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

 To: [Towertalk] Wind pressure calculations (2/3 factor) k4oj@tampabay.rr.com (Jim White, K4OJ) Wed, 27 Feb 2002 11:41:20 -0800
 ```sounds like a job for Yagistress Man k4oj ----- Original Message ----- From: "Richard Karlquist" To: Sent: Wednesday, February 27, 2002 8:32 AM Subject: [Towertalk] Wind pressure calculations (2/3 factor) > I am trying to do a simple wind > pressure calculation on an antenna, > but I am confused about how to do > it. I see conflicting information > on towertalk archives and various > ham vendor sites. Let me see if > I can get a consensus on a very > basic example. > > If I have a 1 inch diameter round > tube 12 feet long in an 80 MPH wind, > what is the wind pressure. > > The projected area is 1 square foot > (ie the shadow the tubing would cast > on a plane surface) > > The total frontal area is pi/2 times this > or 1.59 square feet > > Some references say to multiply by 2/3 > to get "effective area" whatever that > means. Other references talk about 1.5, > which is the reciprocal of 2/3 and close > to pi/2. > > Anyway, some sort of area needs to be > multiplied by some fudge factor and then needs to > be multiplied by wind stagnation pressure. > Am I correct in assuming this is 30 lbs > per square foot for 80 MPH? I am thinking > this is an ideal value in free space > (ie pushed by an airplane traveling at > 80 MPH). > > I see references to a "UBC basic wind speed > of 80 MPH" where 80 MPH doesn't mean 80 MPH, > rather it refers to a table of pressure vs > height. I see at 70 feet this is something > like 24 lbs/square foot. This seems to imply > a ground effect. > > I'm not trying to apply for a building permit, > I'm just trying to see if an antenna will > survive 80 MPH winds. > > Can anyone boil this down to something > simple? > > Rick Karlquist N6RK > richard@karlquist.com > www.n6rk.com > www.karlquist.com > _______________________________________________ > Towertalk mailing list > Towertalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk > ```
 Current Thread [Towertalk] Wind pressure calculations (2/3 factor), Richard Karlquist [Towertalk] Wind pressure calculations (2/3 factor), Mike [Towertalk] Wind pressure calculations (2/3 factor), Red [Towertalk] Wind pressure calculations (2/3 factor), Jim White, K4OJ <= [Towertalk] Wind pressure calculations (2/3 factor), Michael Keane, K1MK [Towertalk] Wind pressure calculations (2/3 factor), Richard Karlquist [Towertalk] Wind pressure calculations (2/3 factor), Michael Keane, K1MK