Date: Thu, 25 Aug 2011 20:05:56 -0400 (EDT)
Subject: Re: [TowerTalk] antenna location for hurricane
In a message dated 8/25/2011 2:49:07 P.M. Pacific Daylight Time,
> I hope for the best, but I don't believe that this antenna will survive
95 mph wind gusts...
Regardless of the potential or real wind effects, I would suggest making
sure your homeowner's/renter's insurance is paid up. Everything else is
mostly out of your control.
Cheers & GL,
## impact PRESSURE goes up to the SQUARE of the wind velocity ! A 100 mph
is 400% more than a 50 mph gust. At 111.8 mph, it's 500% more ! Forget
average wind speed for a moment. It's the gusts that will bust things apart.
You only need
a gust to last a few seconds to do severe damage, and most gusts last from
## Hope you folks have invested in a good quality, heat treated 4130
chromolly mast, [104-120 ksi yield strength]
or a 1026/1027 DOM mast [75-90 ksi yield strength]. Trying to remove a
bent mast, after the fact, is extremely
dangerous at the best of times, esp if a crane can't be brought to the site.
## Most of these commercially made yagi's I see have poor mast torque
compensation. And when you see the typ torque
numbers, like F-12 ants..... they are for a 70 mph wind. In a 100 mph wind,
those same mast torque numbers will
DOUBLE. Reducing mast torque to almost zero is easy to do. Either a torque
comp plate is used at the short end of the boom,
typ the REF end of the boom.
Or equal portions of boom are on either side of the mast, and the light end
has a counterweight stuffed into it, and secured.
## 100 mph gusts are not something to trifle with. Glass will break @ 100
mph. I'd suggest taping window's, secure everything in site.
High winds like that will make mincemeat of tree's. A buddy lost his tower
last spring, cuz a tree [ with a poor root system] came down
on his 3/8" polygon guy wires, slicing the top 2 x guys wires, then the bolt
in the rohn equalizer plate sheared off. The top 30' of the tree had
sliced through the bottom 30' of the guy wires, just before the polygon guys
morphed into the EHS steel cables. Distance from base of tree to
base of tower was >210'. A paltry 52 mph gust brought down the tree.
TowerTalk mailing list