Bill,
I don't question that the numbers you got from the 1976 Rohn catalog
are not faithfull reproductions, perhaps I just don't
understand their interpretation.
>From the looks of it, 2.93 sq ft. may be the equivalent "frontal
projection area" of one section of Rohn 45G, which appears to
calculate out correctly, given the 1 1/4" OD tubing used in that
model.
Unfortunately, though somewhat loosly related, frontal projection
area and resultant aerodynamic drag can be 2 very different things,
depending on drag coefficients, Reynolds numbers, etc.
Just wanted to caution whoever requested these figures, that if the
application is unconventional, and critical to property or safety,
a consultation with an engineer might be in order. These things
do NOT scale linearly, so even if the drag force components are given
at a single windspeed, that ratio may not stay the same at a different
speeds.
Chris-AI4MI
I have a catalog from 1976, which gives wind load per lineal foot for
25G
and 45G.
25G has 7.62 pounds of load per lineal foot at 30 pounds/sq ft. This
gives
.254 sq ft/lineal foot. The whole section is then 2.54 sq ft.
45G has 8.78 pounds for the above conditions, which equates to .293 sq
ft/lineal foot, or 2.93 sq ft for the whole section.
The catalog does not have 55G or 65G in it, but you can probably
extrapolate
by comparing member sizes in the Rohn catalog.
Bill, N5TU
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