[TowerTalk] Dacron or Philyistran

[Grant Saviers]

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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