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Re: [TowerTalk] Dacron or Philyistran

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



On 12/22/2016 12:38 PM, Jim Thomson wrote:
What works for guying a boom ?    What works best for guying a 51-57 ft long 
shortened 40m ele
or a 68 ft long 80m ele ?

Im inclined to use SS cable for any boon truss.   But dunno about  dacron vs 
phily  for an ele truss.

Jim   VE7RF
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