Tetrahedral Kite using Straws

up Back to Tetrahedral Kite Information

Index


What is a Tetrahedral Kite

For information about what a tetrahedral kite is and the inventor of the tetrahedral kite, Mr Alexander Graham Bell, take a look at ``What is a Tetrahedral Kite''.

Requirements

Construction

Step 1.

Using the lightest weight nylon line (almost cotton thread size), in fact sewing cotton would probably do, though may break with wear, I thread five straws into double triangles. Threading is best achieved by hooking the end of the thread in the end of a bit of fuse or telephone wire and passing that through the straws, one at a time. Each double triangle which will form one small cell, or tetrahedron, of the tetrahedral kite. Build 4 of these.

[5 Straw Cell]

NOTE: DO NOT tighten the nylon string tight. Just tight enough so that the straws are linked without any slack. The nylon line streches quite a bit and this is desirable so that the kite can be flattened for transport. Also making the string tight will cause the straws to bend into slight curves.

Also after tying each string I suggest that you put a very small drop of glue (any type) on the knot to stop it slowly unraveling.

Step 2.

Use one of the double triangles from step 1, as a template to cut out 4 covers which will be taped to the straws later on.

Step 3.

Join each pair of cells together by threading string though the straws as shown in figures below. NOTE: the resulting pairs are different. One set becoming the leading cells the other becoming the trailing two cells.

[Leading Cells] [Trailing Cells]

NOTE: the straws will after this no longer be completely flat relative to each other, particularly at the corners of the various cells.

Step 4.

Join the two sets of cells together, by threading the nylon string though the straws indicated.

[Join All Cells]

Note that the front two tetrahedra (in green) are not closed along the tailing edge. But will be supported by the trailing cells (in blue) when those cell are closed by an elastic support (later).

Step 5.

The edge straws of the tetrahedral kite, one pair at front, 4 pairs around edges, are linked together by inserting and gluing a 1/3 straw into them to force them to be one straight edge and not flop any which way it likes.

To do this take two full straws, and insert one into another, as far as you can (but not all the way). The inner straw will buckle along its length as it is pushed into the other straw. Pull it out and cut to about a 1/3 length then carefuly insert it into the edge straws leaving the gap which naturally forms due to the other straws at this joint. When gluing I find that after inserting the straw just placing a drop of super glue on the buckle is enough. The glue will be drawn immediately into the joint locking it tight.

Here is a look at one of the edges. Four straws forming a flat fan, plus one or two (on front edge) more straws more poking upward at some angle.

                      \   \     /   /
                       \   \   /   /
                        \   \ /   /
                         \       /
        ------------------       ------------------
               ==============================
        ------------------       ------------------

Also join two more straws together to form a double length straw to be used as a trailing edge, and to hold the kite open. This will have hat elastic threaded through it later (Step 7).

Step 6.

Cover each of the four cells with the covering material (about the same shape as the diamond shape created by 5 straws in step 1) by taping this along the side edge straws of the individual cells. Warning the straws have a tendancy to rotate so you will have to tape both sides to the straw.

The cover should be reasonably tight, but should not buckle the leading straw to the inside of the other straws in the corners when folded. DO NOT tape the leading straw of the cell (the middle straw of the cells in step 1) to the material. When the kite is flattened for transport, the cover will become semi-loose but shouldn't crumple.

Step 7.

Thread the lightest hat elastic through the two extra straws joined together at the end of step 5. Tie the end of the elastic to the two corners of the trailing cells. Use a loop of thread to tie the center of the trailing cells to this trailing edge straw. Be sure that the thread does not shift by supergluing it into the crack between the two joined straws.

[Trailing Spar]

Using this arrangement, The kite can be flattened by stretching the hat elastic. However you are warned that the kite has a tendancy to spring into its normal 3 dimensional shape at very inappropriate moments. A stack of four of these being even worse. Tying the cells through the middle to hold it closed for transport is recommended.

Step 8.

The bridle should be 6 straws in length or 3 times length of the kites side. The extra length of the bridle is to allow you to set a bridle well forward of the front of the kite.

[Bridling]

NOTE: The bridle is different for different winds and kite size. If set right the leading edge should be almost (but not quite) parallel to the ground when flying.

AMENDMENT: Actually for a bell tetrahedral kite I have found that you do not really need a bridle at all! Just attach the kite line to the front leading corner of the kite directly. Or better still in the middle of the leading cell (which is where the kite books specify). The kite will settle itself into the correct angle for the wind, and becomes much more stable.

Flying the Kite

The kite, like almost all box kites I have seen has a threshold for the wind speed. If wind is below this, kite lists to one side and drops to the ground, refusing to fly at all. If wind is greater than this kite flies well and with good lift, if not height. The angle it flies at depends on where and how it was bridled.

Also becareful in a high wind or the kite will collapse it is only made of drinking straws after all.

Launching the kite is really easy. Just sit the kite, on the rear face with the leading edge facing into the wind. It is one of the few kites that when on the ground like this will stay put. When ready, just pull on the kite line and up it will go.

A single unit of 4 cells I (and others) have found to be highly unstable in any sort of turbulance, prone to doing loops and or crashing into the ground. A 16 cell version (see next) is much more stable and unmoving in the sky and highly recomended, especially as a group project.

Summary

This is my own design and works very well. I have since built tetrahedral kites using 3mm fibreglass spars, plastic tubing, and a sewen covering. And a year later a dowel, 16 cell, flattened version. See the Tetrahedral Kite Plan.

Aside: The main problem with the tetrahedral kites is that you often have 5 to 6 spars all coming together at a single point. If you want the kite to be able to fold flat then the joins become the part with all the problems.

Variations to the basic plan

See also my more complete document on Variations of Tetrahedral Kites

16 Cell Tetrahedral

Make 4, of the kites as above (one packet of 100 straws will be enough), adding a bridle only to one. Tie or clip them together (corner to corner) using fishing clips, split rings, curtain rings, normal string, ribbon, to create a larger 16 cell tetrahedral kite. Attachment is not critical as each individual 4 cell kite is ridged and when tied together into a larger tetrahedral structure that structure is also quite ridged.

The larger kites with more tetrahedra, such as this, seem to fly much better. I have never found a single cell to fly well due to its weight and drag characteristics, though one book tells me that if the single cell is over a meter(!) in size it will also fly well. The larger multi-cell kite seems to stabilize the kite and fly better and higher due to the extra trailing cells.

WARNING: I do not recommend straw kites larger than 16 cells as the kite may start to collapse under its own weight. Straws are not that strong. However maybe a kite using balloon sticks would be better, though I haven't tried. Balloon sticks may be too flexiable for the covering.

Jeff Hittman <jhittman@slip.net> however reported in September 1999, that he built a fully braced 34 cell straw tetra ( 7×3×3 from the Tetra Variations Page ). ``It really has some lift and quite some pull. Looks nice in the sky too.''.

10 or 20 Cell Tetrahedral

Basically instead of forming a tetra which is formed of 2 cells per side make one which is 3 cells per side, creating a 10 cell regular tetrahedron. However I recommend fully bracing each individual cell of the kite.

You can continue to extend the kite in this way to 4 cells per side, forming a 20 cell tetrahedral the same size as the 16 cell above but with the central cavity filled in with 4 more cells.

[photo]

Build a Monster 100 cell tetra

A a class of fourth grade students in Bakersfield, California, made a 100 cell tetrahedral using straws and brightly coloured tissue paper. You can see photos of the final construction and results of this effort clicking on the photo left. Congradulations a job well done.


For these, and many other styles see the Tetra Variations Page .

Responses

For more information about peoples experience with building this tetrahedral kite, and what results they have achieved I suggest you look at the various Responses I have recieved. Many thanks to all who have replied.

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 above and others can read of your results. :-)

Basically the result of this feedback, and my own findings when I built a version (before creating this plan), was that for tetrahedral kites to work they have to be at least 1 meter per side when all the cells are joined or the kite does twirl and be unstable. IE: you really have to create a 16 cell version using this plan.

Other Tetrahedral Kite Plans

This plan was translated into Danish by Thomas Dorf Nielsen. This was however some time ago and this plan has expanded greatly since then.

Another straw tetrahedral kite plan (using tissue paper) and has been made available on the internet by Glenda Woodburn. Another is the Ford Middle School.

You just can't keep a good idea down :-). These plans are fully braced which I recommend for anything larger than a 4 or 16 cell straw tetra. Actually I now recommend fully bracing tetra's if its practical, anyway.

I also recommend you look at the more permanent and robust tetrahedral kite which you can build with dowel or fibreglass spars. (See Tetrahedral Kite Plan).

-- Anthony Thyssen.


Created: 20 September 1995
Updated: 11 July 1997
Author: Anthony Thyssen, <anthony@cit.gu.edu.au>
WWW URL: http://www.cit.gu.edu.au/~anthony/kites/tetra/straw_plan/