The objects are
achieved by providing a geodesic structure made of convex-concave elements that
are arranged in an approximate manner, without having to be placed or attached
along predetermined great-circle gridlines. The example of a dome for human
shelter will be used to describe the basic geodesic structure , although it
should be understood that a complete geodesic sphere, a semisphere, or an
irregularly curved structure can also be constructed in a similar manner, and
that geodesic structures constructed according to the invention are not
restricted to a certain size or to certain applications, such as shelter for
humans.
As stated above, the geodesic dome is made of
convex-concave elements that are assembled in an approximate fashion. By
"approximate" is meant that the elements are assembled one next to the
other according to some principle such as overlapping or tangentially touching
adjacent elements, yet randomly in the sense that particular exemplars of the
elements do not necessarily have to be placed or fastened along predetermined
great circle gridlines, nor do they have to be placed in a particular sequence
or at a particular location. In an initial embodiment of the structure ,
identical, shallow, cone-shaped elements, also referred to as "hub
elements," are used as the convex-concave elements and are assembled in an
overlapping configuration, typically from the top of the structure downward,
although a structure could just as well be assembled from the bottom up.
The structure is self-adjusting because the hub
elements are not necessarily precisely spaced from each other, but are, rather,
assembled in an approximate arranged according to some general principle with
virtual struts automatically forming along the single-axis curvature that
extends from vertex to vertex. The geodesic dome thus constructed will have an
overall shape with a curvature that corresponds to an average curvature of all
the hub elements, as will be discussed below. Furthermore, the geodesic dome is
self-triangulated. If lines are drawn from each vertex to adjacent vertexes, one
can see that the entire structure is divided into triangles, albeit triangles of
varying dimensions, including scalene triangles in which each leg of the
triangle is a different length.
Cones were used as the hub elements in a
Preferred Embodiment of the geodesic dome because cones are easier to work with
and less costly than continuously curved elements. Cones can be easily
fabricated from a flat circular sheet of construction material by eliminating a
section of material from the center to the outer edge of the hub, thereby
forming what is hereinafter referred to as an angular deficit in the sheet. This
angular deficit determines the curvature of the hub element, discussed in
greater detail below, and is easily formed either by folding that section of the
material from the vertex to the outer edge or by cutting the section from the
element, and reattaching the cut edges to form the cone. Thus, no machining or
shaping of curved elements is required. The cone shape also imparts improved
strength and rigidity to the material. Thus, materials that are relatively thin
and/or inexpensive can be used to create large spacious enclosures. The elements
can be made of a variety of stiffly flexible materials, including but not
limited to such materials as paperboard, plywood, oriented-strandboard,
cardboard, sheet metal, and sheet plastic or fiberglass material. It is
possible, however, to use several different sizes or shapes of hub elements and
arrange them in an evenly alternating pattern to form the structure. For
example, hub elements of two shapes, i.e., having the same diameter at the outer
perimeter, but having different angular deficits, can be assembled in an
alternating pattern for an aesthetic effect.