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

 To: [TowerTalk] Fw: reply (Bencher Skyhawk wind area) SPELUNK.SUENO@prodigy.net (EUGENE SMAR) Mon, 23 Jul 2001 23:07:30 -0400
 ```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 To: bencher To: 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 >To: SPELUNK.SUENO@prodigy.net 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 >>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. >> > List Sponsor: Are you thinking about installing a tower this summer? Call us for information on our fabulous Trylon Titan self-supporting towers - up to 96-feet for less than \$2000! at 888-833-3104 www.ChampionRadio.com ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ```
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