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Re: [TowerTalk] Phillystran damaged?

Subject: Re: [TowerTalk] Phillystran damaged?
From: "Roger (K8RI)" <>
Date: Fri, 30 Oct 2009 01:01:24 -0400
List-post: <">>

Mike wrote:
> My 4L SteppIR uses small diameter Phillystran as a bridle for the boom, 
> clamped with saddle clamps. I have the antenna on the ground, and was 
> going to replace the saddle clamps with stainless steel ones.
> When I took off the old clamps, the 'stran is crushed absolutely flat 
> where the U-bolt side bore on it. It appears as tho there is nothing in 
> the jacket. The jacket isn't broken, only flat.
> Is the Philly cut or broken, or is that much crush normal? It doesn't 
> seem like a good idea to breach the jacket to have a look-see.

The core of Phillystran is Kevlar (IIRC) and is made up of many fine 
strands. When clamped that allows the jacket to flatten or distort 
considerably without a great deal of loss in strength.  OTOH any time 
you flatten a cable it loses some strength that varies widely between 
materials.  The black jacket is purely weather proofing as Kevlar is 
affected by water and Ultraviolet light.

Using saddle clamps doesn't sound like a good way to attach the boom 
truss if the cable is just placed under either the U-bolt or saddle. I'm 
assuming you are using the small (1200# test) cable.  That is normally 
terminated by using a thimble and three cable clamps. Use sufficient 
tension on the cable clamps, but not enough to damage the Phillystran. 
Don't crank the nuts down tight like you would on steel cable.  Proper 
tension on the clamps will still noticeably distorte the cable. That's 
why they use 3 with less tension instead of 1 or 2 that are tightened 
down more.  Remember the U-bolt" clamps on the "dead side" while the 
saddle clamps on the side with tension.


Roger (K8RI)
> 73, Mike NF4L
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