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DIY Foil Kites

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kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Wed May 02, 2018 12:21 am

:thumb:

Your kites are unconventional in some respects, but what is most important performance seems to be good. There is also undeniable benefits to have relatively low cell count, like you explain correctly.

I like how the bridle is designed, it is quite logical and simple. Perhaps total length of it could be a bit shorter, esp. third level of it. ZI 11 and 12 lines can be shorter. You don't have to follow bridled ribs for Z (it is totally free if they are at 100%), I wondered if it was possible to cascade three Z primary lines together and to have only two secondary lines instead of three.

Plan view of the kite is nice and classic elliptical shape. Canopy curve is a bit mild to my contemporary taste, but you have solid arguments for it too.

In general I think designer must be able to give reasons for every part in his kite.

C-line row D-ribs are less than optimal because of their low angle, but hard to say if it is a problem after all. If you had C line row bridled on every rib you could leave them, save some weight and have full line support there. Different line rows can very well be different.

And how about half-cell D-ribs? If you want to keep low cell count but to have smoother upper skin (which is most important) they are worth considering. If you make them from A to C and continue from there with miniribs you can have practically doubled cell count on upper skin. In the early years I made some kites with half-cell D-ribs, they worked fine.

I also like how you present your kites, bridles/lineplan and details. But I'm not sure if bridle/mixer adjustment descriptions are correct (is lower camber or lower AoA really better for upwind? - it may feel like it but feeling is not necessary the truth...) But these are not very essential things and it is good to have a possibility to adjust anyway. BTW there is some problem to scroll down to see line lengths of 15m kite.

That lollipop is cool :D

foilholio
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Re: DIY Foil Kites

Postby foilholio » Wed May 02, 2018 4:36 am

Kit expert you are like the wine taster of kite design arn't you?

The bridle row placement seems to give moderate camber increase with AoA. I am surprised the Kit expert is not lambasting your arse over it :-) This is unlike more modern designs that have higher camber increase. I think the Kit expert is more vintage Horse and Cart over F1 type of guy though.

I am concerned with what seems a jump from first prototype to production? I may be missing something given the time to release more testing is being done I guess. If commercialization was the goal wouldn't have Chinamen making the prototypes been more efficient? I guess you are so stoked with your design you then decided to sell or others tried and wanted to buy?

Lastly the lollipop ,excellent, surely a bit of Alicudi special mixed in :-)

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Wed May 02, 2018 9:59 am

Image

If I had to design 25 cell AR6 kite with almost 90% PA it would be something like that. Half-cell D-ribs and seamlessly continuing miniribs make upper skin cell count practically doubled to 50, which is quite high value. Half of the half cell D-ribs can be left out for saving weight and making kite simpler. Bridle is not at all bad even when bridled on every rib (due to relatively low cell count and decent design much less bridle line than in Pulsion for example), also air intakes are well placed.

Watch and learn, foilholio, watch and learn 8)

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Re: DIY Foil Kites

Postby foilholio » Wed May 02, 2018 12:14 pm

Nice doodle, but you have positioned the bridle rows such that your camber won't stay constant with AoA change. So basically you are contradicting your words with a drawing. OMG. Oh and your D-Ribs will never hold much load reduced to a point like that. Further proof of a failed kite draftsman? I am watching and learning you like to copy other peoples work, lack of creative understanding led to failure of previous career?

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Wed May 02, 2018 4:59 pm

Foilholio, please stop now your pathetic arguing for nothing and that constant presentation of your misunderstandings. Of course you don't know leading kite design program shows arched D-ribs like that if it is viewed in wire frame mode. Don't worry patterns of them are just fine :lol:

And good luck finding a kite which has similarly designed miniribs which limit with half-cell D-ribs producing completely smooth transition there (and of course in general 50 cells (for upper skin) in AR 6 kite is quite respectable value).

You know foilholio someone always have to invent things so others can use or even copy them 8) If you don't value of that little detail you can ask stef if it is very trivial task to design correct height for minirib especially for such a wide cell.

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Sandras
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Re: DIY Foil Kites

Postby Sandras » Wed May 02, 2018 6:01 pm

Just wanted to give a :thumb: to Stef for walking the walk! Fascinating thread! Thank you!

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downunder
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Re: DIY Foil Kites

Postby downunder » Thu May 03, 2018 5:27 am

stefmoris wrote:
Tue May 01, 2018 10:46 pm
Sorry for the long silence (in case anyone missed me :) ) but I'm pleased to announce its alive!!

lecca-lecca.com

I've changed my profile accordingly and I've got an ad-banner going on Kiteforum now. I'll still contribute to this thread should anyone want to build build build!!
Nice! Wish you all the best!

I only hope this will not ruin your fantastic hobby :)

Ciao

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Re: DIY Foil Kites

Postby stefmoris » Fri May 04, 2018 9:16 pm

Thanks everyone for the kind words :)

Kitexpert and Foilholio please keep this thread constructive.

Foilholio, I've decided to go to market because yes I'm in love with my kite and yes I have friends who want them now. Love is blind though so only time and indipendant reviews will tell if I made the right decision.

Kitexpert, yes mini ribs for large cell widths are not trivial and all aspects of these low cell counts are challenging due to predicting profile distortion. You have an interesting proposal with D ribs along the topskin at half cell, but I don't see how it saves on complexity/cost or weight. Furthermore I think supporting the top skin without controlling the bottom skin and its differing billow/ballooning will create a profile at center of the cell with a completely different lift vector than the rib. Perhaps I'm not understanding something.

kitexpert
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Re: DIY Foil Kites

Postby kitexpert » Fri May 04, 2018 10:16 pm

stefmoris wrote:
Fri May 04, 2018 9:16 pm

Kitexpert, yes mini ribs for large cell widths are not trivial and all aspects of these low cell counts are challenging due to predicting profile distortion. You have an interesting proposal with D ribs along the topskin at half cell, but I don't see how it saves on complexity/cost or weight. Furthermore I think supporting the top skin without controlling the bottom skin and its differing billow/ballooning will create a profile at center of the cell with a completely different lift vector than the rib. Perhaps I'm not understanding something.
Half-cell D-ribs work well and they are a proven thing. They do give very much same airfoil shape in the center of cell than normal ribs do. Upper skin is the most important part of the kite anyway, so it is not a bad idea to concentrate in improving it.

Your concern of lower skin billowing is justified but with hcs situation there is not worse than without them. If anything I think it is better with hc's because upper skin is less billowed (more straight) and this also makes lower skin more tensioned spanwise. I'm not 100% sure of that, to be certain two similar kites with and without hc's should be made. Those kites I made with hc's looked and flied well.

Your concern of hc's making kite more complex/costly/heavier is of course true. But kite with 25 cells and hc's is less complex than 50 cell kite and it gives higher performance than 25 cell kite. Additional advantage in your case would be having similar minirib height to normal ribs and also having D-ribs at better angle. When using hc's arched there is a weight advantage compared to as high cell count normal kite (counted from upper skin), which should have almost mandatory full D-ribs to keep bridle as simple/as low drag one.

I wish all the best for your effort and if there is something I perhaps can help/give advice I'm more than happy to do so.


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