I am planning to construct a vertical dipole array for 20m. The
electrical calculations are complete (with help from LB Cebik) and now
I'm looking for some advice on the physical construction. I'd like to

Here's one link:

http://k7nv.com/notebook/id3.htm

For 20m (unguyed), the base can be thinner than 1.25". To get an idea,
look at the taper schedule for 20m yagi elements...there the center
section is often 1" or even 7/8".

Torsten
N4OGW