Rob,
I would totally agree with you as far as not using hose clamps (especially
on the bottom) of a 66 ft vertical. However, I will disagree with you
needing alum lattice tower. I constructed a 80 mtr 4 sq array using alum
tubing of which the bottom 19 ft is 2 1/2" tubing.
I do have them guyed in three spots (first at 19 ft). I do not use any hose
clamps at all. As you suggested, I use 1/4" bolts for about half of the
height, and then rivits for the rest.
I know they have survived winds in excess of 60mph (which are not at all
uncommon at my QTH), since I reset my weather station in Jan, the highest
gust so far this year was 54 back on 17 Feb.
Two years ago in the summer we had winds peaking at 74mph; I didn't have
the 80M 4 sq up at the time, but I did have my two Force 12 Mag 160VX's up
and they survived with no problems. They are 60 ft lenear loaded verticals
for 160M and have only one set of guys (the first 12 ft use 3" tubing and
the 2 3/4 for the next11+ ft.
Dick K8ZTT
----- Original Message -----
From: "Rob Atkinson" <ranchorobbo@gmail.com>
To: <towertalk@contesting.com>
Sent: Saturday, March 14, 2009 3:45 PM
Subject: Re: [TowerTalk] 66-Foot (20.1 meter) Vertical (overlap of tubing)
> 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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