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 ```Jim: AAAARRRRRGH! DON'T use 0.66! It's WRONG! You'll underestimate the wind load of your array. The number you're mentioning is the ratio between the shape factors for long, cylindrical (= 1.2) vs flat (= 2.0) shapes for wind pressure on a structural member. (Divide the two numbers and you get 0.6, but notice that the shape factor for long cylindrical shapes is, nevertheless, greater than 1.0) I brought up this same subject last summer and learned that my assumptions in windload design, e.g., 0.66 shape factor, were erroneous. Check out the archives ca. June 10, 2001 for a lengthy thread or two on the subject. BTW - the net force on your EME booms will be at right angles to the boom, NOT in line with the wind. The magnitude will be Cos^2 of angle, so the force drops off rapidly as you turn the boom into the wind. (Don't argue with me, argue with Gustav Eiffel.) Happy reading. 73 de Gene Smar AD3F -----Original Message----- From: WB9UWA Jim Shaffer To: towertalk@contesting.com To: Date: Saturday, February 16, 2002 6:18 PM Subject: [TowerTalk] Array windload calculation. > >Hi All, > >I am designing my next EME array and had some question about calculating >windloading. >The array will be primarily round tubing so I am applying a .66 correction >factor to >show the round tubing offering less wind resistance then a flat surface. The >problem I come >up with when calculating horizontal tubing is what to do about orientation >to the wind? >Obviously the windload will change depending on wind direction. What is the >proper >fudge factor here? > >73, Jim Shaffer, WB9UWA. > > >________________________________________________________________________ >Where do you get ICE bandpass filters & beverage matching boxes? The >same place that pays for the hosting of this list: The eHam Store. >Order online at http://store.eham.net. >----------------------------------------------------------------------- > >----- >FAQ on WWW: http://www.contesting.com/FAQ/towertalk >Submissions: towertalk@contesting.com >Administrative requests: towertalk-REQUEST@contesting.com >Problems: owner-towertalk@contesting.com > ________________________________________________________________________ Where do you get ICE bandpass filters & beverage matching boxes? The same place that pays for the hosting of this list: The eHam Store. Order online at http://store.eham.net. ----------------------------------------------------------------------- ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ```