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A concept for the world's biggest, longest, widest kite?

Can possibly be used for sailing straight up or down wind

Copyright © 2005 - 2009 Anders Ansar. All rights reserved. You are welcome to use pictures and words as long as you include a link to my pages.

Here the kite rises in an arc in the wind. It is controlled by the persons at the ends. The size is 22 x 0.5 m. With this size the center didn’t lift so we cheated using a string attached to the center and held by the person on the table. Smaller kites do work without this extra string, see below for possible reasons.

Abstract 

I set out to make an easy to make high performance traction kite: good  Aspect Ratio, smooth surfaces and low weight for its surface. Thinking outside the box I came up with a ribbon flown from two distant points, an arch kite. It has ultimate low weight – only the weight of the single skin material. It can not be used as the traction kites we know today. But it can be used for sailing straight up wind or down wind, the latter faster than the wind. It may also be fun as a toy or indoor kite. It can have more anchoring points than the two. Extreme span and aspect ratio is possible. A concept for the world's biggest, longest, widest kite? When using several anchoring points instead of one you enter a new field of kite design. Any ideas?

 Background

 I came up with this idea when I set out to design the lightest and simplest traction kite:  A kite that has only single skin and no bridles (unlike e g a Para foil, multiple layers of skin and numerous bridles), no stiff parts (unlike e g Wipika, Naish, inflated sections). And not a very curved from wing tip to wing tip (like e.g.Wipika and Naish) which decreases aerodynamic efficiency plenty. 

This is an earlier prototype. It is a flat ribbon of plastic film. It has a wooden stick at each end. Here it rises in an arc in a light breeze. But only to some 30 degrees from the vertical, which means the lift to drag ratio is only about two.

  More about the kite pictured at the very top

At the first try it turned out the fabric folded double so I had to insert some five mm thick wooden sticks from leading to trailing edge. This was a departure from the initial idea of having no stiff parts. But weight increase was very small.

   As I wrote above the center of this kite didn’t lift, so we cheated using a line at the middle. A reason could be the cheap fabric was so elastic that  we could not steer the middle by manipulating the ends.

Indoor kite

Here I am walking towards the camera with a kite made of thin Mylar film. You can make a larger one to be flown by two people, one at each end.  There are no battens except at the ends. The gray lines are just the tape at the broad seaming which gives the foil camber.

  Extremely large span, 200 m?, and aspect ratios, AR, 200?, possible. A 16 men team sport?

With this design extremely large spans becomes possible, maybe the way to go for the world’s widest kite. Also high AR comes easily which could lead to a kite with low drag. But the kites I have made have not had a good lift to drag ratio, L/D ratio. They have not came anything near the vertical when viewed from the side. If they come close there may be stability problems, the kite collapsing downwards.

    If that happens you can restrain it with lines at the trailing edge. For a large kite, say 200 m long,  I can see some four people controlling each end of the kite (holding a long tube, which goes through the end of the kite). Another four holding lines, spaced at the leading edge, which pulls the kite forward. And another four holding restraining lines led to the trailing edge of the kite. A 16 men team sport.

Maximum possible size and flying height?

Wind is available well above 10000 m. For a very large kite I guess the strength and lightness of the fabric becomes the restriction. Optimal is to orientate the strength in the direction of the span. Sail makers may have some suitable material with carbon or Kevlar fibers.

I made the first kites with a cambered foil

My first kites were made of mylar and had a cambered foil, I let the material overlap a bit in an arc forward and backwards from the 1/3 cord point, from the leading edge, to get camber. I then tried the more “simple to make” flat foil and it seemed to work as well as the cambered foil.

Aerodynamic notes 

See  for example  http://www.bchpa.org/newsletter/may04/barish.htm  for more information on David Barish work.

Sail straight upwind with this type of kite!  

A new traction kite? you say. Not as we know them today. But it can be used for traction. Equip the persons at the ends with  ice skates (I am a skate sailor see http://home.swipnet.se/ansar/s.html), roller skates, surfboard, buggies, cars ......

    Let them face the wind, kite square to the wind. They hold it quite straight. Skates pointing slightly inward from the direction of the wind. Next they turn the ends of the kite making it to raise. They will be pulled towards each other and the will be sailing straight up wind!

   When the kite has risen high the sailors turn the ends of the kite making it loose height . At the same time they change course to outward from the direction of the wind, they now travel on their momentum. Soon the kite is straight again. Then they repeat the same cycle over and over again.

   In order to have a reasonable long cycle the kite must not be to short. For example a 100 m long kite will pull in each end some 7 m before it has risen to around its maximum practical height. If the sailors move upwind 5 meters for every meter they are pulled inwards they move 35 m when pulled in 7 m. If they travel at 5 m/s the traction cycle will take 7 seconds - long enough to be handled by humans I believe.

   To get this working you need a kite with good lift to drag ratio - a kite that rises to around 10 degrees from the vertical, when viewed from the side, ends of kite in line. That angle corresponds to a  lift to drag ratio of about 6, if I got it right (tan 10 = 5.88).

Sail straight downwind, faster than the wind!

It is also possible to sail straight downwind, faster than the wind, with the same technique. First the sailors have to gain forward speed, e g by skating, until they feel wind in their faces. Then they can initiate the cycles described above.

The easiest way to test this type of sailing may be to take a Para glider and run a pair of long lines,  50 - 100 m, from each wing tip to the sailors.

You develop

The idea of using multiple anchoring points opens up for new designs not possible with the usual kite anchored at one point.

What is next? It is up to you! Any suggestions of designs?

Man shrinks luggage to 1 oz, 30 gram.  Or longer a version at: http://sites.google.com/site/travelulcomp/ Is also equipped for more comfortable in hot weather.

When I was almost finished with this page I found the same type of kite at:

http://www.ssk-kerpen.de/sport-seiten/ssk-kit_bild.htm    Have you seen it somewhere else?

An A kind Dutch man sent me the URL below photos of a 440 feet arch kite. Very impressive!

http://www.kitelife.com/archives/issue33/carolina-kf03/

Another kind reader send me another URL of a windbow

http://users.argonet.co.uk/users/parsons/windbow.jpg

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Written June 2005. Modified July 2009