I am curious about how antenna manufacturers and antenna mechanical
design programs determine the maximum windload ratings for an antenna,
in particular yagis.
It occurs to me that for a typical yagi that is designed for say a
maximum windload of 100 MPH, stress is calculated on the exposed surface
area of the elements against a maximum allowed calculated stress,
assuming that the wind in worst case conditions is at right angles to
the largest exposed area - ie) at rights angles to the wind.
However, it is obvious from seeing pictures of yagis in very high winds
that the antenna is not totally at right angles to the wind in high wind
conditions. ie) The elements bend (substantially) and thus the exposed
area is reduced.
Is the bending taken into account in designs and published ratings, or
is this always just an inherent additional safety factor?
--
Gerald Boutin, VE1DT
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