Roger (K8RI) wrote:
> Hmmm This was supposed to go to the group, but apparently I hit the
> wrong key...again.
>
>
> K7LXC@aol.com wrote:
>>
>> In a message dated 11/3/2008 12:45:53 P.M. Pacific Standard Time,
>> towertalk-request@contesting.com writes:
>>
>>
>>> This subject has been debated before. Your analysis of
>>> self-supporting
>>>
>> towers and guying is another example of misinformation! Let me suggest
>> you obtain the facts next time you post or other wise state that it is
>> your opinion. The company that manufactures the self-supporting towers
>> I use, RECOMMENDS guying ... fact!
>>
>>
> Angles are the angle between the tower and guy line.
> You can get the same answers by using the Sin of the angle between the
> guy and ground.
> Top guys on 100' 45G 3 @ 660# tension. Cos(30)*660 = 571*3 = 1715 rounded
> Middle guys 3 @ 440# Tension Cos(45)*440=311*3= 933
> Bottom guys 3 @ 440# Tension Cos(60)*440=229*3=660
>
> Tower sections 70# X 10 = 700.
> Base section 35#
> Antennas and mast 300#
> Rotator 45#
> Coax and control cables 100#
> Guy bracket assembly 23# X 3 = 69#
> Total = 1249 Give or take a 100.
> Were I to use EHS guys instead of Phillystran I could easily add another
> 300 to 600# while the Phillystran weights well less than 100# per 1000
> feet.
>
> That means they guys on my tower exert an additional 3300# on the base.
> That is well more than double the total tower and antenna system
> weight. Free standing, or Self Supporting towers are build
> considerably stronger than guyed towers as they have to serve the
> function of those guy wires internally. Some are designed to allow
> guying as well. The question them becomes, If permitted how does guying
> the self supporting tower affect the wind load and weight support
> ratings. Guying a tower with properly tensioned guys can easily add
> more than twice the load to the base. So a 1500# tower could end up
> with 4500# on the base structure.
Now figure the leg compression (unguyed) during a strong wind. You will
find that it's MUCH greater, and concentrates on the downwind leg(s),
and the conclusion is that reasonable guying will invariably increase
the wind load rating of any reasonable tower. It's not surprising that
most manufacturers do not recommend it though - it negates the advantage
of the self support structure...duh.
Steve K8LX
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