Dick Weber, K5IU, did analysis of this problem in Determination of Yagi
Wind Loads Using the "Cross Flow Principle" in Comm. Quarterly, Spring
1993 issue. I believe this is the most comprehensive work on the subject
to date. 73, Dan, N5AR
> In thinking about Eric's question of windload on a helix,
> I came to realize I'd never seen a thorough approach to
> windload on a yagi.
> * Does anyone have a reference to a published analysis?
> * Thinking about it:
> * To what degree are 'hidden' elements shadowed by
> those before them? It probably depends on windspeed
> and element diameter, as well as spacing.
> * My guess is, "not at all", in which case, one sums
> the exposed area of the elements and degrades that by
> whatever the flat/round factor is. (.70?)
> * Further, I suspect that maximum exposed area occurs
> around 45 degrees, where one takes .707 of the exposed
> boom area, plus .707 of the exposed elements area,
> each multiplied by the flat/round factor, and then summed.
> I suspect a search in the IEEE journal might yield something;
> that's my next step.
> Has anyone seen reference to wind tunnel studies, in support
> of mathematical models/approximations?
> Jim Jarvis/N2EA
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