[TowerTalk] Guying a self-supporter

[Roger (K8RI)]

Steve Maki wrote:
> Roger (K8RI) wrote:
>   
>> Hmmm This was supposed to go to the group, but apparently I hit the 
>> wrong key...again.
>>
>>
>> K7LXC at aol.com wrote:
>>     
>>>  
>>> In a message dated 11/3/2008 12:45:53 P.M. Pacific Standard Time,  
>>> towertalk-request at 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.
>
>   
Of course the self supporting structure is far heavier and more 
expensive than the guyed structure. It also takes a lot more concrete in 
the base.  OTOH it takes up far less space, too.  Were I not retired and 
still working at my old job I'd have a pair of them up. Crank up AND 
self supporting.

Roger (K8RI)
> Steve K8LX
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