[TowerTalk] Antenna surface area

[Tod - Minnesota]

Hank is bringing us back to reality here with these six practical
statements--

(1). For a flat plate of W width and L length with the W dimension normal to
the wind the projected area is the width W times the length L. It is really
that simple.

(2). A cylindrical member of diameter D and Length L has a projected area of
L X D.

(3). At the normal range  of element sizes and distances between elements it
is safe to assume that the elements do not shade each other and that the
total projected area is the sum of the elements and any connnection items
that have an normal area in the same direction.

(4). The same is true for wind normal to the boom which might have a shape
factor coefficient because it is of large enough diameter. (The UBC uses 1.0
for elements less than or equal to 2" in diameter and 0.8 for cylindrical
elements large than 2" in diameter.)

(5). In reality considering a triangular open trussed type tower system,
unless it is extremely short, the wind load on the tower is the largest
force in the system, not the wind load on the antenna.

(6). The absolute antenna load is most important for the selection of the
mast materials and size and of course the load capacity of the rotor.


Tod, KØTO


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