----- Original Message -----
From: "Kinney John-r17512" <J.Kinney@freescale.com>
Sent: Monday, January 16, 2006 4:12 PM
Subject: [TowerTalk] Triangular Crank-Up Wind Load Model
>I have a question pertaining to my Hy-Gain HG52SS tower or any other
> tower of this type for that matter. The question: Does anyone have a
> model or has anyone attempted to model the wind loading of this type of
> tower, at heights less than full extension? This tower is rated at 9
> square feet at 50 MPH average wind speed. It would be interesting, to
> me at least, to see a graph or table stating the increase in wind load
> capacity as the tower is lowered to its resting height (21 feet.) I
> asked this question via email directly to Hy-Gain, after their purchase
> by MFJ, but never received a reply.
> Thanks for the bandwidth.
> John Kinney KA7CVJ
I haven't done this analysis, John, but when I posed a similar
question to Karl Tashjian at Tashjian Towers (old Tri-ex), he
told me something surprising. On the Tashjian LM470, the
wind rating actually drops when the antenna is partially nested
because of the way the sections have additional bracing in the
areas where the sections overlap when the tower is fully extended.
So as you lower the tower the wind rating drops for while as the
tower is partially retracted and then come back up to a much
higher value when the tower is fully retracted.
73 de Mike W4EF...................
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