[TowerTalk] AlumaTower T-50H guying questions

[jimlux]

Gene Fuller wrote:
> If possible you might try to check with the tower manufacturer and see how 
> marginal the vertical forces would become if you still used 25 and fifty but 
> just brought the anchors  inside you property line. You probably would find 
> that you could buy a lot of safety factor without much, if any, risk from 
> the vertical loading. Otherwise, just don't tighten the uppers too much and 
> you'ld have the protection in case you got caught in a blow with it up. If 
> there was ever enough wind to make it fail in compression, it probably would 
> have failed from bending moment much earlier if the uppers weren't there.
> 
> ----- Original Message ----- 
> From: "Mike Short" <mike.short at mchsi.com>
> To: <towertalk at contesting.com>
> Sent: Saturday, November 28, 2009 1:52 PM
> Subject: [TowerTalk] AlumaTower T-50H guying questions
> 
> 
>> Alumatower shows two guy wires at 25ft and 50ft when extended, and the guy
>> anchor is 40ft from the tower.
>>
>> I want to guy it at 25ft only because of room issues in my back yard. It
>> will be nested for the most part, and only extended while in use. I will 
>> be
>> putting a hexbeam and maybe a Cushcraft A505S 6M 5 element beam on it.
>>
>> If I guy it at 25ft only, would I want to guy it using the same angle as 
>> it
>> is at 50ft? Would that be the same downward pressure? If so, it would move
>> the guy anchor inward to 29ft.
>>
>> Would this be reasonable/safe?
>>

The operative word here is "safe"...you need to define what you mean by 
that, and once you've done that, what you can do and what's reasonable 
will probably become evident.

Bear in mind that "failure" of the tower system isn't an all or nothing 
proposition, too.  There's varying degrees of failure ranging from bent 
structural members to complete collapse.

Here's some possible meanings
1) Under the worst case wind conditions, the tower remains perfectly 
functional and intact.
2) Under the worst case wind conditions, the tower will get bent and 
need potentially significant repairs, but no hazard to life or property 
(other than the tower) exists.
3) Under the worst case wind conditions, the tower collapses, 
potentially damaging other things, but entirely within your property 
lines, so nobody else suffers.


Then, duplicate these statements replacing "worst case wind" with 
"normal wind"...


Once you've kind of got that figured out, then you can decide what's 
"reasonable".. If your tower is next to a preschool full of little kids, 
your risk acceptance strategy is probably different than if it's out in 
the back 40 of your 640 acre ranch.


For myself and a hobby application, I think I'd go for "can't fall down 
and hurt someone/something, but I don't care if it is permanently 
damaged and needs repair", which is very different from a "must remain 
functional no matter what" that a lot of the analytical tools assume.