[TowerTalk] Wind Ratings (and tower location)

[Shawn Donley]

Just some observations and thoughts...  nothing too serious here.


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.


But... I've always wondered what drives this requirement at all (forget the 75% part and how towers fail).  Is it safety (for your neighbors) or aesthetics (perhaps further from the property line means less visible in most cases)?


If it's safety, why don't said ordinances prohibit planting a tree without a similar setback?   A red oak 18" in diameter and 72 ft tall weighs about 5200 lbs (source:  https://www.ncrs.fs.fed.us/pubs/ch/ch01/Chvolume01page401.pdf).   A UST HDX-572MDPL weighs in at 1600 lbs (transport weight).   Which is likely to do more damage?


Possible answers:


1.  There are lots of trees and not many towers.

2. It is generally recognized that trees fall and can cause damage and even death.  Society has accepted this risk.  Not so for man made structures like towers.

3. It will probably take 35 years for the tree to reach 70 ft and longer yet before it falls.  The folks who planted it will be long gone (no one around to sue).


But at the end of the day, you're far more likely to experience damage or injury from a tree than a tower.


So the next time you're down at your friendly inspections and permits department, casually ask the question about siting towers and planting trees.   In the months that follow, if you read about  a new tree ordinance, you really do live in a nanny state and it's high time to move to a new QTH (if you can find one).


N3AE





https://www.ncrs.fs.fed.us/pubs/ch/ch01/Chvolume01page401.pdf


gg