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## Re: [TowerTalk] Quick wind question

 To: Jim Lux Re: [TowerTalk] Quick wind question Martin Sole Sun, 18 Mar 2007 20:47:49 +0700
 ```Jim, Thanks, nice and simple eh? :-) Reasonable = +/- 20% then a tad (metric or imperial tad, not important) Of course the answers now breed more questions. JUsta check list to see if I'm doing this right. rho= Air Density in kg/m^3 Cd= coefficient no units but I have determined that for a roughly rectangular shape 2 is 'reasonable' Area=m^2 wind=kph^2 Wind drag = ? (units) kg/m^2 ? Bending moment = force, units same as wind drag? Add drag for pipe calculated at say half length, ok. Yield strength for the pipe is quoted as 250 Mega Pascals, multiply by 145.04 to get in psi. Many Thanks Martin, HS0ZED Jim Lux wrote: > At 05:35 AM 3/18/2007, Martin Sole wrote: > >> Folks, >> >> Just talking with a friend about a 'wind problem' is there a nice >> formula that will give a reasonable estimate of the likely wind >> survivability based on: >> >> a mass A of surface area B suspended C distance up on a pipe of yield >> strength D. >> >> >> Thanks >> >> Martin, HS0ZED >> > > > Depends on what you call "reasonable" > > You can estimate it by taking > Wind drag = rho*Cd*Area*Vwind^2, where rho is density of air and Cd > is the drag coefficient of your thing > A cylinder (e.g. a pipe) has a Cd around 1 (sometimes lower, > sometimes higher, depending on size of pipe and speed of wind) > > The bending moment developed at distance C from the ground is roughly C * > Fdrag > You also need to add the drag of the pipe itself, which for > approximation can be considered as acting at a point halfway along the length > > There's a standard formula for the strength of a hollow tube of a > particular material (I don't remember it off the top of my head..) > > > > > > >> _______________________________________________ >> >> >> >> _______________________________________________ >> TowerTalk mailing list >> TowerTalk@contesting.com >> http://lists.contesting.com/mailman/listinfo/towertalk >> > > > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk > > > _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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