[TowerTalk] Quick wind question

[Jim Lux]

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..)





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