A standard test protocol for comparing kites

[OliverG]

I agree that it is a pretty subjective thing, determining what makes a kite good. I think we all generally know what we like and with experience we know more as time goes by. So many kites are good, yet in many cases very different from one another solely by virtue of it's design. Take the Windwing Outrage and the RRD Type Wave. They could be compared, but doing so wouldn't result in any meaningful data because they are completely different designs, meant to serve different purposes and they exhibit totally different characteristics. You could compare high-aspect kites as a group, but what would your control be? What's the standard to which the kites are judged or compared?

I like the ones that give me big smiles when I come in after a session and leave me feeling tired and happy.

[knyfe]

The only subjective thing I ever saw was a test in a german magazine where they measured the glide ratio / glide angle of different kites. But this tells you nothing besides that the kite will fly fast in the air. Not surprising the FS Speed was the winner, with the M5 close by.

You dont need to read the german stuff, I think the graphs are self explaining...

http://www.flysurfer.de/downloads/gleitzahl.pdf

But on the water other things are imprtant too as we all know. And everyone has different ways of riding. CU, K

[Sander]

Nice point Bric, kites and (all sails) are functioning works of art! Yes, they are engineered, but definitely getting the design takes some artisan know-how.
Add to that the fact that kites behave dynamically, ie change shape in-flight and hence performance characteristics such as lift, drag, turning speed etc and you may not be able to neatly quantify anything that is really meaningful besides kite size (area).
On the other hand, Leo, I dig all the techno stuff and would be interested in hearing more about the secret test site at the former Oakland Air Base, area 53 is it?
Sander

[charlie]

art..? :?:

[Guest]

art = charlie successfully landing a multiple tea bag all in one jump

[fearlu]

Let's leave Charlie's multiple tea bag out of this...

[lmontejo]

I am fascinated by some of the posts I am reading here.

I am not new to wings (that is what a kite is) and have been flying airplanes for over 30 years. I also fly sailplanes, hang gliders, paragliders, and in all of these disciplines the design of these flying machines comes with a heavy dose of aerodynamics and a minor one in creativity or art as is mentioned here.

Those of you who are writing here that feel is what it is all about need to learn a little more about wings. Even the Wright brothers were doing wind-tunnel testing to improve their wings, and yet I see that some of you here wish to take kite design to the dark ages.

However complex it may be, we can definitely sit down and design a batch of tests, which will grow with time, and that will allow us to compare different kites. Some of the manufacturers may be doing it already. The Crossbow, for example, reminds me so much of an early hang glider wing, that I would be highly surprised if its designer in France has not spent much time with aerodynamic calculations instead of feel.

Kite performance is all about aerodynamics. We can start simple, and build upon the knowledge we gain.

I witnessed the growth and dramatic improvement of hang glider performance 20 years ago, and this was accomplished by putting them on top of vans and measuring how they behaved while driving down a runway. Leading edge battens such as the Rhino 06 is boasting, devices to maintain the trailing edge tips up (I noticed an attempt at this in the Crossbow), etc. where all studied 20 years ago, so please do not be naive in thinking that all that we are seeing is new.

Last week I had the opportunity to ride next to Yuri in Alameda. Both of us were on similar boards, and the wind was blowing some 10 miles per hour. We were both staying upwind, some 10 feet from each other. He was on a Cabrinha Crossbow 12, and I was on the latest Slingshot Octane 16. Two very different 2006 kites, and surprisingly, the 12m one, with much wider range than the Slingshot, was performing just as well (for what we were trying to do, that is kite and stay upwind in low winds). I am not sure that trying to understand what is going on here can be branded just as "techno stuff". It is also related to your pocket. You may decide that you want to buy hype, or try to be more educated, and buy because a given model generates "x" amount of pressure (lift) at a given airspeed, and that it stalls (hindenburgs) at a speed "y". In fact, one of the reasons why a Crossbow has such great range is that its stall speed is undoubtedly much lower than my current North Rhino "C" kite. The Crossbow, with its flatter design behaves more like a wing, and therefore flies (or stays up there) when all pressure is released. From a distance, we were being watched by Jeff Ruoss, who commented that he could see a larger surface area working on the 12m kite than on the 16...

Finally, Sander, all wings behave dynamically. You should see my sailplane's wing while I am flying down the Whites at 18,000 feet. A 60 ft. span sailplane wing has incredible math behind it. They even stress these wings to the point of breaking them. (Think of how much money would have been saved by many if Best had done "explosion" tests on their Cuben fiber kites.) A sailplane today can safely achieve a glide ratio of 50:1! In the case of my sailplane, the wing has 5 different angles of attack, and each part is doing very different things while I am flying along. To avoid these wings from shattering in flight, they are made to be very flexible, and thus very dynamic in the way they change their shape in the air.

I would like to move this discussion more to what tests people believe are useful, instead of the art vs. science dialog it has veered to. Once we decide on what makes a kite "good", we can develop metrics for that.

As for the admirers of artists here - what can I say. They must have deep pockets!

Comments?

Leo

[Guest]

Yeah, I was a little surprised by the anti-techie sentiment as well. I read a ton of "enthusiast sport magazines" and not one of them ignores the "science and numbers" of gear perfomance. They always have a dose of how the equipment feels and how it stacks up numbers-wise.

Don't be discouraged-- I think some of us are interested in the empirical data you might provide. Unfortunately, I will not be able to assist you though, since I will be busy this winter snowboarding and won't have spare time to spend indoors.

DL

[David (guest)]

Gee, I'm not sure where all this is going, particularly the "art vs. technology" spin that seems to be creeping in. That being said, please let me add my point of view.

I know a bit about aeronautics, and I'm not afraid of technical details, nor am I wowed by them unless there is something very clever in the design. However, I think that a lot of the empirical data on kite design is really more useful in the hands of the designers, not the consumers. And we all know this is being done. At the end of "The Complete Kiteboarding Guide" there is an interview with Robby Naish, where he talks about ocmputer modeling of kite performance. This is no surprise. What would surprise me is if end consumers found a way to make good buying decisions based on lift/drag ratios, stall points, etc. I really think this is the domain of the designers.

So we are stuck with the difficult task of evaluating kite performance in a subjective way that is still useful to a range of potential users. I come to this sport from the sport kiting world, where this issue has been addresssed, to some extent. It's not an original idea, but I offer that if you read multiple kite reviews by a single person, and you know something about that person's style, technique, and preferences, you can make *relative* comparisons. Car reviewers do this as well.

My suggestion, then, is we form perhaps a panel of reviewers with different flying backgrounds/preferences/technique, and have each of them review a set of kites. Once we find a way to "calibrate" our tastes to theirs, we have a decent, if imperfect, way to evaluate their impressions. Calibration may just be a function of knowing them, flying with them, or perhaps flying gear they have reviewed and comparing their impressions with ours.

In the sport kite world this works well. I know how some of the reviewers fly, and have flown some of the kites they've reviewed. If they say a kite "feels light on the line" or "requires snappy inputs to the line", I know what that means from my own experience. And I know whose taste is like mine, whose opinions I trust, and who's evaluating criteria that have no meaning to my own flying style. This seems to work.

Okay, so that was $.05, not $.02...

cheers,

David

[Guest]

You guys may want to consider contacting kiteboarder magazine. They might be happy to help with your endeaver. They too attempted to compare a bunch of kites in controlled conditions, concentrating on light winds. Check out the August 2005 issue. In the end, they decided not to go the route of science and numbers, but originally they had planned to do this. I'm sure they would be happy to help you guys. They are a magazine run by kiteboarders, for kiteboarders. Who knows, they even help fund this type of research.
-bric