Good Karma Domes - Dome Basics

Definitions

Icosahedron:
a round structure made of 20 equilateral triangles. Each point of a triangle represents some point on an imaginary sphere. (pretty neat Huh?) Each side of the triangle represents a chord of the sphere. Dividing the sides of the equilateral triangle evenly and joining these vertices represents frequency (basic icosahedron is a one frequency). The basic or fundamental equilateral triangle will always be represented by pentagons at vertices, all other vertices will be hexagons.
Strut:
framing member of triangle usually 2x4 or 2x6 representing chord.
Sizes:
sizes of domes are generally accepted or noted by diameter. Example:
30 ft 4 freq. hemisphere refers to 30ft diameter 15 ft high. Since the vertices are on the diameter of the sphere a dome is measured from point to point, and from the outside of the struts.

Frequency

Basically the higher the frequency the more spherical the shape of the dome. and the smaller the triangles. This becomes important when you are 20 feet off the ground with a 20mph wind blowing. An eight foot triangle is easier to manipulate than a sixteen foot triangle. The smaller triangle has a shorter span and will carry more shear stress.

Even-numbered frequencies are perfect sided polygons at hemisphere. In other words all base struts are same length. Conclusion: even-numbered frequency domes will sit flat at hemisphere (neat huh?). Riser walls are all the same height.

A true 5/8 curves back in at bottom. Stem wall is straight, and can be built in triangles or as a conventional wall.


In today's dome market there are two methods of building a dome. Hub-and-strut or Panelized.

Hub-and-strut domes come to your door requiring assembly. Struts or framework is assembled to form skeleton. Then interior framing of triangles. Then decking is fastened. This method requires much labor on scaffolding. And a greater potential for error and accidents.

Good Karma paneled domes come with triangles pre-assembled. Struts or framing material is the best money can buy. Struts and interior framing of triangles are glued and screwed or nailed. Exterior decking (1/2"CDX mill certified unless otherwise specified) is glued and nailed on 6" centers and is factory painted to ensure against rain damage prior to roofing. Triangles or panels come color coded for easy erection. Blue to blue, red to red, stick a bolt in it. Four 3/8" x 4" zinc plated bolts per side; that's 12 bolts per triangle. Our domes exceed building codes and all other manufactured domes.


Advantages of Panel Domes

There is more expertise and knowledge of dome building (as a panel dome builder can build any hub and strut and has taken the time and trial and error to learn a better method. Few hub and strut builders if any have graduated to building panels or I think they would be building them for the following reasons.

  1. 4freq. panel dome 40 feet in dia. with 2x6 and 3/4" plywood about 80lbs. per panel and about 75" long or wide can be set in place by two unskilled laborers from the comfort and safety of scaffolding. One holds and the other puts in bolts. Typical construction time 3 men; one gofer on ground, two men on scaffolding. 40' dia. with 2' riser, hemisphere 2x6 with 3/4" plywood 5 eight hour days. Dome complete and Ready for roofing. I have erected 2x4 -34' dia. with 2' riser by myself in 5 days. panels weigh about 40lbs. One man, One week.
  2. Measurements are exact!!!!! 8' panels ( for 50'dia,) that are cut to a sixteenth of and inch inside and out. You'll think a cabinet maker built your dome. This helps cut down leaks!! Double struts allow for double strength, a full inch and a half for plywood decking on each edge not sharing a single strut that has not been mitered so plywood doesn't sit flat. A full inch and a half for each edge of sheetrock. imagine nailing sheetrock to a single strut, butting two edges over that one strut and then the strut is not mitered so sheetrock doesn't sit flat. You don't have any voids under corners as with a hub system. See drawings below.
  3. Panel domes work quite well for per-insulated. Just make two shells, exterior shell with decking and interior shell just framing; make cavity as wide as you like. Make interior dome out of metal studs cover panels with netting and fill cavity with blown in cellulose or icynene foam.
  4. Safety, SAFETY!!!, safety. Hub and Strut Domes require Climbing around on the outside of the structure (a round frame work) holding with one hand and nailing plywood with the other 20 feet above the ground as the wind blows 20 mph, better not let OSHA see ya!!
  5. Major voids at decking intersections invite or create a clear path for leaks, both water and air.

Why we build Panel Domes

Good Karma Domes fit tight, & voids are eliminated. We glue and nail the plywood decking on at the shop, before the lumber has a chance to warp and twist. In most cases a small amount of caulking at the center and between the struts would make your dome leak-proof. Apply a good roof to your dome and it becomes not just rain-proof but virtually air tight!

Voids also leave little support for exterior & interior decking

Conventional Hub & strut companies leave you to do the decking. A tough job, cutting triangles to fit. A little gap gets progressively worse! Again they are dictating the building process by conventional means. Nailing the decking on after the structure is up. Picture yourself 20' up in the air trying to nail an 8' piece of decking on a round framework.

Our system requires more lumber and labor in the prefabrication phase- But eliminates one major nightmare "The potential of a leaky dome." Decking sits flat on double struts cut to fit at intersections. This system is the one Bucky designed. It realizes the potential strength of the structure and is a lot easier to just bolt and go!


Foundations

This is a pier pattern for a four frequency dome. It is overbuilt! In most areas a 9" pier at every other vertices 3' deep is more than adequate! Check with your local building codes to see what is necessary for your region. Weight loads for your dome come with the kit as does blueprints for concrete piers.


Click on pictures for a larger view.

Useful Math

Pi π
3.1416
Circumference of circle (or perimeter)
Pi*d   or    Pi*2*r where d=diameter   r=radius
Area of circle (or square footage)
Pi*r*r = (πr2)
Area of Sphere (or skin or roofing)
4*Pi*r*r =(4πr2) for hemisphere 2*Pi*r*r = (2πr2)
Volume of Sphere (or interior cubic footage used for calculating HVAC)
4/3 * Pi *r*r*r (4πr3/3)
for hemisphere = 2/3 * Pi *r*r*r = (2πr3/3)
note: by doubling the diameter of a sphere, the surface area is increased by a factor of 4; the volume is increased by a factor of 8
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