Is 20 lb/sq ft correct for 90 mi/hr winds? I've run several of the published formulas in the past and seen other references that would indicated that 36 lb/sq ft is a good number to use at 90 mph. I
Clay, Yes, you're in the ballpark. The formula for drag is 1/2* rho*velocity-squared*frontal-area*coefficient-of-drag. I calculate about 26 lbs force for 90 mph for 1 sq-ft frontal projection area. T
36 lb/sf is more like 120 mi/hr... lb/sqft = Vmph^2/391 is the equation. 8100/391 -> 8000/400 -> 20 approx 391 is the half the density of air in weird units (F = 1/2 * A * rho * V^2) ________________
Indeed.. I just used 1.0 for Cd for rough and ready order of magnitude. I was thinking in terms of a tubular free standing tower (as opposed to, say, a lattice HDBX style) 1.3 might be a reasonable n
Jim, Yes, I figured you used a Cd of 1.0, which is a reasonable starting place. Nice to know there is another "aero" guy on the towertalk list. Below is a link to some very good information on commun
Is 20 lb/sq ft correct for 90 mi/hr winds? I've run several of the published formulas in the past and seen other references that would indicated that 36 lb/sq ft is a good number to use at 90 mph. I
Thanks for the info. I don't know as much about this as I'd like, but I'm learning. From your comments I assume that 20-26 lbs would apply to round tower legs (Rohn 65G here) and typical yagi booms a
Clay, Great question! Difficult answer. I'm assuming that the projected areas are the same for both the 1/2" and 2" tubing in your question. It may be counter-intuitive, but many times the smaller di