The recent discussion here about holes and stress risers was brought home
to me yesterday when I noticed that an element had snapped on a Cushcraft
15-4. This is the second element to come off this spring; both broke at
the hole where the U-bolt goes through the one inch diameter tubing. The
good news is that I have procrastinated putting up the big 20 meter antenna
under the 15 meter beam so access is still easy to drop the 15 meter
antenna and rebuild it - I guess with plates and Ubolts. Each of the
broken elements broke when the "official" tv wind numbers were only about
50 mph gusts.
The photos in the ads show that this method of assembly is also used on
the Cushcraft A4, A3, and log periodic antennas - how common is this
failure mechanism - all the talk on the reflector is how to beef up the
40-2CD which does not use this element mounting technique.
Terry Zivney, N4TZ/9
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