In a message dated 99-04-29 22:02:03 EDT, davidc@bit-net.com writes:
> I have access to both EHS and Phillystran and am
> debating between the two. The Phillystran is less of
> a pain to work with and I don't have to fuss about all
> that EHS metal messing up patterns ... but I worry about
> flying objects in the high winds of heavy summer lightning
> storms and from passing hurricanes shearing or damaging
> the Phillystran.
Hmm - good point. If that is your criteria, then EHS-with-insulators is
probably the way to go. Although a rip-roaring storm coming through might
blow it down anyway so it might not make too much difference.
Phillystran under tension can be cut quite easily with a semi-sharp
object so there is something in what you say.
>
> I am also wondering which is better for the longevity
> of the tower. Whereas the Phillystran allows the tower
> to flex more does that stress the joints more or do the
> vibrations due to EHS rigidity cause equal stress?
>
Phillystran has been around since 1973 so it'll last at least 26 years.
What tower flex? You mean torsionally? That'll happen no matter what guy
material you use.
Vibration? Haven't run across that one before.
Joint stress? Leg compression is the biggest factor in tower forces.
The leg joints are stronger than the rest of the leg.
EHS rigidity? A guy wire tensioned to 670 pounds doesn't care what the
material is - it's still tensioned at 670 pounds (10% of 1/4" EHS or
HPTG6700).
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.
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.
Cheers, Steve K7LXC
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