In the construction world, we usually talk about stone, concrete, steel, aluminum, and other expensive materials that go into building projects. No one in their right mind would consider building a structure that would surround people with plastic. Well, let’s think about that… the new Boeing 787 Dreamliner uses carbon fiber and other advanced composites – high tech materials that are often bonded with plastics.
The Corvette series from Chevrolet has always used lightweight fiberglass bodies, and there are many new 3-D printed building parts made primarily from polymers that have been melted and laid down layer by layer. So actually, there are examples all around us where we’re surrounded by plastic, and it’s not a bad thing.
Sonostar chose to make it’s domes out of PVC for a lot of reasons. First, the idea was to keep the cost low. PVC pipe is available everywhere in the world, and it’s not expensive. Second, for its strength, it’s lightweight. Third, it’s flexible. Fourth, it comes in a lot of different sizes, and fifth, it comes in a lot of different colors.
As important as the first one is (cost and availability), the second and third are equally critical. Schedule 40 PVC was designed to be used for high pressure liquid and air lines, so there is a standard that is universal and consistent. The way it is made, you just don’t get pieces that are less strong than others. Compared to wood or bamboo, it is superior in tensile strength. The biggest difference, however is in its flexibility. The reason it works so well with geodesic domes is in the angles that it must conform to. With metal, there is no flexibility, so you must cut the struts very precisely, and the angles where they fit into the hubs must be accurate to within one degree. Within a geodesic dome, there are varying angles depending on the strut length and frequency, and from a mathematical standpoint, it is impossible to have any one hub fit all the angles needed. The standard Sonostar hubs have 10 degrees molded into each arm of the ½” hubs, and 12 degrees molded into the megahubs’ arms. This helps a lot with creating the overall curvature of the dome, but in some domes, the same hubs have to accommodate 7 degrees in some angles and over 15 degrees in others. Only a material with flexibility similar to PVC pipe can do that.
There are many situations where only metal is acceptable. However, for the vast majority of dome projects, PVC is both economical and practical. Sonostar uses PVC because it is the most economical, most flexible, most available, and most cost-effective material in the world for the specific purpose of building domes. When you build a Sonostar dome, you’re taking advantage of both timeless mathematical formulas and leading-edge technology.