[TowerTalk] Dacron or Philyistran

[john at kk9a.com]

I use Phillystran with stainless steel cable clamps on all of my boom
trusses.  Big Grips just seem too big for an antenna boom.  It some cases
Grips may defeat the purpose of using non-conductive cable.

John KK9A


To:	Jim Thomson <jim.thom at telus.net>, towertalk at contesting.com
Subject:	Re: [TowerTalk] Dacron or Philyistran
From:	Grant Saviers <grants2 at pacbell.net>
Date:	Thu, 22 Dec 2016 13:25:36 -0800

I'm using Philly and use the grips for the boom guys. On my 10m 5L I think
the Philly guy grip on the boom truss does detune the antenna a bit.
Suspicions about difference of model vs real swr. Not sure. IMO, grips on
element trusses are best avoided.

The tests of three cable clips I did on large 25k# Philly proved they really
don't work. Clips on smaller Philly are probably ok. Three clips are common
for some commercial antenna boom trusses using 1200# Philly. I think they
need tightened until the plastic is completely deformed as the sheath cold
flow/creep loosens them over time. Basically the clip has to bear on the
Kevlar. Maybe three tightenings to 80% of wire rope torques over several
warm days to get there. I found a loose set of 3 clips on a 4L steppir boom
guy that were torqued once at installation. And certainly not with a torque
wrench. My 80m 86' dipole element 1200# Philly double guy uses 4 clips and
the 40m 2L 28' boom the same. No visible sag after 4 years.

I also disassembled several very well constructed large yagis that used
Nicopress sleeves on the 2100# Philly boom truss (48' x 3"). I hadn't seen
that before and they all showed full squeeze out of the sheath and no
slippage after 8 years in service. I saved a couple and some day will do a
tension test of Nicopress vs a grip and clips on the 1200 and 2100# test
Philly.

Philly has less stretch and longer life than dacron and would be the way to
go IMO. For 40 and 80 the Philly grips on a boom are probably short enough
to be RF invisible.

Destructive testing with ice loading is not a good way to find out that the
clips slip. Or that saving a few bucks by using bent eyebolts rather than
forged ones wasn't a good decision.

Grant KZ1W