In a message dated 99-04-30 10:34:42 EDT, you write:
> > What tower flex? You mean torsionally? That'll happen no matter what
> guy material you use.
>
> But is not Phillystran more flexible at the same tension than EHS? Thus
> would
> it not allow a little more sway under high wind gust conditions?
>
Flexible? That's not a term used in tower/guy specs. The momentary
'stretch' (if any - I'm not an engineer either) of these materials is of no
practical consequence. I'm assuming of course that you follow the
manufacturer's specs in all cases.
> > Vibration? Haven't run across that one before.
>
> Are not the strands of EHS more stiff (and-to-end) than Phillystran, thus
> vibrations
> initiated at any point would be transmitted to anything connected? Or do
> the insulators effectively deaden that?
Even *if* measureable, it's of no practical consequence.
>
> > Joint stress? Leg compression is the biggest factor in tower
forces.
> > The leg joints are stronger than the rest of the leg.
>
> I was imaging the tower swaying a bit in 125-150mph gusts and rocking
around
> the connecting bolts. (Sounds like something from a song, "rocking around
> the tower bolts, have a happy hurricane ..." :-) )
>
The whole tower structure is designed for different windload/windspeed
scenarios and they DON'T rock.
> > While I don't have the technical data in front of me, if you're
> asking
> > about possible elongation of EHS and Phillystran - for our ham purposes
> they
> > are both small enough that you don't have to worry about it.
>
> Not permanent elongation but momentary under high stress moments?
Even *if* measureable, it's of no practical consequence.
>
> > Here's a suggestion - use the EHS-with-insulators on the bottom set
> and
> > 50% Phillystran/EHS on the top set. I think this'll reduce your risk
> exposure
> > while giving you some Phillystran benefits.
>
> 50%? I would use a 4 guy top rather than three? Will have to explore
that.
>
What's a "4 guy top"? 50% refers to the top half of the guy being
Phillystran and the bottom half being EHS w/insulators.
Most of these questions that you are asking are things that you are
perceiving that don't have any practical considerations. You're over-thinking
the whole structure. Follow the manufacturer's instructions. If you're
worried about Phillystran being more likely to be cut by things flying
through the air - then use EHS w/insulators. And get an engineer involved.
Everything else is background noise.
Cheers, Steve K7LXC
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