Pete Smith wrote:
> This assumes that elongation of the Phillystran for a given load is the
> same as EHS. In fact, according to K7NV
> <http://wiki.contesting.com/index.php/Guy_cable_data> 6700-lb Philly
> elongates about twice as much as 3/16" EHS and almost 4 times as much as
> 1/4" EHS which is rated for the same breaking strength.
>
But the elongation/stretch of either is pretty much meaningless except
for precision positioning and even then takes place with the initial
tensioning. It's doubtful there is much elongation associated with wind
load unless the tower is overloaded and/or the winds are very strong as
in approaching the system limits. In practice there is probably (I've
never measured it but I have seen the movement) more give in the
catenary with EHS than there is with the catenary AND elongation of
Phillystran. EHS has almost no elongation. What's 4 times almost
nothing? OTOH the *give* in both is slight unless someone runs into your
guy system with a tractor while you are up there. I know it's
substantial with EHS at 90 feet.(been there, done that, didn't like it
at all) I'll leave it up to some one else to test the Phillystran via
that method <:-))
Both are good, both have little give, and both are acceptable methods of
guying and even in 30 MPH winds you will not feel the tower move. Been
there and done that too. It was a much more pleasurable (or at least far
less stressful) than having the tractor test run on the guy system.<:-))
73
Roger (K8RI)
> I have 6700-lb Philly on my top guy set, with steel below, tensioned at
> 400 lb and the tower feels very steady. YMMV.
>
> 73, Pete N4ZR
> New Articles Daily - the Contesting Compendium at http://wiki.contesting.com
> The World Contest Station Database, updated daily at www.conteststations.com
> The Reverse Beacon Network at http://reversebeacon.net
>
>
>
> Roger (K8RI) wrote:
>
>> ...
>> Yes it's true you do not have a weight of EHS or the massive catenary.
>> There is so little catenary in the 4000 and 6000# test Phillystran you
>> really have to look to see it when sighting down the cable. However that
>> means the guys are less likely to be able to cushion shock.
>>
>>
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