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DIY Foil Kites

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kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Mon Dec 10, 2018 1:56 am

Hi Schietwedder and welcome to the forum.

I answer quickly some of your questions, which I can and see most essential of.
Schietwedder wrote: Maybe i should also use surfplan instead of Foilmaker, with depower briddle and primary secondary and third briddle the program is at the end of its abilities
Absolutely. SP is state of the art program, Fm is primitive one which lacks so many things. Mastering SP takes quite a lot time and preferably couple of hundred kite designs at least. I have about 30 for this year.
Schietwedder wrote: I have some profiles from Ozone R1 and Chrono, maybe i just copy and paste them hehe
Yes, but remember those are race kites. Consider always how much camber (or lift/stability) you need. Airfoil selection is one of the big questions of kite design. If you want to import an airfoil to a design program you must know how to do it.
Schietwedder wrote: New profile for shure (Advice? Some reflex for shure and i dont have any idea with the leading edge and how much camber and where to put the max depth
Usually max depth is quite near LE in foil kites. Don't put too much camber in your airfoil, it will make kite too unstable for depower.
Schietwedder wrote: Now im planning something Closed cell, AR 6-6.8 11m2-12m2 race foil-ish 25-30 cells like the minima.
Closed cell is ok, but don't go big and even less for big AR, not at least to 6-6.8. You will risk a failure and mid AR kite has very decent performance in much easier concept. You must study which cell count suits best for your AR and for structure in general. (If you don't have D-ribs it is not that critical though.)

You have good basis and equipment for your next kite project. Don't rush it but do design work carefully and study how kites are made and try to think how different parameters should be. There is lot of details in which designers won't give advice because it is their intellectual property collected by the years of work, both successes and failures. No one else but you can design a kite which is designed by you.

Good luck :thumb:

Regis-de-giens
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Re: DIY Foil Kites

Postby Regis-de-giens » Mon Dec 10, 2018 9:25 am

Congratulations Schietwedder,
It is nice to see young people doing their kite up to actual fabrication.

If by chance you are looking for a beta tester of your small closed-cell kite, then oriented feedback on several supports (static , hydrofoil and snow) i am volunteer !!! :thumb:

klimm
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Re: DIY Foil Kites

Postby klimm » Sat Dec 15, 2018 10:29 am

Hi guys,
looking for advice concerning the transformation of an old paraglider(Vulcan from Ozone) into a snowkite by eliminating some of the central cells until reaching a reasonable surface for a 65 kg rider. Course the lines system will be the difficult part. Is this feasible by trial and error, or should I forget it?
Please recommend me a lines system with depower, I could use as inspiration.
As an ex backpack and sleeping bag designer, sewing is not a problem. I also have a good grasp of geometry and developed some tools for developing paragliders, in Autolisp, very long time ago(abandoned)
About flying; I fly paraglider since 91(I'am 57) had a snowkite only for a winter, to test it, was big with 12-16m2, (don't remeber) but enjoyed it a lot.
I'm on skis and sometimes, use to ride an old Peter Lynn 2 liner, about 2.5-3m2, so no harness (well sometimes in predictable winds I hook up my climbing harness to it with some primitive quick release system, I improvise :) )

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Sat Dec 15, 2018 3:28 pm

klimm wrote: looking for advice concerning the transformation of an old paraglider
Short advice: It is not worth it. At best it will be a very slow kite with enormous pull. Perhaps with it you can tease other kiters at 6kn but 9kn you will suffer. For example 26m PG-kite pulls ridiculously more than any other kite :o
klimm wrote:Please recommend me a lines system with depower
It is very possible it will not allow depower, at least that one I converted didn't. When depowered high camber wing has huge lift until it reaches the point it front collapses.

Original lines will not do, but it is not difficult to measure canopy and to make similar model with reasonable bridle in kite design program.

If PG is in good shape you have in it good material for kites. If you want to have a DIY kite just design one and sew it, apparently you have basic skills to do it.

klimm
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Re: DIY Foil Kites

Postby klimm » Sat Dec 15, 2018 5:45 pm

Thank you for your answer kitexpert.
I know it is not wort the time, but seems like a nice anti alzheimer project. I actually am only interested in snow kiting and we have little snow where I live, a few days kiting worth a year. Not worth to buy one, anyway. This would justify the try. The Glider I sacrifice is a class2 DHV with 56 cells. Profile is relatively thin. I already played with it, as is, and as you say, has a huge pull but I am 67Kg and the thing is 22 m2. Nice to use up hill. Looking at the lines plan I identified 2 places where I could cut it and use the original achor points of the line system; I could get a 7m2, or a 12m2, by sewing the tips together. But first I need to see how smooth the two parts would merge together for the two versions. I suppose I should build the 7m2 in order to have thinner profiles and smaller surface.
As the glider has a speed bar, I thought the profile would be fit for a power modulation of a sort, but the speed mostly acts on the central cells which I will cut out .
I read a bit on this forum and I will take a look at SP for the lines plan(bridle) but as you said somewhere, this will take a time to learn.

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Sat Dec 15, 2018 11:05 pm

I meant it probably is not worth for the result. I don't think that DIY work with kites is at all wasted time, you will learn a lot for sure and will have some work for your brain :thumb:

I wasn't thinking that radical cut down and if you do so most "valuable" part is left aside. I mean biggest (or only) advantage of that kind of project is that huge pull which is available. The challenge is to make it usable and to decrease it to tolerable level.

The more you cut it the worse parts fit together. Or there will be an angle in where parts join, which doesn't look nice.

I checked how Vulcan looks like and I see couple of appropriate section points, that is to take 8 or 10 cells away from the center of the wing.

Image

With 46 cells it could be like that. If you give me some measurements of your kite I can give you exact bridle line lengths.

klimm
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Re: DIY Foil Kites

Postby klimm » Sun Dec 16, 2018 11:10 am

Thank you for wasting your with me :)
When you said it is not worth I was also thinking at the PG profile which is different from profiles used in kites, so, in a way will be a hopeless project.
You're right, but what to do with a huge(46 cells) 15 to 17m2 big kite, with a central depth of about 2.7m. This would rather become a big speed glider, to soar in stronger winds which was my first thought in spring when I bought the new PG. I still can think of that if the kite conversion will not work reasonably.
I agree the parts won't merge smooth, the shorter I cut. If I cut one cell above k8 for 7m2 , would be really ugly but usable, and one cell above k6 for about 12m2 would be aesthetic acceptable, but already is too big for my 67kg (if I cut 20 cell from the middle)
From your picture I see the lines plan rather similar to one used on water right? Or am I in error?
As you see we have about 4 levels of anchor points in the canopy that we could use in order to achieve a lines plan rather like a snow kite (open cell, maybe with a mesh of some sort) with a depower system.
I don't get the precise meaning of bridle. Does this refers to all lines(lines plan) or only to the (A) front ones. As said I am new to kiting and also not an native english speaker.
Back to the subject: I laid down the glider and put the parts together for the 12m2 version which might be the best compromise between what you suggest and what I would like but don't think will work. I will cut (count from center) at cell 9 1/2 so that when sewing I will work in fabric with no stitches.There will be a sewing in the middle of the cell (not on a profile) which is not a functional issue, a rather aesthetic one. This way I also use the existing diagonal ribs that are built into the canopy. In the middle I would then get a 3 cell field with no anchor points, then AM3, AM4, and AM5, AM6...
The length for the above is 3,5mt for a side, measured flat on the inner skin, with the fabric tensioned a bit for acuracy. So total 7m but this don't account the curvature so projected would be less.
The flat span should be close to the projected span for the central 20 cells, measured 4.2m. The projected span for Vulcan S is 9.22 subtracting 4.2(20 mid cells) = 5m (approx) projected span for our kite.
The depth of the profile at cutting point is 2.45m, at 1,3mt from the tip, we have .1.86m
As I can estimate, the axis of PG is elliptic .
There is a table with all chords in the manual if this would help to determine the PG elliptic axis..

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Sun Dec 16, 2018 11:56 am

klimm wrote: but what to do with a huge(46 cells) 15 to 17m2 big kite, with a central depth of about 2.7m.
There is many bigger kites. 15m kite is not that big after all. High cell count is an advantage, I wouldn't sacrifice it.
klimm wrote: above k6 for about 12m2 would be aesthetic acceptable, but already is too big for my 67kg (if I cut 20 cell from the middle)
12m2 is usual kite size, not especially big at all. Of course PG-kite is stronger and it very probably will not have much or any depower, but this kind of project has clear aim to be a light wind kite. If wind is very low size is not problem, no kite is too big.
klimm wrote: From your picture I see the lines plan rather similar to one used on water right?
Yes, it is a usual kind of bridle of a foil kite. Intended use doesn't matter.
klimm wrote:As you see we have about 4 levels of anchor points
Vulcan has many line rows, some of them could be left unused or cascaded together (like B already has been done).
klimm wrote: I don't get the precise meaning of bridle. Does this refers to all lines(lines plan) or only to the (A) front ones.
The bridle is whole thing, all lines which line plan includes. My quick design shows just A for clarity. Other rows are more or less similar.
klimm wrote: I will cut (count from center) at cell 9 1/2 so that when sewing I will work in fabric with no stitches.There will be a sewing in the middle of the cell
No, don't do that. Don't cut anything, just undo seams and then resew.
klimm wrote: This way I also use the existing diagonal ribs that are built into the canopy. In the middle I would then get a 3 cell field with no anchor points
Yes, you should use existing D-ribs and make joining so that they are taken care of. 3 cells in the middle without bridles is ok.

IMO you are going to cut it too much, at least don't go below 12m2.

klimm
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Re: DIY Foil Kites

Postby klimm » Sun Dec 16, 2018 1:27 pm

Of course there are bigger kites but we talk snow kite only, and I am only 67 Kg. I just asked some kiters. (about 80kg and above) and they said they never ride over 12m2 on snow, because of the little drag of this. A lady with my weight said; nothing above 7m2 worked for her, except rare occasions when they had a really low wind(3-4) As you know the wind can get stronger, mixed even with thermal activity. They use to kite on a plateau about 1500m in the near mountains. I also play here, at my place, above 7m/s with the small one. You can see here the hills ( after the 1st minute )
front wind was 7m/s and the PG was almost standing https://youtu.be/VEseyoRNARE
I understand the project is a light wind kite, also because of the profile which for sure is slow in relative terms, compared to kite profiles. This is actually my biggest concern.
Technologically speaking, from my experience, resewing over a line of stitches, that already weakened the fabric, will be worse than sewing on untouched material. Much worse. I always repaired PGs, only this way, after seeing failures the other way. Of course doesn't look so nice.
Would you be so kind to make me a bridle proposal for the 12m2 as described in my previous post or the data I provided is not enough?
You don't have to of course, I mean I don't want to abuse of your time.

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Sun Dec 16, 2018 3:22 pm

Yes of course I can design a bridle for 12m2ish kite for you, that is actually a good point where to cut and size is reasonable as well.
klimm wrote: Technologically speaking, from my experience, resewing over a line of stitches, that already weakened the fabric, will be worse than sewing on untouched material. Much worse. I always repaired PGs, only this way, after seeing failures the other way.
Ok, my experience is different, actually I've never seen kite failure from the seam repair. PG's (which I've worked with) have wide seam allowances and double seams, in general structure is much stronger and of higher quality than what kites have. Many times I can hit old needle holes, at least partially. Very important thing is alignment marks which will be there if seam is undone and which is not there if cell is cut. I warn if you don't have experience how to sew ripstop you risk considerable alignment error without marks - even with them closing seam is not very easy to do.
klimm wrote:I mean I don't want to abuse of your time.
Not at all, if I can help and if project is successful there is enough payback for me :wink:


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