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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Wed Dec 05, 2012 6:10 pm 
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ChristoffM wrote:
The fat leading edge gives so much parasitic drag to kites that it is an easy way to make all the kites stable overhead. With this drag gone, you would either have to keep the kite powered up well when overhead so that induced drag and increased lift force will stop the kite over flying the wind window, or you would have to add a fifth line to add drag when you are not up to speed yet.


or you can just fly the kite. it wont hindenberg if you sine it a bit, it might circle up overhead behind you but you can just circle it back again

i dont think we need to start over designing the kite before it's even built


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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Wed Dec 05, 2012 7:46 pm 
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Custom purpose-built speed kite/wings can be easily made and the kiteboard configuration is not far off Sailrocket. What is lacking is a dedicated engineering program with proper funding to develop a kite-propelled low-drag vehicle beyond a few hardy guys with recreation-based kites in strong winds.


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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Wed Dec 05, 2012 9:06 pm 
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........With a no size .....High wind...... Infinity kite :wink:


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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Wed Dec 05, 2012 10:21 pm 
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HOW many of you have flown the REV1.5 or REV-ll kites ?

Yea -- Ya gotta kinda FLY them "All the time" , you can't just
lightly hold on while they fly themselves.

They do backwards figur-8's , just as easy as they do them
forward !

On a land buggy -- they "Up-wind" Way better than a foil ; they
will pull the buggy Really Fast as well !!

Bille


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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Wed Dec 05, 2012 10:35 pm 
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I tested the 4 m Powerkite from Rev this year: its too soft, not strong enough for use on water
Its the same with Peter Lynns C Quad


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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Thu Dec 06, 2012 5:44 am 
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Quote:
On a land buggy -- they "Up-wind" Way better than a foil ; they
will pull the buggy Really Fast as well !!


Wow, did not think that would be the case. Those kites don't even have a proper aerofoil shape. Just shows how much kites can improve if we take away the fat leading edge.

Quote:
or you can just fly the kite. it wont hindenberg if you sine it a bit, it might circle up overhead behind you but you can just circle it back again

i dont think we need to start over designing the kite before it's even built


Yes, you are right, but then again I would love a super lightweight super efficient kite to go cruising with in light winds, which is why I would invest time in designing one. If it works then I would definitely also want a strengthened version for speed in high winds. Mind you, depending on the strength of winds one would design the kite for, flying a super efficient kite in very strong winds without a drag system to make it stable could be quite a handful. Then again, with such an efficient kite one would probably go for speed in much lighter more manageable wind. For proof of concept yes, no drag is needed sure. But I think such a kite will have a future as an awesome cruising kite if it can be made stable.

I would not be surprised if kite company R&D teams have kite prototypes lying around that would have been awesome racing kites, but Hindenburged just too easily for the kites to reach production?


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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Thu Dec 06, 2012 6:46 am 
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This thread is beginning to lose its way.

Further to my detailed comments on page 4...

Speed kiteboarding will leave speed windsurfing progressively farther behind because kiteboard lateral resistance and propulsive forces act in relative alignment with each other, thereby minimizing heeling forces, unlike most other sailing craft.

However, though kiteboard speed technology is in its relative infancy and will advance to achieve much higher speeds, it will ultimately fall behind purpose-built speed machines like Sailrocket.

Sailrocket and other current and future competitors aren't constrained by arbitrary requirements like having a 'board' as part of the assembly (as kiteboards obviously are), so they can focus on purity of design, including perfectly aligned lateral forces and reduction or elimination of all extraneous drag-inducing elements. Something like Sailrocket could be a lot bigger, more aerodynamic, more stable, safer, with fewer areas of surface interface (just one*, actually), and consequently way faster.

For archival searches from the future, I confidently predict 100 knots isn't insurmountable, on water, powered by wind :wink:

*To anyone working on such a project, feel free to PM me regarding the concept of a stable design with single surface interface, if you're not already there!

Cheers,
James


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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Thu Dec 06, 2012 8:57 am 
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Below a specially tuned Best Cabo (wavekite!) . Peter Stiewe built it for me last summer. Its a step in the right direction: It has a thinner leading edge made of cuben fibre and a flatter sail profile (less belly).
Its not only 2-3 % faster - it delivers also way more fun in "normal" kiting. You fly over the water and dont have to worry about gusts. :thumb:

To make those kites stable you must make their aspects lower. The Cabo is a mid aspect kite.
The rule is: the thinner the leading edge the lower the aspect has to be. Upwind performance stays the same.
By the way Catman used the mid aspect Genetrix origin instead of his high aspect hydra in his latest runs in Lüderitz :wink: As especially on downwind courses stability in the wind window is the key for speed.

Stability and control are the most important things anyway if you go out in a hurricane and want to go fast. Kiters have had a big advantage in this aspect since the beginning. With thin leading edges combined with low aspects we enforce this strength even further...

Image

http://www.youtube.com/watch?v=ATvsEzWR ... e=g-crec-u


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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Thu Dec 06, 2012 5:16 pm 
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Quote:
The rule is: the thinner the leading edge the lower the aspect has to be.


I think this supports my idea that all kites need some drag to fly with good stability. High aspect ratio kites have less induced drag and therefore need a bit of a fatter leading edge to keep stable. Thinner leading edge kites have so little parasitic drag, that they need to be lower aspect (and hence more induced drag) to be stable again. For a high aspect thin leading edge kite I think one will need some drag inducer, which you only remove once cruising at high relative wind speeds.


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 Post subject: Re: Back to the drawing board- how will we beat Sail Rocket?
PostPosted: Thu Dec 06, 2012 5:27 pm 
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sheet in


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