Are your eyes better than mine?

I've been watching and re-watching this video of a kite flying (I can't make Vimeo embed).

It's based on the tetrahedral kite, a tried and tested design.  In my experience, kites like this have amazing stability and huge amounts of lift.  This thing should have needed a serious effort to restrain.

But it only gets a few feet off the ground, and then only just.

The huge banner will have something to do with it, but not a lot.

I've squinted at the video of it in flight, and I may be imagining it, but are a lot of the triangular cells the wrong way round, contributing no lift at all, just a lot of drag?

Can you have a look, and see if you can work it out?

Picture of Are your eyes better than mine?
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canucksgirl5 years ago
It looks like there are wires holding the structure together. I wonder how much weight that would add to the design? If it wasn't that windy it may contribute to their lack of lift.
wires.jpg
lemonie5 years ago
I look at that and I see black; how the hell are you going to get air through it if it's blocking light?
The unit-concept hasn't been scaled-up right.
(Or alternatively "what the hell kind of "wing" is that eh?")

L
Kiteman (author)  lemonie5 years ago
Cellular tetrahedral kites are opaque from the side, but not from the front (or back).

(I haven't made one for ages - I'll add it to my to-do list for the spring.)
lemonie Kiteman5 years ago
There's too much drag & interference, or tendency for air to go around the cube.

L
PKM5 years ago
It would help if the video was at all interested in showing you how the kite is made, rather than lots of deliberately shaky-cam out-of-focus overexposed arty buggering about.

That's my problem with most of the stuff I see on NOTCOT, actually- all style and very little substance.

</crotchety>

I'd imagine that they have problems with self-occlusion, whereby the faces inside the cube don't contribute any lift because they are in the wind shadow of the front faces, so the overall lift is proportional to size² whereas the mass is size³. 

A quick Google around shows me that most multi-cell tetrahedron kites are constructed like Sierpinski gaskets with large internal voids, which I'd guess eliminates this problem.
Kiteman (author)  PKM5 years ago
I've just exchanged emails with the kite's designer (Sash Reading) - you're right, it's the dead-weight of the inner cells.

He said:

The lack of lift was due to the sheer mass of the structure - it was fully celled all the way through, with every edge of each wing containing a carbon spar. this added to the aesthetic but greatly hindered its flying ability. ultimately its an installation rather than a kite, so just the mere fact that it lifted into the sky (albeit rather clumsily) was enough to jsutify it as a kite and a sculpture

rimar20005 years ago
Sure that my eyes are worse than yours, KITEM. I only see a triangle out of alignment (center of my image). In my humble opinion, the reason is very simple: the structure is too heavy for that surface. Each triangle would be a square, in which case the lift force would be doubled.

I agree with you in that banner can't influence too.
Kite.jpg