[TowerTalk] Tower Questions

[Bill Coleman AA4LR]

On 4/5/00 3:56 PM, Kurt Andress at K7NV@contesting.com wrote:

>Start with asking the manufacturer for the answer. If that doesn't work,
>get the physical dimensions from them and do it yourself. It's
>easy...length x diameter, add them all up and do it for all the elements
>and then the boom. The greatest one is the worst case for that antenna.

I know enough about aerodynamics to know that the shape of the element 
has a lot to do with its drag qualities. Round elements are moderately 
draggy, but oval shapes would be less so. (the bluff front edge isn't the 
problem - all "aerodynamic" car designs to the contrary -- it's the 
untapered trailing edge that causes all the drag) And movement of the 
element can change its drag profile - an element that can vibrate back 
and forth in a flutter will have a lot less drag than one that stays 
rigidly still. 

So, you can't just compute wind drag by pretending the elements are 
perfectly flat blockers of wind. 

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@radio.org
Quote: "Boot, you transistorized tormentor! Boot!"
            -- Archibald Asparagus, VeggieTales


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