[TowerTalk] Guying Alum Tower
john at kk9a.com
john at kk9a.com
Tue Dec 8 06:47:06 EST 2015
Well stated Jim. I have used guys on aluminum towers. I believe that it
made the structure stronger and it certainly made it more comfortable to
climb. The Universal Tower catalog shows their tower with guys (at least
it used to) but it offers no guidance on doing this.
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Guying Alum Tower
From: K6OK via TowerTalk <towertalk at contesting.com>
Reply-to: K6OK <jvarn359 at googlemail.com>
Date: Mon, 7 Dec 2015 17:13:33 -0800
Rick N6RK is right on the money, there can be a significant benefit in
guying aluminum towers that were originally sold as standalone towers. In
fact, aluminum towers benefit from guying more than steel towers do. This
is because aluminum is 3x more elastic than steel, causing the tower to
bend more away from the vertical in the wind (P-delta effect). The more a
tower bends, P-delta grows, leaving less capacity available for antennas.
Guy wires help keep the tower vertical, reducing P-delta, allowing more
capacity for antennas.
But guying aluminum towers should not be done by rule of thumb or seat of
the pants. To ensure success an engineering analysis by a PE is needed.
Aluminum towers are finicky. Every place where the Z-brace is welded to the
legs, there is a "heat affected zone" near each weld where the yield
strength drops from 35ksi to 15ksi (assuming 6061-T6). Placement of guy
wire attachment points, both the height above ground and relative to the
welds, are critical. Stresses at every weld zone need to be checked.
73 Jim K6OK
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