Over Thanksgiving break, I built a 9-ft diameter geodesic dome in my backyard. The overall cost of the materials was less than $300 (not counting furnishing). It was a great project to learn more about dome design, build something hands-on, and develop appreciation for the elegance of Platonic polyhedra!

I. Research

Summary: Geodesic domes are based on creating structures in the shape of spheres but using flat triangular pieces. They are light but sturdier than other spheres in terms of weight bearing capacity. To start off by projecting triangles onto a spherical surface, you use Platonic polyhedra inscribed into a sphere, and then subdivide all of the surfaces into smaller triangles using triangulation and three classes of geodesic dividing.

• Geodesic domes = spherical structures formed by triangular building blocks ⇒ light yet sturdy; inscribed polyhedra can be octahedron or icosahedron

• Invented by Bauersfeld for planetarium, then Fuller who coined "geodesic dome" and created Biosphere

  • If geodesic dome bearing capacity is 100%, Lamella is 75%, spiral-latitudinal dome is 50%, and Schwedler dome is 30%

• Split a sphere into easier to construct flat triangles; starting point is to use Platonic polyhedra (ex. octahedron or icosahedron) inscribed in a sphere

  • Then use geodesic division of polyhedron's faces into smaller triangles (3 classes)

  

  • Need to project 1D triangle vertices onto surface of a sphere

    • Use spherical coords w azimuthal and zenith distance of vertices; use cartesian ⇒ polar

    

    

    My sketches:

    

II. 3D Model/Calculations

I created a 2 frequency geodesic dome and 3D printed a miniature model out of PLA using a Creality Ender 3 Pro printer. A geodesic dome requires 10 AAA triangles and 30 BAB isosceles triangles (in total 35 A struts and 30 B struts).

source: Zip Tie Domes

2v geodome calculator: https://www.ziptiedomes.com/geodesic-dome-calculators/2v-geodesic-dome-calculator.htm

III. Materials and Building

Materials

I cut the 1/2” PVC into 35 A struts of 2’ 7” and 30 B struts of 2’ 3”. For the hubs, I cut around 2” thick sections from the 4” drain pipe. Instead of drilling holes in the hubs to intersect the struts, I maintained flexibility in the bend angles by directly ziptieing them onto the outside of the hubs, creating additional degrees of freedom.

To prevent the hubs from wearing down the plastic tarp, I used sealant and plastic plates to put an outer covering on the hubs. I then zip tied the dome to a floor tarp, secured the floor tarp using ropes and stakes, and used Gorilla tape to make the transparent covering secure and waterproof.

IV. Furnishing

I added 2 bean bags, a blanket, a table, and some camping tent lights. :)

Knowing that I am capable of taking a project from idea to execution gives me a sense of awe that I could literally do this for anything. There’s a sense of creative power in knowing that whatever I want to build, I could learn it, even if it takes years and talking to people much much smarter than me who know how to do it, and figure out a way to turn it into reality.