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Wind area of mast.

To: <>
Subject: Wind area of mast.
From: (Stan Griffiths)
Date: Fri, 13 Sep 1996 03:54:52 -0700 (PDT)
>I want to calculate the effective wind area of
>a 2" diameter mast that is 72" long.
>Therefore 72" X 2" = 144 = 1 sq.ft.
>The calculation above would be accurate if the
>mast were square.  But because it's round
>isn't there a constant I neet to multiply the
>result by.
>If anyone know this constant please let me know
>and also tell me its source such as EIA-222, etc.

Hi Gene,

I think the number is 2/3, but I don't know the origin of it.

One caution when using this factor to reduce the area of round members.  I
noticed that there are TWO figures for wind loading capability in the
current Rohn Catalog shown on the guying charts.  One figure is for flat
members and the other figure, a larger one, is shown for round members.  So
I think Rohn is already taking the shape of the antenna load into
consideration in publishing two numbers for wind loading.  I think it would
be incorrect for you to use Rohn's wind loading number for round members and
then also reduce the area of your antenna and mast by 2/3.  I believe this
amounts to using the same factor twice when it should only be used once.

Any other ideas on this . . . ?


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