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## [Towertalk] Wind pressure calculations (2/3 factor)

 To: [Towertalk] Wind pressure calculations (2/3 factor) richard@karlquist.com (Richard Karlquist) Wed, 27 Feb 2002 17:00:58 -0800
 ```Here is a quote from the YS manual: > it calculates the wind load on each element section. > Wind Load = P (As) > P = Wind Pressure (Lbs/Sq Ft) = .004(V^2) > V = Wind Speed > As = Effective Area of section =(Length)(Diameter)(2/3) > 2/3 is the shape factor for cylindrical tubing. Somewhere on the YS web site, there is a justification, such as it is, for using this obsolete formula. Applying it to the example I gave would give an effective area of 2/3 sq ft and a wind pressure of 25.6 lbs/sq ft for a wind load of 17 lbs. Notice that the wind pressure coefficient is .004, not .00256 like you see elsewhere. One thing has become a least a little clear: you only use the 2/3 with the .004 wind pressure coefficient and you do NOT use the 2/3 with the .00256 wind pressure coefficient. What you don't want to do is use the 2/3 with .00256 and get an optimistic number. Rick Karlquist N6RK richard@karlquist.com www.n6rk.com www.karlquist.com > -----Original Message----- > From: Pete Smith [mailto:n4zr@contesting.com] > Sent: Wednesday, February 27, 2002 9:43 AM > To: Richard Karlquist > Subject: Re: [Towertalk] Wind pressure calculations (2/3 factor) > > > Go to the Yagistress web site. K7NV has an excellent > tutorial there on > area calculations, and you can also get a demo of the > Yagistress software > that may be all you need. > > http://yagistress.freeyellow.com/ > > 73, Pete N4ZR > > Check out the World HF > Contest Station Database at > www.pvrc.org > > > > ```
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