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[TowerTalk] Fw: reply (Bencher Skyhawk wind area)

To: <>
Subject: [TowerTalk] Fw: reply (Bencher Skyhawk wind area)
Date: Mon, 23 Jul 2001 23:07:30 -0400

     Here is Bencher's reply to my query about whether I correctly
calculated the wind area of their Skyhawk tribander (I calculated 12+ sqft
of element area alone, and their specs say 8.5 sqft.)  Also included is my
response to their reply (?).  I needed further clarification (and maybe you
will, too) on HOW they figured out the aea.

     I waited until today for their second reply.  Not here yet.

73 de
Gene Smar  AD3F
-----Original Message-----
To: bencher <>
To: <>
Date: Tuesday, June 19, 2001 6:23 PM
Subject: Re: reply

>I appreciate your response.  Thanks for going through the trouble.
>I still don't understand HOW you calculate the 8.5 sqft.  How did you
>at that figure, and not 7.2 sqft or 10.6 sqft (to pull random figures out
>the air as examples.)  Does this figure account for turbulence of the
>windstream behind an element (the shielding you mentioned in your reply)?
>What I want to do is determine, via aerodynamic calculations, the wind
>exerted by an 85 mph wind on the Skyhawk at the worst-case orientation (and
>what IS that orientation?)  The equations I've found go something like the
>following:  F = CAP, where C = 1.2 for long, thin tubular structures like
>Yagi elements, A = rectangular projected area (shadow area) of the elements
>(length X diameter for each segment), and P = wind pressure (psf) = 0.00256
>X V ^2(mph) X sin^2 (Angle of element to wind direction).  This is from a
>1960's aerodynamic engineering text.
>Can you provide more detail on the 8.5 sqft?  Thanks again.
>73 de
>Gene Smar  AD3F
>-----Original Message-----
>From: bencher <>
>To: <>
To: <>
>Date: Tuesday, June 19, 2001 2:11 PM
>Subject: reply
>>Well, it's right - and it's wrong, depending on what you are trying to
>>Your calculations are correct in the sense that that is the surface
>>footage. But since at any angle of view a good part of the antenna is
>>by other portions of the antenna that is not the usual way of measuring
>>load area. In fact the amount of surface presented to the wind never
>>about 8.5 square feet.
>>Bencher, Inc.

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