I'd never try 66' (20 m) of tubing each section 6' (1.8 m) long held
only with hose clamps. That bottom clamp will be holding too much
weight. Short and sweet: if you want that height and you want to be
able to drift off to sleep at night with the wind howling, you are
simply going to have to spend some money. At that height I'd start
looking at sections of aluminum lattice tower from Universal. If you
have to have tubing, I'd get as long and wide diameter as possible,
and shoot bolts through each section (except the top of course) about
2 or 3 feet (.91 m) down from each top so the section above can rest
on something and not be held entirely by friction from a clamp. If I
may put in a "shameless plug," I like doing business with Charlie
Penninger (http://www.penningerradio.com/) who is right here in town
with me, (which solves my problem of getting 24 foot (7.3 m) long
sections) but who will give a fair price on tubing and more important,
will work with customers as an engineer. I just spoke with him on
the phone recently about a 10 foot (3 m) aluminum tube for a roof
mount and he quickly calculated the moment at the top of the mount
where the mast would exit the quad-pod for the wind load at the top of
the mast at a 70 mph (123 kmh) wind. From that he was able to advise
on a sound wall thickness for the diameter I wanted. I think he will
also bring your order to a hamfest he's planning on traveling to if
you wish to pick it up that way. If you have a truck or trailer that
might help you get around the UPS length limit.
One other thing--the W6SAI HF Antenna Handbook has a brief write-up of
a homebrew 160 meter free standing 1/4 w. vertical that was or still
is at K6KBE. It's on page 6-17 of the Orr's handbook. The bottom 88'
(26.8 m) (are a 3 leg, tapering tower with a 12' (3.65 m) face at the
bottom. This is topped off with a 44' (13.4 m) stinger to give a
132' (40.2 m) vertical. This stinger is 2 inches (5 cm) diam. at the
bottom and tapers to .5 inch (12 mm) at the top. It sits two feet (61
cm) into the tower. The tower legs are 4 inch (102 mm) diameter .09
inch (2.5 mm) wall tubing for the bottom half and 3 inch (76 mm)
diameter for the top half.
73
rob / k5uj
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