DIY Geodesic Dome that packs into a suitcase

Model of the geodesic hemispherical dome, 4-frequency icosahedron.

The universal joint using off-the-peg materials.

Unpacking the struts and ties from the boot of the car.

Fixing the cladding to the space frame was as easy as hanging a curtain!

Curtain rods (springs) prestressed the cladding.

Interior view of the parachute shelter. The principles of ancient kite technology applied to a contemporary tent.

An instant temporary private Eden on a camping site in the south of France in 1972.

Reminiscent of the iconic photo - Earthrise - taken by Apollo 8 astronaut in 1968.

Curiosity and the pleasure of finding things out motivated this project.

In order to understand the geometry of geodesic domes and to get a good feel for its structural behaviour, one must build one!

There are two major design problems: connector and cladding.

Connector

Looking into the published images on connectors for geodesic domes, I could not find a really simple joint suitable for DIY.

Starting with the knowledge that in a triangulated frame the connector can be a ‘pin-joint’ (hinge) as it is primarily subjected to axial forces (compression or tension) – no bending!  The Eureka moment came while I was playing in the workshop joining bits of wood and metal. The universal joint (see Figure 2) takes advantage of the bendability, strength and durability of metal.. With this connector there is no need to calculate the axial angles of the struts and ties. By tightening the nut of a long bolt  the metal strips, and the ends of the members, will bend to the correct axial angle.

Struts and Ties Lengths

I wanted my dome to be a hemisphere and without dissecting the triangles at its equator. The lengths of the struts and ties should not exceed 1 metre. A 4-frequency icosahedron met this brief. The chord factors (length of members) were simply worked out using the appropriate table (Dome Book 2, published by Pacific Domes, 1971). For this 6 metre diameter geodesic dome I used birch dowels 18mm dia.

Required:

1. 93.50 cm. 30 members
2. 90.00 cm. 70 members
3. 85.90 cm. 30 members
4. 80.00 cm. 30 members
5. 84.75 cm. 60 members
6. 72.85 cm. 30 members

Total: 250

Note the very high 52/1 slenderness ratio (length divided by diameter) of the struts.

Cladding

To clad a doubly curved surface with prefabricated materials and to make it watertight is a challenge.

For my experimental, lightweight, demountable shelter I chose a parachute (price £4.50, 1971). It is dome shaped and fits loosely inside the 6 metre diameter dome. Curtain rods (springs) fixed the parachute to the joints of the dome, thus prestressing the fabric.

Erection

For the location of my experimental shelter I chose a camping site in the hills near Roquebrune-Cap-Martin on the easterly end of the Cote d’Azur (not far from the ‘hostel’ where Le Corbusier spent the summers and where he dies of a heart attack while swimming in 1965). A slightly sloping spot in a wooded area was ideal.

The assembly of my prefabricated ultra-lightweight geodesic dome resembled the ‘growth’ of cells, expanding in a centrifugal nature. The ends of the struts and ties had a colour code.

I began by assembling a triangulated pentagon on the ground, next adding 5 triangulated hexagons each sharing 1 edge with the former. A shallow dome began to form. I supported this structure on a stool in order to lift it off the ground. Adding 5 more triangulated hexagons, each sharing 2 edges with the above. Next adding 5 triangulated half-hexagons, each sharing 3 edges with the above, thus completing the top part ½ of the 4-frequency icosahedron dome.

The 5-fold symmetry of this structure dictated where the rest of the various lengths of struts and ties should go, making sure, at every stage, that the colour coded ends of the members did match. It took me about 2 hours to erect the dome single-handed.

Fixing the parachute to the space frame was easy and quick, like hanging a curtain! It was exciting to experience how this spherical double layer prestressed system increased the rigidity of the whole structure – synergy.

This project was first published in AD (Architectural Design) 02.1973.

Lighter than Air!

Having read that the geodesic domes (Biomes) at the Eden Project in Cornwall weigh less than the volume of air they enclose, I thought to check whether this is also true with my small geodesic dome?

1.2 kg (density of air per cubic metre) x 56.5 (volume of air enclosed by hemispherical dome, 6 metre diameter) = 67.8 kg.

Weight of the structure + cladding: 38 kg (struts and ties) + 3 kg (parachute) = 41 kg!

Space Frame Trellises

My new and original plant support system was inspired by Buckminster Fuller (1895-1983), the inventor of the geodesic dome. The key feature of the SFT system is its variability, which is made easy with my deceptively simple universal connector.

Form
The structural shapes of the SFT are modelled on molecules. Why look at molecules? – Nature is always the sublime teacher of structural economy.

Lawrence Bragg pioneered in 1912 the x-ray diffraction technique to ‘see’ the three-dimensional arrangement of individual atoms in crystals. The conjecture by a few scientists that graphite-like sheets (hexagonal lattices) could be bent into geodesic structures was indeed confirmed. These carbon-cage molecules, which form very stable structures, are referred to as ‘fullerenes’ in honour of Buckminster Fuller who first explored and applied these geodesic structures in his architectural designs.

A geodesic is the shortest curve between two points on a curved surfaces laying wholly on the surface. We find geodesic patterns in very different things and very different orders of magnitude and in many disguises. They are present in:

• Fullerenes
• Double helix of DNA
• Protein shells of viruses
• Pollen grains
• Skeletons of various tiny marine organisms
• Shapes of various species of fungi
• Compound eyes in various species of insects
• Conical helices in various species of shells and horns of animals
• Muscular fibres, for example the circular and longitudinal muscles of the mammalian heart
• Helical twists in many climbing plants

Geodesic space frame structures are efficient regardless of scale.
What is a space frame? – A three-dimensional frame, usually triangulated in all directions, composed of struts and ties interconnected so that they all share in carrying any load.

Application
Trellises are used as obelisks, screens, arches, arbours and pergolas. Trellises have a particular relevance to today’s smaller gardens and ‘gardens in the sky‘. Obelisks and arches can be used to frame a view, define an entrance or path. Obelisks can give instant height to a border. An arbour can partly hide a sitting area.

Trellised walks are surely among the most delightful features in the garden. Their use goes back to antiquity. Imaginative trellises can also be used as sculptures in the garden. Generally, trellises have a rustic appearance and are heavy in every sense, physically and aesthetically. The structural form of 21st century trellises should be minimal, lightweight and almost invisible!

My SFT system, analogous to a Meccano kit, can be used in a new garden project and also to rejuvenate an existing area of the garden. A unique feature of my SFT system is that individual struts can be threaded through the branches of an established plant and assembled into a very strong and unobtrusive trellis.

Cost
My space frame trellises are inexpensive to make as they use standard off the peg materials. They can be fabricated by any blacksmith or any DIY enthusiast.

Geodesic Dome

A fourfold symmetry adaptable to plans with right angles, which is the norm.

Geodesic Dome

Geodesic Dome