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Re: [TowerTalk] wind load

To: Tower Talk <>
Subject: Re: [TowerTalk] wind load
From: Charles Coldwell <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Thu, 18 Feb 2010 14:37:25 -0500
List-post: <">>
On Thu, Feb 18, 2010 at 1:34 PM, Stan Stockton <> wrote:
> I could be wrong about this but have always thought (from an old Rohn book)
> that 70 MPH equated to 30 pounds per SF of antenna.

OK, so in my example if the maximum wind load at 70 MPH is 15 sq ft,
and we have 30 pounds per square foot, that works out to 450 pounds of
force.  That sounds reasonable.

If we believe the force grows as the wind speed squared, and that a 70
MPH wind puts 30 pounds per square foot of force on the tower (and
that a 0 MPH wind puts 0 pounds), then the constant of proportionality
is 30/4900.  So that means the general formula would be

F = 3/490 * W * W * A

where F is the force in pounds, W is the wind speed in MPH, and A is
the antenna effective cross-sectional area in square feet.

What's the title/author of the Rohn book?

Charles M. Coldwell, W1CMC
"Turn on, log in, tune out"
Winchester, Massachusetts, New England (FN42kk)

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