Advanced Geodesic Dome Question

This summer I plan on building an elliptical geodesic dome.

I based it off an octahedron frequency 5. I stretched my face triangle so that the corners all matched up with a 20 by 30 ellipse. I then projected lines from the center to every intersection on my face triangle.

I used spherical coordinates to find all my points, built an excel spreadsheet to calculate strut lengths, central angles, plotted them in AutoCAD......DOME.

See picture:
www.lostmachine.com/images/m...pdome.jpg

Here is my Question.

When I kept the divisions on my equilateral triangle proportionally correct while I manipulated it to fit into the ellipsoid the projections give huge differences in Strut length, varying from 2.5’ in the corners to over 6’ in the middle.

The engineer in me says that if my strut lengths were closer to the same length I’d have a stronger dome. I look at my face triangle and I think I could shrink the triangles near the center and that would help when I do my projection...

So, what is the best way to go about this?

Should I feel responsible for coming up with a relationship for the projected strut lengths and that of the face triangle and then manipulate accordantly?

Is there any written material covering this problem?

I know if I have all my struts the same length, I end up with all my points on a plane. I want to keep the same general curvature but would like more uniform struts.

I’m tempted to simply estimate, pull the inner triangles in and recalculate.

Then there is my other question.

If I do this, is it going to mess with the dome's ability to transfer forces throughout the structure? Is my gain in strength from shorter strut lengths going to be negated by odd angles?


Here is a link to the AutoCAD drawings in you would like to see them.

www.lostmachine.com/images/m...tower.dwg


Thanks for the Help.

LM

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