Geodesic Dome Hubs: Selection, Fabrication, and Structural Fundamentals

Geodesic hubs (connectors) are the critical structural nodes that join struts to form a geodesic dome's triangular framework. Hub selection or fabrication determines the dome's strength, assembly ease, angular precision, and long-term durability.

Hub Function and Importance

Hubs connect 4-6 struts at precise angles (typically 60°, 72°, or combinations) to form the dome's spherical geometry. Each hub transfers loads (dead, live, wind, snow) between struts. Failure at any hub compromises the entire structure. Quality hubs ensure: angular accuracy, load distribution, weather resistance, and assembly repeatability.

Commercial Hub Types

Machined Metal Hubs (Aluminum/Steel): CNC-machined from billet or cast. Precision angles (±0.1°). Threaded or bolted strut attachment. Anodized/galvanized. Highest strength, cost ($15-50/hub). Best for: permanent, large, engineered structures.
Injection-Molded Polymer Hubs: Glass-filled nylon, polypropylene. Molded angles. Bolt/screw attachment. UV-stabilized. Moderate strength, lower cost ($5-15/hub). Best for: greenhouses, temporary, DIY.
Fabricated Plate Hubs: Laser-cut steel/aluminum plates, bent/welded to angles. Customizable. $8-20/hub. Good strength-to-cost.
3D Printed Hubs: PETG, ASA, nylon. Custom geometries. Emerging for prototypes, small domes. Layer adhesion limits structural use.

DIY Hub Fabrication Methods

Conduit/Pipe Connector Method (Classic): Struts = electrical conduit (EMT) or PVC pipe. Hub = central bolt through flattened/crimped strut ends. Steps: flatten ends → drill bolt hole → assemble with washers/nuts. Low cost, proven, adjustable angles. Limitations: bolt loosening, corrosion, angle drift.
Plywood Gusset Plates: 1/2" CDX plywood cut to triangular/hub shapes. Screwed/bolted to struts. Inexpensive, rigid. Interior/dry use only.
Metal Connector Plates: Galvanized steel mending plates, hurricane ties, custom laser-cut. Screwed/bolted. Good for wood struts.

Selection Criteria

Dome Frequency (V): 2V, 3V, 4V, 5V, 6V. Higher V = more struts/hubs, smoother sphere, smaller triangles. Hub count: 2V=26, 3V=46, 4V=76, 5V=122, 6V=162+.
Strut Material: Wood, steel, aluminum, PVC, bamboo. Hub must match attachment method.
Load Requirements: Snow (lb/ft²), wind (mph), live load. Engineering calc for permanent structures.
Assembly Skill/Tools: Machined = wrenches only. DIY = drill, saw, wrenches, jigs.
Budget: Hubs typically 15-30% of frame cost.

Critical Success Factors

• Angular precision: jigs/templates for DIY. Test assemble one pentagon/hexagon first.
• Corrosion protection: galvanize, paint, anodize all ferrous components.
• Foundation: anchor base hubs to footings/deck. Dome lifts in wind without anchorage.
• Cover attachment: separate system (clips, rails, tensioning). Not through hubs.