[TowerTalk] Verticals of Telescoping Aluminum

[Dana Roode]

Hello,

I've been experimenting with verticals made out of 6063 aluminum tubing,
which telescopes nicely in 1/8" progressive diameters.  I'm interested in any
pointers for determining what combinations of diameters, section lengths, and
guying produce a mechanically sound vertical.  I've been using trial and
error thus far.

The first vertical was made out of 7' sections of 1 1/4" through 5/8"
diameter tubing with 1' section overlaps - 30' tall for 40m.  It works pretty
well.

Now I've built a 62' vertical for 80m.  It has 5 10' sections starting at 1
1/2" diameter at the bottom, and 2 9' sections through 3/4" diameter at the
top.  I use a 1' overlap between sections.

When we were putting it up we had one person telescoping it up and 3 people
manning the guys.  After about 40-50' it was really clear that the weight of
the top of the vertical, along with the flexibility of the tubing in the
middle, could easily make the vertical bend over on itself.  It acted like a
huge noodle, with about that much rigidity.

We decided to try it at 45' for awhile, and its up and well guyed (3 sets),
and seems to be solid.  I'm debating whether to go ahead and slide up the
last two sections, or to start over.  If we are real careful with the guys,
all will be well, but one slip and I've got an upside down U instead of a
vertical.

Any recommendations or experiences to share?  I like the aluminum because I
can telescope it up, no need for any rigging poles, etc.  Should I give up on
it and use another material, or just use larger diameter aluminum?  Is there
a more "scientific" approach to determining the right diameter and lengths
for the vertical sections?

Thanks in advance,

   Dana, K6NR

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com