TT:
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-----
From: EUGENE SMAR <SPELUNK.SUENO@prodigy.net>
To: bencher <bencher@ameritech.net>
To: <towertalk@contesting.com>
Date: Tuesday, June 19, 2001 6:23 PM
Subject: Re: reply
>I appreciate your response. Thanks for going through the trouble.
However,
>I still don't understand HOW you calculate the 8.5 sqft. How did you
arrive
>at that figure, and not 7.2 sqft or 10.6 sqft (to pull random figures out
of
>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
force
>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 <bencher@ameritech.net>
>To: SPELUNK.SUENO@prodigy.net <SPELUNK.SUENO@prodigy.net>
To: <towertalk@contesting.com>
>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
>>do.
>>Your calculations are correct in the sense that that is the surface
>>square
>>footage. But since at any angle of view a good part of the antenna is
>>shielded
>>by other portions of the antenna that is not the usual way of measuring
>>wind
>>load area. In fact the amount of surface presented to the wind never
>>exceeds
>>about 8.5 square feet.
>>
>>OK?
>>
>>73
>>
>>Bencher, Inc.
>>
>
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