Here's one data point:

I've had four unguyed verticals about 32' high in my back yard for over
20 years. They've survived gusts of at least 75 mph in a couple of
storms, but we've never had sustained winds of that level while they've
been up. They're made from 6061-T6 aluminum, 1-1/4, 1-1/8, and 1 inch
diameter. The pieces are 12 feet each, so the overlap is about 2 feet.
For mounting, I drove an 8 foot chain-link fence line post 4 feet into
the ground, then clamped the antenna to it with muffler clamps -- long U
bolts. Some pieces of 1/4" wall PVC pipe sawed lengthwise are used for
insulation.

A 30 foot antenna will have a high angle of radiation -- about 40
degrees above the horizon at maximum -- on 10 meters. A 23 foot antenna
will have a high lobe on 10, but decent radiation at lower angles also.
A few minutes with any antenna modeling program including the free EZNEC
demo program from http://eznec.com and the Vert1 example file will give
you a good idea of what to expect.

Roy Lewallen, W7EL

Ed wrote:
I am considering putting up a ground mounted vertical antenna, based
on using telescopic aluminum tubing such as is available from Texas
Towers or DX Engineering. Tubing available ranges from .500 inch to
2.125" with corresponding increase in price as diameters increase.

My vertical should be limited to a maximum of 30 feet, but preferrably
around 23 - 25 feet. I will feed it with an SGC coupler at the base and
operate 80M - 10M.

My question: Using the 6' long aluminum pieces, what is the minimum
diameter sizes I should start with to enable the antenna stand up to a
75mph wind UN-GUYED. Also, how much "overlap" should I use in the
telescoping pieces?

I will consider alternative means of building the vertical, but I
really wish it to be unguyed .

Any info or recommendations appreciated. TNX

Ed K7AAT