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Wind area of mast.

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Subject: Wind area of mast.
From: fmart@tinet.tinet.fut (EA3KU Fernando Martinez)
Date: Fri, 06 Sep 1996 11:34:57 +0200
> 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.
> Thanks.
> Gene

Hello Gene.

Before to continue, let excuse me for my but english.
I order to anwer your question, you must know that the item you are
looking is named ( on spanish Coeficiente eolico de forma ) Eolic Shape
Coeficient (????? in english . Cilynder shape its vary from 0.6 to 0.8 (
depending on his surface texture ), 0.6 for a very smooth surface ( our
case ) and 0.8 for a very rough surface.
On any case, if your are calcutating the total wind presure over and
antenna system, I think that best rule is to condider the worse case,
its consider the mast as square shape. It will give you a goog safety
factor, then apply the resultant repressure at the top of the mast, then
calculating the 'flector moment' over join point beetween the mast and
the tower ( if you are using a tower ). This, dont increase a lot the
total results and you will have a very good safety factor.


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