailing edge I just gave the program they are equal. The length width ration will vary as I can see.
While the tip is curved and PS only accepts straight for this kite, what chord should I give?

klimm
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Re: DIY Foil Kites

Postby klimm » Sun Dec 16, 2018 4:50 pm

I measured the chords 1,2,3
the tip-1=38cm 2=62 3=85
Of course the chords can't be exactly measured but 1 is for sure 38

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Sun Dec 16, 2018 5:32 pm

klimm wrote: A problem with PGs is that at the profile front or anchor points along the profile,, there is often a mylar or the like that behaves like an edge and weakens the inner of outer fabric. Stitching does it too where back and forth stitched.


That is true.
klimm wrote: No problem about marking , I'm used to this from sleeping bags.
Ok, but I meant there is factory alignment points in seams. If and when you cut the cell there is none but you can of course mark some by yourself. Just be precise.
klimm wrote: Now, I started to play a bit into SP and looks relatively intuitive.
Yes, basic things can be done quite easily with it.
klimm wrote: I just aproximated the shape as I can't precisely determine the canopy curvature.
That is ok, there is actually quite a lot leeway there because foil kite cells hide small errors.
klimm wrote: While the tip is curved and PS only accepts straight for this kite, what chord should I give?
? You can adjust canopy curve and plan shape in SP very freely, also manually.
klimm wrote:Cells are wider towards center(1-2 cm)
But middle cells are much bigger than cells at tips. Is difference really that small? Hard to believe.
klimm wrote: Sorry, I am not able to attach the .sle file as it is not an acceptable format for the forum it says?
I don't know how to do it either but it is not necessity. Designs I've presented here are just screen shots.
klimm wrote: we will have 37 cells. I started the project in SP with that count to train a bit with the bridle
I see the SP counts as you propose; agreed :)
As I was able to measure the chord is 2.45m at cell 18 and 1/2.
The flat span would be 7m and projected would be 5m
the tip-1=38cm 2=62 3=85
Ok, 37 cells it is. Here is new design from these values.

Image

klimm
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Re: DIY Foil Kites

Postby klimm » Sun Dec 16, 2018 5:49 pm

Looks good,
for the whole PG I computed a curvature height of about 250cm for a projected span of 922cm
What is the curvature height at your design?
sorry I was in gimp for a while

klimm
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Re: DIY Foil Kites

Postby klimm » Sun Dec 16, 2018 6:01 pm

In order just to translate the two parts resulted by eliminating the 19 central cells, this means keeping the absolute curvature height at 250 cm, I computed in the Canopy Shape dialog box, a curvature height of 50 (suppose it is percent)

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Sun Dec 16, 2018 6:43 pm

You can decrease curvature height because you have decreased wing span. PG's have quite high projected area (low curvature) so I think 50% is a bit too much for it. In design above there is 44% curvature at 46 center/tips. Just adjust it how you like it, but don't go too far away from the original shape.

Practice SP and try to make your own design something like above. Design above is too raw you will have much use for it, for example you must measure bridle point locations from the chord (in %) and decide which of them you will use (SP has a limit of 5 for line rows).

Also cell width and how it changes in the canopy I've just guessed something. Measure that as well and adjust "rib spacing" in SP to match it.
Last edited by kitexpert on Sun Dec 16, 2018 6:47 pm, edited 1 time in total.

klimm
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Local Beach: will kite just in the winter, on skis
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I just borrowed a kite to get a grasp of it and liked :)
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Re: DIY Foil Kites

Postby klimm » Sun Dec 16, 2018 6:45 pm

I thing I screwed up something. The canopy is not in my workshop but in the house. was working with my first measurements and guestimates from yesterday.

[/quote]But middle cells are much bigger than cells at tips. Is difference really that small? Hard to believe.
klimm wrote:[/quote]

It is maybe late but I measured cell by cell somewhere in the middle of the chords;
Is this still relevant?
cell 1=8.5cm 2=11c, 3=11.5cm 4=13.5cm 5=14.5cm 6=16cm 7=17cm 8=18.5cm 9=19cm 10=20cm 11=20.5cm 12=21cm 13=22cm 14=22.5cm 15=22.5cm 16= 23.5cm 17=24cm 18=24cm 19= 12 cm (this one is the central cell)

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Sun Dec 16, 2018 6:49 pm

klimm wrote:
Sun Dec 16, 2018 6:45 pm
I thing I screwed up something. The canopy is not in my workshop but in the house. was working with my first measurements and guestimates from yesterday.
But middle cells are much bigger than cells at tips. Is difference really that small? Hard to believe.
klimm wrote:[/quote]

It is maybe late but I measured cell by cell somewhere in the middle of the chords;
Is this still relevant?
cell 1=8.5cm 2=11c, 3=11.5cm 4=13.5cm 5=14.5cm 6=16cm 7=17cm 8=18.5cm 9=19cm 10=20cm 11=20.5cm 12=21cm 13=22cm 14=22.5cm 15=22.5cm 16= 23.5cm 17=24cm 18=24cm 19= 12 cm (this one is the central cell)
[/quote]

Yes that is relevant. That wing has thin cells which mean it has clean shape. Respectable values.


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