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Re: [TowerTalk] Inspect Your Boom to Mast Plates!

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Subject: Re: [TowerTalk] Inspect Your Boom to Mast Plates!
From: "Jim McDonald" <>
Date: Mon, 8 Jan 2007 22:33:39 -0600
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I agree with Bob's advice.

Several years ago, I looked up at my 3L Force-12 EF-340 40M yagi to see the
ends of the boom, where the boom guys were fastened, higher than the center
of the boom at the mast.  Though it was 9 PM, I hastily climbed to inspect
and found the boom-to-mast plate had cracked into seven pieces, each break
through a bolt hole.

I had heard creaking when the wind blew but was in denial as to what it
meant.  I was going to be moving back to AZ soon anyway, so I took the
antenna down the next day.  I replaced the plate with the new, heavy-duty
version when I reinstalled it in AZ, and that one never had a problem.

Jim N7US


-----Original Message-----

I went up the tower yesterday to take down the Christmas
lights and noticed something disturbing.  I happed to notice
that the boom to mast plate (stock 1/4" aluminum plate) on
my KLM 40M4 had stress cracks radiating out from the points
where the four clamps attach the plate to the mast.  The
wind blows a lot here in the Mojave Desert and clearly the
stress of the large yagi has taken it's toll on the plate. 
Fortunately I had planned to take down the beam soon anyway,
hopefully within the next few weeks.  It should last a while
longer but it could have come down the hard way and perhaps
taken out the guys on the way down.  There were no signs of
problems from the ground level and it was easy to overlook
even standing 2' underneath the beam on the tower.

Next time you're up the tower, take a careful and close look
at your boom to mast plates to make sure stress cracks
aren't developing.  This was a first for me.

73, Bob K6ZZ


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