[UK-CONTEST] Versatower guy rope sizes

[G3RAU at aol.com]

The Versatower recommended guying layout for a 60ft mast specified a  40ft 
radius, 
and the plastic covered galvanised steel guy ropes were 5mm 7/19  at  the 
top and
 5mm 6/19 lower down.  The D shackles and bottle screws were all  500KG 
rating. 
 If non metallic ropes were specified Versatower supplied 10mm pre  
stretched 
black polyester.
 
In your case Alan I would most certainly not use a rope with a potential  
100mm 
stretch, the mast could get into a heavy rocking mode and destroy  a big 
boom 
antenna due to the rocking motion which stretchy guys only serve  to 
exacerbate.
 As you say, using a stronger rope means proportionally less stretch  and 
hence
 less rocking, so that is the way to go.  Guyed Versatowers  were supposed 
to
 be able to move "an inch or two" at the top in order to prevent over  
zealous guy 
tightening producing excess stress on the internal lifting cables. How  much
 rocking you can tolerate depends on the antenna you are using,  personally
 I would get two people heaving  on opposite top guys  and keep tightening 
them until no serious boom rocking  of the antenna can be detected. 
 
One solution is perhaps to make the top part of the guy synthetic  where it 
will 
not upset the antenna radiation pattern, and make the lower part steel  
which 
stretches much less and is far more immune to damage.   This method reduces 
the overall stretch even more and may well  prove economical, (but  choose 
a 
non resonant length for the steel).
 
 
There is a lot of good design information about ropes & guying to be  found 
at 
_www.mastrant.com_ (http://www.mastrant.com/)  where you will  find a 
number of calculators to evaluate stress 
and loadings on masts and guys, and some general advice.

 
73 Derek G3RAU