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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