The problem with tetrahedral kites is that the joints have to be able to connect six (6) or more spars coming together (or through) the joint at the same time!!!. This gets even worse if you are like me and want to be able to disassemble or flatten the kite for transport.
After much experimentation, I came up with the following simple method of using plastic tubing to join the spars together, into units of 4 cells each.
A four cell version of this kite I have found to really hate any sort of turbulance on the wind. causing it to roll over and dive-bomb to the ground. In a sea breeze coming directly accross the water, these kites are great and fly well.
If the wind is very high or very turbulent, the kite may loop or topple over. If this is happening you can either: add a long streamer tail to the end of the leading edge; OR you can join more cells together (see below).
The problem is that a four cell tetrahedral is not actually stable. The center of mass is higher than the center of sail area, an unstable situation. Adding more cells to build a larger tetrahedral kite reverses this situation and makes the kite fly as steady as turbulence and weight will allow.
A 16 cell sierpinsky tetrahedral built by joining 4, 4 cell tetras like this plan details, is probably the simplest and easist way of increasing the number of cells a tetrahedral kite has, and thus stabilising it.
Weight is also a major problem with these kites. The plan above trys to cut down the weight while also allowing faster setup, and pack away times, by removing two of the individual cross spars. Unfortunatally this means that the size of the spars also needs to be thicker to prevent too many breakages. A fully cross braced tetrahedral can use much lighter spars (bamboo BBQ skewers for example) but at the loss of set-up/pack-up time.
I have found that if a tetra is heavy it likes to swing from side to side on a relativally short fling line. Note, this is different to wanting to loop or tumble. Increasing the flying line and adding a long streamer tail will generally dampen these effects.
Attaching the flying line directly to the front wind-most corner of the kite also seems to help to stabilise it in the higher winds. Though I like to still use a bridle from the nose and tail of the kite with the rear line just loose when it is flying steadily. By doing this, if the wind suddenly gets on top of the kite through turbulence or a sudden air pocket, the rear or lower bridle line will become taut and stop the kite just falling from the sky, before it has a chance to recover.
Launching the kite is really easy. Just sit the kite, on the rear face with the leading edge facing into the wind. The wind will then just push the kite against the ground preventing it from flying away. It is one of the few kites that when on the ground like this will stay put, no matter how strong the wind. When ready, just pull on the kite line and up it will go.
Their are lots of variations you can try to
the basic regular tetrahedral kite plan above. And many of these will also
improve the performance of the kite.
As I mentioned above a major problem with building tetrahedral kites is
the joints, and thus the reason for this plan. This joint problem gets
worse if you want to make a more solid tetrahedral structure. I would
love to hear of any other methods of joining the kite spars together.
The other problem is weight. 6 spars per cell is required for the kite. Actually it is 22 lengths per four cells with this plan. This is quite a weight and can only be solved by increasing the cell size. More lift and stability is also achieved by using more cells in your kite. The lighter a tetrahedral kite is the better it flys and more stable it becomes.
Alturnative cell bracing methods can allow you to dramically reduce the weight of the kite. However due to the extra stresses tensions required, may require must stronger sparing, or the addition of some curves to the edges of the triangles.
Tetrahedral kites are very well suited to expansion, being a rigid structure a very strong kite can be made, and only seems to get stronger with complexity. As such very, VERY, large kites can be created, from the weakest material, though maybe not so easily transported, unless you can figure out a good system for storage.
TetraLite, has solved both the above problems even better than the solution presented in this plan. If you look on thier pages you will see series of pictures of a 34 cell tetrahedral kite being folded flat into something a mere 3 inches thick. This kite is also so very light in weight, due to the materials used, that the designer claims you could fly it indoors with carful rythmic line tugs! This company by the way does not sell kites, only a $US20 manual on building their tetralite kites, and is an excellent buy, for serious tetrahedral kite builders.
--- Anthony Thyssen.
If like this kite, and build a few of them, please mail me and let me know what you think. Including any ideas, suggestions or other experences. That way I can add them to the plan and others can read of your results. :-)