[TowerTalk] Wind Ratings

[jimlux]

On 6/12/17 9:15 AM, Wilson Lamb wrote:
> “Most zoning ordinances stipulate a setback requirement for a tower.  Around here, the setback from the nearest property line must be equal to or greater than 75% of the total height of the tower.”
>
> And what’s the sense of that?  Why isn’t the top 25% dangerous?  Actually, it’s likely the most dangerous.  It’s moving fastest and has that big ol’ antenna antenna on it.
>
you're asking for an engineering rationale for a "that sounds like a 
decent requirement" kind of rule.

I suspect that a lot of these get defined by "there's a lot of 40 foot 
things around, and lots are 60 feet wide, and if we make it 100%, a lot 
of people will yell, but if we make it 75%, then the number of people 
who complain is sufficiently small"

Or, based on somebody else's 75% rule, which is based on yet a 3rd 75% 
rule, etc.

Or it's based on guying radius, and nobody thought that it should change 
for a self supporter.

I've also heard of 50%, and of course, there's plenty of 100% rules out 
there.