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Re: analysis of multi-sided, tapered, steel tubes/pipe

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In the absence of better information, I would be conservative and the
greater drag coefficient, not the smaller one.

-----Original Message-----
From: Vinson, Brian <BrianV(--nospam--at)>
To: 'seaint(--nospam--at)' <seaint(--nospam--at)>
Date: Friday, February 12, 1999 10:31 AM
Subject: analysis of multi-sided, tapered, steel tubes/pipe

>I work for Valmont Industries and we have been recently been faced with the
>of how to analyze 18-sided tapered poles.  We have been designing 8,12, and
>16 sided
>poles using recommendations in the EIA/TIA code for drag/force
>The code does
>not however give a value for 18 sided poles.  Values for the different pole
>types are as follows.
>8 sided = 1.20
>12 sided = 1.03 ===> 16.5% lower than 8 sided
>16 sided = 0.72 ===> 43% lower than 12 sided
>18 sided = ?  =====> Does anyone have a recommendation of what to use or
>where I can find some supporting documentation?
>Round = 0.59 =====> only 22% lower than 16 sided
>It seems to me that I could make some kind of correlation between the # of
>sides for each type of
>pole and the force coefficients.  After all, the difference is not that
>between 16 sided and round anyway.
>Would anyone say it to be unethical for me to use 0.59 for the 18 sided
>Brian Vinson, EIT