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Cell shape why square why not triangle?

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foilholio
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Cell shape why square why not triangle?

Postby foilholio » Sun Dec 06, 2015 4:23 am

Seems an obvious question? Seems it would work? The design would be difficult or not? Surely a program would need to be created to aid in the design?

Structurally a triangle is much better than a square. Surely a lot of the internal cross ribbing could be avoided and the construction more simplified?

All the main ribs could sit at 45degrees, mini ribs could be 90.

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Re: Cell shape why square why not triangle?

Postby Tfcm » Sun Dec 06, 2015 6:22 am

The R1 has diagonal and vertical internal webbing.. See the image on the like below.

http://www.seabreeze.com.au/forums/Kite ... /Ozone-R1/

foilholio
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Re: Cell shape why square why not triangle?

Postby foilholio » Sun Dec 06, 2015 6:36 am

yer that is pretty common flysurfer has been using them for nearly 10 years now.

I am talking about making the whole cell diagonal. Basically only a top or bottom skin on each cell. Weight would be one obvious detractor. You would use maybe double the internal material. But maybe because it's a more efficient structure and there's more cloth, you could use a half weight or less cloth.

I am thinking it's possibly a more efficient way of constructing a foil. Could a triangle cell avoid needing a lot of straps etc. Probably not as all of them deal with moving the concentrated forces at the bridle attachments.

There is another internal structure that comes to mind. That's using line inside instead of fabric. That would be seemingly more complicated to construct.

stefmoris
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Re: Cell shape why square why not triangle?

Postby stefmoris » Sun Dec 06, 2015 11:37 pm

Very creative idea, I like it, but I don't think there will be a gain in performance.

I think there will be considerably more chord wise drag from the billow of the triangular cell because it will inevitably taper. A rectangular cell's billow runs straight from the LE to the TE.

I also think there will be very strange things happening on top of the leading edges of adjacent cells, since one will have very little span to the next rib, while the following one will have much more span and thus ability to deform.

The way I see the goal of internal strapping is to keep the overall wing shape, surface area, and profile stable through changes in internal pressure (AOA, speed, etc…)

Without internal straps, changing billow alters the span dimension. I agree triangles are good, but with flexible material they only work in tension. Therefore, without straps, the cells will still bulge, and thus affect overall shape, profile, and surface area. If you have to add strapping, you are back to the beginning again.

I also think it will add exponential complexity to the construction. Triangle cells will only touch rib to rib at one point on the top, and one point on the bottom. So instead of a top skin and bottom skin, you have a nose skin and a tail skin. The tail skin will have to split into a top tail and bottom tail if you want to close up the kite with the trailing edge as the last step in the typical way.

Cool idea though, definity worth modelling up in 3D to see at least what it looks like and how it would affect construction.

I've always thought a molded wing would be cool. Imagine squirting a thin layer of something like hot glue between two layers that are then pulled apart into a two sided vacuum mold, so the inside is filled with billions of hairlike strands giving the kite/paraglider/wing/whatever a perfect shape.
-stef

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Re: Cell shape why square why not triangle?

Postby kitexpert » Mon Dec 07, 2015 2:28 am

I thought that many years ago, but for some of the reasons stefmoris said it is difficult. And kite design programs really do not have that option. Now, when single skins are coming it may have something worth studying. Actually I have made one design - but as I said it is tricky to do when program doesn't have that option.

Gin has used years ago partially that kind of solution, they called it v-bottom. It worked well, but benefits are not very big.

"A rectangular cell's billow runs straight from the LE to the TE." -stefmoris

Actually this is not true. There is more spanvise tension near LE than there is near TE. So, cell billows more near TE. If you make rectangular relatively high AR and (too) low cell count kite, it will distort badly. TE compresses, and so called banana-effect ruins kites flying. If you check some 1990's primitive traction kites you see what it can be.

Miniribs and convex TE (and of course narrow cells) counteract that nasty phenomenon. It is good that you did first two on your new kites.

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Re: Cell shape why square why not triangle?

Postby joriws » Mon Dec 07, 2015 7:52 am

foilholio wrote:yer that is pretty common flysurfer has been using them for nearly 10 years now.
And Flysurfer's concept has been visible to public for many years at their R&D section. This picture is Speed3 kite from 2009.

Image

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Re: Cell shape why square why not triangle?

Postby kitexpert » Mon Dec 07, 2015 6:48 pm

"The R1 has diagonal and vertical internal webbing.. See the image on the like below." -Tfcm

This is classical full-cell A to C D-rib configuration with bridles every third rib. Cell is very narrow as you can see from the front view. Looks impressive.

Used D-ribs could have been "arched" to make them lighter. Perhaps in R2 they do that...

"And Flysurfer's concept has been visible to public for many years at their R&D section. This picture is Speed3 kite from 2009." -joriws

These are H-ribs, much simpler but also lighter than D-ribs. Bridle is on every third cell, but cell is wider than in R1. Pansh has quite a similar picture of A15 on their website.

But OP did not mean these things, but triangular cells.


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