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[TowerTalk] how vertical is vertical

To: <>
Subject: [TowerTalk] how vertical is vertical
From: (
Date: Tue Mar 4 21:43:19 2003
In a message dated 3/4/2003 5:25:06 PM US Mountain Standard Time, writes:

> I'd be interested to know the basis of the "verticality" requirement... 1 
> part in 100 (about 1/2 degree) wouldn't appreciably change the loads at the 
> base (1% using the "small angle approximation"), and hopefully the design 
> isn't cutting it that close. (Assuming the guys are a reasonable distance 
> away from the tower.. all bets are off if the guy anchor is 10 feet from 
> the base of the tower...)
> There's a "do the job right" aspect, of course, and the advice to set it up 
> now for inevitable adjustment later is certainly sound.
> For a contractual document (i.e. you're hiring someone to put up a tower) 
> you need to provide "testable requirement".  If standard industry practice 
> is that it's easy to get it vertical to 1 part in 400, then there's no 
> problem imposing that as a requirement.
> However, if you're doing the work yourself, you're not necessarily 
> concerned about whether it meets some arbitrary standard, but more, whether 
> it's safe, and the "safe" requirement might be substantially looser than 
> the "pretty and good commercial practice" requirement.
> Jim, W6RMK

Hi Jim;

My EIA-222-D (yes, its old but its the most current I have here and this 
section probably hasnt changed) says;


Section 6.1 Standard

Section - Plumb - For guyed structures, the maximum deviation from 
the true vertical shall be one part in 400. For self-supporting structures, 
the maximum deviation from true vertical shall be one part in 250. 

Just like KI7WX already mentioned. 

The150' tower in question had a plumb bob (with possible wind deflection) 
indication of 12" off vertical. (One part in 400 allowable tolerance equates 
to 3" per 100' of tower. A 12" error in 150 ft of tower equates to 8" 
deflection per 100' of tower or a one part in 150......unallowable by this 

73,Bob K8IA
Mesa, Arizona USA
near the Superstition Mtns
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