Next year I would like to refine it by replacing the swimming pool poles
with aluminum tubing (6 foot sections) where each section fits into the
previous one. Figure I will need 6 sections to allow for 4 inches inserts.
Then hose clamp them. May have to double up and use double wall tubing.

Another alternative: I've been told that it's easy to purchase
sections of aluminum tubing with built-in snap-together fittings.
They're sold in the concrete/cement portion of building-supply stores,
and are used to create the long handles for concrete "floating"
(smoothing) tools.

I picked up a half-dozen poles like this at a local surplus-metals
dealer. They'd make a very decent mast, and probably a decent
vertical (although I'm not sure just how reliable an electrical
contact exists between adjacent sections when they're snapped
together). They're 1" in diameter and have an overlap area of about
2".

Trying to figure what diameter to start with at the bottom. Greatly prefer
NOT to use guy wires.

I'd encourage you to always use at least one set of guys on an
impromptu vertical of this size. It really wouldn't take all that
much wind force at the top to render your tripod unstable... and
having a 32-foot aluminum pole come down on somebody's head would
really spoil your Field Day.

Another problem is insulating the 32 foot radiator from the tripod. Maybe a
5 foot section of plastic pipe PVC ???

Sure, that'd work. PVC cap on the bottom, notch out a spot a couple
of inches above the bottom to run a cable-and-clamp through, and you'd
be good to go.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!