Anyone planning to build a geodesic dome will want to look at the image below. It identifies how many struts used for different frequencies. The higher the frequency, the more struts are used, and the stronger the geodesic dome will be.
Note: odd frequency domes can be more or less than 1/2 of a sphere. This affects the number of struts used. Shown above are a 3v 5/9 and a 5v 8/15. For a more detailed chart click here.
The obvious question
So why not always build domes with the same frequency? Three factors: strength, simplicity and cost.
The most popular frequency is the 3v because it uses less struts than a 4v which makes it easier, faster, and less expensive to build, but if you want a geodesic dome larger than 30 feet (9m) in diameter, traditional materials will not be strong enough. You then have 2 options:
- Use better and stronger materials
- Increase the frequency of your geodesic dome
And this is how many people come to consider a different frequency.
Odd and Even frequencies
Even frequencies such as 2v, 4v, 6v and so forth can “split”(truncate) a sphere at the center (making it a hemisphere) and create a dome which is flat at its base. This is the frequency most often used in the domes you see.
Odd frequencies such as 1v, 3v,5v do not naturally truncate at the center of a sphere, and they are not flat at their base.
But there is an exception to odd frequencies. The Kruschke method or geometry is different than the traditional method 1 geometry (what most use). With it you can calculate a geodesic dome which will be flat at its base for odd frequencies. Domerama has 3v Kruschke calculators in the Calculators section.