Tetrahedral Hints and Tips
Back to Tetrahedral Information
The following is never complete, progress usually achieved by
people mailing me
, which gets me back into
thinking about tetras, and thus adding even more information to these pages.
So the more people mail me with questions, information, or their experiences,
the better the page gets.
General Notes and Problems
Tetrahedral kites are very versatile. There is not just one tetrahedral
kite shape, but an infinite number of shapes and style! Sort of like Lego
blocks but using pyramid shapes. These are explored on my Tetrahedral Variations page.
Tetrahedral being an unusual kite and has as a result unusual problems. 2
of the biggest is weight, and transport. Another is stability in the air.
The bridle point of a tetrahedral is relatively simple. The final
bridal point should be a little forward of the perpendicular from the
spine and the leading point of the kite...
See this diagram I made for a old tetra plan...
The number and actual points to which the bridle attaches to the kite
varies, on the actual kite variation used, but is basically the same
position regardless of model.
For tetrahedral with multiple spines, you add bridle lines to each spine
as you would for a simpler tetrahedral. Actually I find every second spine
enough for 'wide' tetras. You then collect all the front bridle points
together into a single point, along the center line of the kites width.
The bridle lines should be long enough so this point is 2 or so times the
total width of the kite, which prevents too much side on forces from the
bridle likes on the kite itself.
You would do the same with all the rear bridles. Then using a extra set
of line tie the collected front bridles to the rear bridles. The bridle
ring is then added to this connecting line, with its position being the
only adjustment needed is needed to be made to change the angle of the
Look closely at these two photo (click for enlargement) for examples of
this type of bridle line setup...
These extra side-by-side bridle lines also seems to improve the stability
of wide tetrahedral greatly. So much so that often extra side bridles
are added to single spine tetrahedral. For example, this tetra has some
extra side bridles, rather than a rear bridle line attached to the spine.
Because a tetrahedral requires a lot to bracing to generate its pyramid
cell shapes, and that the sails are set at a very high angle compared to
other kites, tetrahedral tend to suffer from weight problems.
A tetra made in the same way a normal kite is made, tends to not even get
off the ground. Then if you do get it up, either it won't stay up, or it
swings wildly from side to side.
In generally if the construction method is too heavy for a small tetra
then it is also too heavy for a large one. Yes there is a slight weight to
sail ratio improvement as a tetra gets larger, but it isn't great.
Fortunately a tetrahedral structure is a space filling structure, and so
very light weight and weak materials can be used to form extremely strong
structures. This is why the tetrahedral structure known as a Octet
Truss is used for making roofs of large convention halls, and is even
as the primary construction method for the new international space
Because of this, tetrahedral are made from ultra light weight materials,
such as straws and bamboo skewers, to form kites that are very large indeed.
No other kite type can really do this.
As a tetrahedral IS a space generating structure, tetrahedral in general
do not easily fold up for storage, or requires lots of fiddling when
putting them together or disassembling. This is why you do not see very
many tetrahedral kites at festivals.
The solutions to this either involve taking the kite almost completely
apart, to store in a long bundle, OR somehow folding them up into a flat
package, which is itself not great for transport.
Alternatively, if each cell is built completely separately, the cells
can be stacked into each other for transport, This produces a very large
bulky stack, but means that on the field you can construct virtually ANY
type of tetrahedral variation you like. (See the Ring
and Rod Construction method below).
A single tetrahedral cell is unstable, 4 cells are only just stable if
made light enough. In general the more cells you have and the lighter the
construction, the more stable a tetrahedral gets!
From personal experience I have found that the wider tetrahedral tend to
fly much more stable. These "wide" shapes allow for multiple bridle lines
which by its nature seem to stabilise the kite. If the kite swings badly,
the extra bridle lines quickly returns the kite to stability.
As such the wide tetra shown at the top of the page, flies extremely stable
and high! Even the 10 cell irregular "keystone" tetra (top left) I have
found to me much more stable than a regular 10 cell "solid" tetrahedral
structure. The main difference, is that three bridle lines are used in
the "keystone" shape, instead of just two for the same sized "solid"
However I have found that if a tetra is light enough and large enough,
they continue to fly stable even when some cells have collapsed and
half the tetra has "pancaked", like a building after an earthquake!.
Cell Construction Methods
The name says it all, each cell has six spars for every edge of the
tetrahedron. It forms a fully braced structure, that is also incredibly
This allows you to use lighter weight spars such as straws, skewers, or
very light dowel. Anything else is just getting too heavy. See the
Building techniques below for more information.
The joints a fully braced cell is where the action really is, and can
consist of "tinker toy" sockets, to string, to plastic tubing and so on.
Just how the joint is constructed also equates to how easily a fully
braced tetra can be transported.
For example if each cell is build completely separate to each other, and
only joined together on the field, then the individual cells can be
stacked into each other. It is still bulky and three dimensional, but a
very large kite will stack into a much smaller volume.
If the joint can fold, then one spar from each cell can be removed (or
folded out of the way, and the kite can fold up accordion like, into a
If all the spars are removable, then you spend a lot of time during setup
and take down on the field, but the kite stored into a not very long
linear bundle, like most other kites. A further advantage is that
individual spars are also then very easy to replace.
This method cuts the number of spars from 6 to 4, shorter spars, and
provides a method of tensioning in the process. Essentially the four
corners of the cell is pushed outward for the center of the cell.
One problem with this is that the center of the leading edge of the cell
tends to get pushed inward, unless a very light weight spar is provided
to stop this, or the edges has a slight inward curve built into them (as
in Cody box kite construction).
The spars however, must be very rigid. As such it is only really suitable
for modern carbon fiber, or epoxy tubing. Also a string or other light
spar is also needed across the back of the cell as part of the tensioning
Transport however is straight forward, either the trailing edge tension is
released, or the center tensioning is released, and each cell will collapse
into a easily transportable bundle of loose sticks and fabric.
Some of the largest (and prettiest) ripstop tetras in the world are built
using this method.
Again to cut down the number of spars only 3 sticks are used. One along
the leading edge and the other along the trailing edge. These are then
pushed apart by a "mast" stick between them.
This has a number of distinct advantages. First the leading edge is
supported, and second both the cross and leading edge spars can extend
across multiple cells! This means that connections between cells can be
extremely rigid, and produce a very strong structure, with only 3 spars
per cell instead of 6.
However strong spars are required to prevent them from breaking from the
side on stressed imposed by the mast. Also 2 of the spars have to be
removed for transport, increasing the setup and take down time involved.
A great web site for viewing this technique is Bell Tetra Info,
and Plan, particularly toward the bottom of the page.
Building Techniques and Styles
Plastic Drinking Straws...
This is extremely popular, straws are light weight, yet very strong.
Tetrahedral kites built with straws tend to fly very high, well and
stable. As they are so cheap and easy to work with they make an excellent
medium for classroom tetra projects.
However straws do not compress very well, tending to fold-up under
stress. As such straw tetrahedral tend to be one time affairs. Due to
this, construction is usually limited to a full cell bracing. That is every
edge of the cell is braced by a straw.
W McClure <firstname.lastname@example.org>, recommends that to strengthen a
very large straw tetras with some long thin dowel along the outside edges
of the tetra. Of course this adds to the weight of the tetra, but can
make the kite last a lot longer than it otherwise normally would.
The straw cells are then covered with either tissue, plastic, or
cellophane (warning: cellophane shrinks!), and then individual cells from
teams of students, or a whole class, are then tied together to form larger
Straws and String...
Joining is usually achieved my threading a light string though the straws
to form individual tetrahedral cells. Generally the ends of the string are
NOT trimmed after the final knots are tied, so that the extra length of
string can be used to tie multiple cells together into larger tetra
For examples see the Tetrahedral Index Page
If you want to fold a straw tetra flat for transport, I have had success
with using hat elastic. in the trailing edges of four cell units. For
more information on this method see... my own straw plan.
The major problem with this technique, is that string such as a nylon
thread, or cotton, which is plenty strong enough, is that it tended to cut
into the drinking straw. Some people recommend superglueing a small
segment of slit straw onto the ends of the bracing straws, to prevent this.
Steve Swindell suggests just touching each straw end to a frying pan, or
other metal plate heats on a stove set to medium or medium-low heat. Touch
the straw to the blade, BARELY pressing down (not much more than the weight
of the straw is needed) for about 1 second.
Wether either method is worth the effort is another matter, and depends on
how much effort you want to put into your straw tetra.
Straws and Hot Glue...
Another technique of building tetrahedral cells with straws however was
pointed out to me by Norm Anderson <email@example.com>. In this case
however he joined the straws with hot melt glue at the joints.
Straws and Balloon Sticks...
Jeff Hittman <firstname.lastname@example.org> has noted to me that balloon sticks
(Plastic sticks used at fairs and festivals to attach balloons to), has
just the right diameter to fit inside a regular drinking straws. He used
2.5 to 3cm segments (about a inch to the Americans) to create the tetra
How he actually used them he did not say. But they could be hot glued into
spiked balls for the straws to slot into, or just superglued glued into
the straw ends to stop the string cutting into the straw.
The master of this techique is TetraLite Kites who sells a book and/or CDrom all about this
technique for just a few dollars. Well worth it.
Essentially you use cheap bamboo skewers sold in your local supermarket
for satay sticks. These are joined together using a very thin walled
plastic tubing from the electronics industry, and cable ties to form the
corner joints. The cells are then covered with Mylar plastic commonly sold
as a silver gift wrapping foil for Christmas presents or for flowers
The result is a very strong but ultra light weight kite using very modern
materials. The kites fly at a very high angle, and very stable. For
transport the trailing stick on every cell has one end "unplugged" and the
whole kite folded up like an accordion into a flat package. Both kites
photoed at the top of this page are of this construction technique.
The bamboo skewers I have found to get brittle with age, and thus most
prone to fracture during landings, or other disasters. I have seen my
tetra completely demolished when a rope from a large Peter Lynn Octopus
whip across a tetrahedral I had sitting on the ground in just the wrong
spot. Only the bridle ring from from that kite was worth the salvage.
Dowel, Carbon Fibre Tubes, Fibreglass...
With these stronger, heaver materials, you can get away from the fully
braced cell structure, using either a mast or corner bracing method
Also if the kite does fly then the inherent strength of the spars will
ensure that very little damage will result due to crashes, landings, or
collisions with other kites and kite lines.
Vinyl plastic tubing from the local hardware, or if you can get them,
specialised hard plastic joints are typically used for construction.
Ring and Rod Construction...
Rob Thomlinson and Tony Broad in England, developed and created a great
web page of building fully braced tetrahedral using a method involving
"screw eye" rings screwed (and glued) into the ends of carbon fiber tubes
(and tube ends reinforced).
The individual cells are then pre-built (any of three different ways) and
stacked into each other for transport. On the flying field the complete
kite is put together in any variation you desire for that days flying
using cable ties to join it all together.
A fantastic solution and extremely versatile.
To see more of this construction technique visit their
How to Make" website. (Offline, link via the Wayback Machine)
Updated: 29 May 2002
Author: Anthony Thyssen,