[TowerTalk] Phillystran damaged?

[Dick Green WC1M]

K8RI wrote:

> 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.  

Generally good advice, and of course you don't want to damage the
Phillystran, but in the case of the 4-el SteppIR boom support, I would
advise cranking the nuts as tight as you can by hand. The reason I say this
is that I didn't do so on one of the 4-el SteppIRs in my 3-stack, and the
boom support pulled out of the clamp. So the antenna was without support on
half the boom. Unfortunately, the end that slipped out was the one attached
to the boom and was consequently out of reach from the tower. It was the top
antenna, so I wasn't crazy about the idea of tramming it down to fix the
boom truss. 

I contacted K7IR at SteppIR about it, and he told me that the boom is way
overdesigned and the truss is there mostly for cosmetic reasons. So I left
it that way for months, until I had another reason to take that antenna down
(the second director motor had, unbeknownst to me, been damaged by that end
of the antenna being dropped hard on the ground during installation.)

Later, I spoke with K1DG, who had exactly the same experience with the boom
truss on one of his 4-el SteppIRs. He devised an ingenious repair method
whereby he used a snap hook attached to a fishing pole to snag the eyelet on
the boom end of the truss. So, if it lets go you can repair it, but not
without some difficulty.

Of course, if you're one of the many SteppIR owners with a tilt-over crankup
tower, my advice may not apply.

73, Dick WC1M

> -----Original Message-----
> From: Roger (K8RI) [mailto:K8RI-on-TowerTalk at tm.net]
> Sent: Friday, October 30, 2009 1:01 AM
> To: nf4l at nf4l.com
> Cc: towertalk reflector
> Subject: Re: [TowerTalk] Phillystran damaged?
> 
> 
> 
> 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.
> 
> 73
> 
> Roger (K8RI)
> > 73, Mike NF4L
> >
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