Introduction to Hexagonal Geodesic Domes
Most conventional geodesic domes are based on a triangular
tesselation. They are "high frequency" variants of an
However, this is not how nature builds apparatus such as
the eyes of flies:
Also, it's not what Haekel's drawings of radiolaria showed:
One reason for that is that - while triangles are very
strong - sheets constructed from them are very wasteful of
The most efficient structure to use to tesselate into a
two-dimensional spaces is usually hexagonal.
Soccer balls illustrate the layout of hexagonal domes. The
resulting polyhedra are known as "duals" of the polyhedra of
conventional geodesic domes.
However, such domes are not very common.
One possible reason for that is that the most basic
hexagonal dome structure is not stable.
The following photograph shows such a structure suspended
from one node - to illustrate the nature of the problem:
Hexagonal geodesic domes
Stable domes with hexagonal structural elements can
be constructed - provided they can utilise
additional sources of structural support.
In fact, a number of large hexagonal domes have been
The Montreal dome:
This dome illustrates the simplest dual-layer tetrahedral-truss design.
The Eden Project domes:
The Eden Project domes utilise an unusual tetrahedral-truss
- which requires relatively little additional material and
results in a remarkably thin dome.
This configuration is also reasonably stable - though it has
some stability issues when compared to structures which use
more material - such as the Montreal dome.
There are many more physical hexagonal domes at the top of this
site's links section.
Many hexagonal domes tend to divide their struts into two categories:
- Large, strong struts form the hexagonal shell:
- These struts provide the primary weight-bearing support for the dome.
- Truss struts are narrower and lighter:
- These struts provide stability for the dome.
This site explores the possibilities for stabilising
There are essentially two main sorts of approach:
Roughly the same topologies are availble to both approaches.
- Use supporting struts;
- Use tension elements.
This simulates the physics of mass-compression-tension
structures - and allows them to be manipulated interactively
in real time from within a browser window.
Using supporting struts
Most of the existing hexagonal geodesic domes use supporting
Conventionally, structures containing tension elements which
are necessary to their structural integrity are known as
Using tensegrity has a number of attractions - in particular
the resulting structures can be stable and strong - but are
also light, cheap and resiliant.
A simple tensegrity is pictured here:
Domes have been constructed in the past using the principles
of tensegrity. However they have tended to offer an
external surface which consists of tension elements.
Having external tension elements may be acceptable when
throwing a tarpaulin over the resulting dome - but presents
some challenges when more conventional roofing approached
This site offers a new aproach to stabilising domes based on
an external structural shell consisting of a hexagon-pentagon
tesselation - using the principles of tensegrity.
The following photograph shows a chopstick dodecahedron
reinforced using a single layer of string:
The structure deforms negligibly under its own weight.
Also, it easily supports its own weight.
The idea of using tension elements to replace stabilising
struts - takes the natural split into two types of
structural material often found in hexagonal domes to an
The stabilising components do not need to support
compressive forces to do their job effectively. Use of
tension elements can have cost and weight advantages - since
breaking strains are often dramatically higher than
buckling stresses in materials of equivalent weight or cost.
For more details about this,
see the simulation page.
The weight loss caused by eliminating unnecessary
compression elements (and replacing them with tension
elements) can be significant.
Converting a conventional triangular geodesic dome into a
hexagonal dome containing the same volume constits of
eliminating two thirds of the struts - and about
a third of the hubs.
Most of the struts in a conventional geodesic dome are
pretty redundant - and are not really necessary for the
structure to retain its structural integrity.
Also, triangular regions present some problems when roofing
- due to problems in the corners of the triangles. These
are stressed regions - and are also points of reduced
strength. Replacing the triangles with hexagons neatly
solves this problem.
Hexagonal domes also distribute strength more evenly over
their surfaces - strength of triangular domes is
concentrated more at their hubs. Hexagonal domes do not
have such heavy concentrations of structural material at
When is using this sort of structure appropriate?
The answer to that is simple: when building large
Small domes do not have significant difficulties supporting
their own weight. Component costs are also very significant
(compared to labour costs).
However weight becomes increasing significant as the size of
the dome increases - until it is a heavily dominant factor.
Because domes built using strong weight-bearing components
and lighter stabilising components can be made significantly
lighter than conventional geodesic domes, they can be made
The principle of using the minimum quantity of weight-
bearing materials (and using more lightweight materials to
provide stability) becomes increasingly important as the
size of the dome increases.
With a small dome hexagonal geometry and multiple layers are
a complication - in very large domes they are practically a
Large domes tend to need thicker shells - and thus require
Many such hexagonal domes have been constructed.
In theory more thickness than is provided by two layers
may be needed for very large domes. The most obvious
approach under such circumstances would be to add more layers.
Domes with more than one hexagonal layer have been constructed -
see the sections devoted to the ASM dome and the Climatron in
our links section.
The hexagonal layers would be weight-bearing, the triangular layers
stabilising - with everything connected by tetrahedra.