[TowerTalk] Dacron rope

Jim Thomson jim.thom at telus.net
Wed Apr 12 02:07:43 EDT 2017

Date: Tue, 11 Apr 2017 17:29:22 -0400
From: "john at kk9a.com" <john at kk9a.com>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Dacron rope

The water is conductive, probably the rope is not that conductive. I
always use Phillystran on elements and insulators at the end of dipoles
where it connects to rope. My 40m OptiBeam uses rope for an element truss
but it has a plastic insulator where it attaches to the element. If your
rope was attached near the tip of the element and you were running a KW it
would likely be destroyed.

John KK9A

## Most 40 + 80 els that are trussed, will only be attached part way out the ele.
But still, if the dacron is soaking wet, it could conduct just enough so the ele now 
thinks it has a high resistance leg, hanging off to one side...sorta like adding  one half 
of a high resistance T bar capacity hat, which will of course electrically lengthen
the ele, and de tune it to a lower freq.   So if an insulator is installed, it should
be at the dacron to ele interface..and not at the other end of the dacron, at the
ele to boom riser. 

##  The dacron is a lot stronger than the  typ insulators.  On those plastic
insulators, the ones that are aprx 5-7 inches long, with the serrations  to increase
V stand off, they typ come with steel inserts in each hole.  I have had to drill those out
on most of them, so I could use stuff like 8ga  RW-90.  I could see also having to
drill them out  for darcon rope, depending on size used.    They are typ just 500 lb
rated, which is way less than  .1875  or  .3125 dacron. 

##  perhaps solid fiberglass  rod, like what is sold by max gain systems, might be the
ticket.   They have it up to 1.5 inch solid.  Then u could make your own insulators, any
length, and any hole size on each end.  You could also cut some serrations into it, if you wanted
increased V stand off.  I have  tried using a single uhmw disc, aprx 2 inch OD, with a 1 inch ID hole,
which slid over a solid 1 inch fiberglass  insulator, then rtv into place.  That alone will increase V
stand off through the roof.  Problem was, the uhmw I used was white, and .125 thick.... turned
brittle after 2 years in the sun...junk.  Grey PVC or abs would do the trick. 

##  dunno what the tensile... aka stretch  strength is with the mgs solid fiberglass  rods ?   I think as
long as the rod was big enough diam..and holes away from the extreme ends, it will  suffice.   Last thing
anybody wants is a busted insulator on a 40m yagi...after a heavy wet snow  or ice load. 

Jim   VE7RF

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