What does the 'frequency' of a dome refer to, and how can I tell which frequency I need?
If you're new to the geodesic world, you're going to find a lot of new terms and terminology that make talking about domes and spheres more specific. 'Frequency' is a simple concept that requires a little bit of analytical thinking, but is very important to understand in order to choose the right dome configuration for your needs.
In common language, 'frequency' refers to the repetition of an occurrence. Since geodesic designs are made up of triangle patterns, recognize that the patterns repeat. Specifically, consider the base triangle pattern that repeats itself over and over as the dome is built. Take a dome with a 10' diameter. In the following frequencies, each larger triangle is the same size, but as the frequency goes up, so does the number of subdivided triangles - which equates to your struts - and the corresponding number of hubs that connect it all together.
Notice that the main triangle is surrounded on all corners by the 5-way hubs.
Given the same thickness of PVC (or whatever material you’re using for the struts), a dome of higher frequency is always stronger than a dome of lower frequency. It is also ‘rounder’, because the angles between triangles are getting smaller.