I am building a 28 inch diameter sculpture of a 3v geodesic sphere, I am a sculpture graduate student. i have been doing quite a lot of research and found all of it fascinating and interesting however I am having trouble with some application. I have found all of the lengths for my a,b, and c struts on my sphere, but I am building it out of flat pieces of 3/8" thick birch, and I don''t know specific numbers on how to bevel each side of the triangles to fit, Ive done some playing around, but I''d like to work out a system so i could replicate relatively accurate results by making a jig to cut everything. Basically I have figured out that the bevel angle between the sides of pentagons should be 7 degrees, this seems to fit, but I cant figure out the hexes or for the base sides where the hexes meet the pents and other hexes, any help would be very appreciated from a lowly artist, thanks.

[ Comments 2 ]

posted by
jackinthewoods

19/03/2013 11:11:24

I've discovered that for a 3v Icosa. it's 7 degrees for ALL sides by modelling it in Sketchup thus: (pic attached) althought the plans for the GD62 9 metre psudo 6 (which I've just bought))indicate 6.5 degrees - any comments Paul? what am I missing!!

posted by
Admin

19/03/2013 23:13:45

Hi Jacques, For a standard 3v dome the dihedral angles are 7 degrees for all angles except the ones that join a pentagon base, which is 5.5 degrees. You can see them at the bottom of the 3v tool here: geo-dome.co.uk/3v_tool.asp The plans I sell have been adjusted so all the angles are 6.5 degrees, i did this by changing the height of the hexagon and pentagons from the center points. So the plans are not quite the same as standard 3v geometry. If you are using thin material the difference won''t be critical but as I use frames the angle needs to be within about 0.25 degrees.