Tetrahedral Kite using Straws

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Index

• Other Tetrahedral Plans
• What is a Tetrahedral Kite!
• Requirements
• Construction
• Flying the Kite
• Summary
• Variations to the basic plan
• Peoples Responses (Separate Document)

A Video on making a straw tetrahedral is available at
10 Play: DIY Science: Kite making, Sat 11 Mar 2017

Glenda Woodburg's Straw Tetrahedral (Offline, link via the Wayback Machine)

A Glenda Woodburg Copy (Non-english)

Ford Middle School Straw Tetrahedral (Offline, link via the Wayback Machine)

Kites Tetrahedron, a k12 classroom project (Offline, link via the Wayback Machine)

Kansas City Tetrahedron (Offline, link via the Wayback Machine)

You just can't keep a good idea down :-).

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

• Spars: about 25 drinking straws per 4 cell kite (with spares).
  A packet of 100 party straws is enough for 4 such, four cell kites. (which joined together creates a 16 cell version - recomended).
• Joining: Very light weight multi-filament nylon (twisted is fine), or Sewing Cotton. Nylon kite line is better as it is springy under load. Monofilament fishing line is not any good as it cuts the straws and it is difficult to tie knots in it (tangles yes - tie knots no :-). Thick Sewing thread, or light string, can be used in a pinch.
• The lightest grade hat elastic which you can find (about two straws in length per kite). It's actualy optional.
• Covering: thin polythene (shopping bags), or wrapping paper (mylar foil), Or even, the ultra thin freezer bags or tissue paper. Basically any light weight cover (much lighter than plain paper) should work fine..
• A bit of fuse or telephone wire, twice as long as the straws, for threading the thread and hat elastic.

Step 1.

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, which isn't wanted.

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.

Step 3.

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.

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.

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.

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.

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.

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

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

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

16 Cell Tetrahedral

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

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.

Build a Monster 100 cell tetra

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

Responses

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.

-- Anthony Thyssen.