[TowerTalk] Guyed + self supporting /2 ??

[Steve Maki]

No you didn't read it correctly Roger. His opinion was exactly as 
stated, that a guy system could be designed for a (existing) self 
supporter that would favorably impact the load rating. Maybe only a 
little, maybe more depending on lot's of variables. And yes it was just 
"off the cuff".

My point was, which I though was obvious:

To say that you "must not guy a self supporter" implies that in every 
case, the tower will be weakened by the addition of a guy system. That 
is simply not true.

If that is not what was meant, then it was misstated. Consider this an 
academic exercise if you can.

That's all I'm going to say on this until I can call in a favor and get 
someone with a modeling program to run some reasonable *what if* case 
studies.

-Steve K8LX

On 10/16/2014 8:33 PM, Roger (K8RI) on TT wrote:

> On 10/16/2014 7:02 AM, Steve Maki wrote:
>
> I see this as a safety issue and doing things differently than the
> manufacturers design and limits is risky, even if they do design in a
> substantial CYA safety factor. Changes can cost your insurance.
>
> Sorry, I can not accept what one engineer says "off the cuff". If I read
> it correctly he did say the tower had to be designed that way and you
> talked about it being silly to design one that way. So, which is it?
> Just hooking guys to a tower (to add strength) could just as easily
> reduce the strength unless the installation were properly engineered.
> Even if as he says, you could add guys, would there be any net gain in
> strength unless the tower were designed that way to begin with?  If
> there was a net gain, would it be enough to be useful.  The steel angle
> used in most self supporters is not designed to withstand a pull on it's
> own.  We'd need a band around the tower at that point.
>
> The purpose of guys is to add strength and stability.  It's far better
> and safer to start with the proper tower system to support what you plan
> on, rather than beef any tower beyond its design limits.  There would be
> no other valid reason for adding guys. Reducing the base is just another
> way of  fiddling with the design limits.  I much prefer to use towers
> within their design limits.
>
> For any of us to just add guys to a self supporter is not smart and you
> both said as much, but we shouldn't make statements that are likely to
> encourage hams (without an engineering background) to go ahead and just
> add guys.  It puts them in the area of research and could likely void
> their insurance.
>
> In the past, I've experimented with towers and antennas, knowing full
> well if it faile my insurance would likely not cover it.
>
> Most ham, self supporters are crankups.  There are a few exceptions.
> http://www.rogerhalstead.com/ham_files/skyhook.htm  but that is one that
> took a lot of engineering and planning.  The guys in the engineering
> department donated a lot of time on that one.  There are 3 semi loads of
> steel in that tower (and a lot of money)
>
> 73
>
> Roger
>
>
>> On 10/16/2014 2:49 AM, Roger (K8RI) on TT wrote:
>>>
>>>> After much repeated discussion on this forum over the years I asked a
>>>> structural engineer about this, and he confirmed what you are saying -
>>>> that basically a guy system could be designed for pretty much any
>>>> *self supporter* to favorably affect it's load limits (within a
>>>> reasonable footprint), but that it would be silly to start out
>>>> designing one that way since it would be a waste of materials. If
>>>> you're going to guy a tower, use a *guyed tower*.
>>>>
>>>> But when someone says *you MUST not guy a self supporter*, it makes me
>>>> cringe.
>>>
>>> Why. A self supporter can be designed for guys, but most are not. If
>>> they are not designed with the guy forces taken into account, you are
>>> just gambling.
>>
>> Why? Because it's just not true to say that. Note that I'm not
>> recommending anything, other than to speak accurately..