Don, most all knots are weaker than the line in which they are tied,
i.e. the line will break at the knot before the undisturbed line will
break. . That said, I like your suggestion as boom trusses are not
long enough for economics to be an overriding concern that would
prevent oversizing the Philly to allow for derating due to the knots.
I would be very curious to know the reduction in breaking strength of
a termination consisting of a piece of Philly run through a hole just a
bit larger than the nominal diameter of the Philly in a metallic
substrate with a figure of eight knot (AKA stopper knot) tied in the
Philly. Perhaps someone with more knowledge of marlinspike seamanship
could suggest a suitable knot which has a lesser strength reduction.
Perhaps someone more familiar with Philly construction could comment on
the differences between the stress/force distribution in Philly as
opposed to popular rope construction such as double braid, twisted
three strand, etc.
Patrick NJ5G
On 10/23/2015 12:51 PM, Big Don wrote:
For completeness in the Phillystran discussion, the "Lok-Cube" should
perhaps be mentioned.
These were provided with 1990-vintage KT34XA antennas to terminate the 1/8"
Philly boom truss..
This item is basically a one-inch-or-so on-a-side plastic cube with five
thru-holes in the axial direction,
one in the center and one in each corner, hole diameter slightly larger
than the Philly.
A diagram in the instructions showed how to weave the Philly thru the
holes.
The Lok-Cube uses no positive clamping, all that keeps it from slipping
apart is friction of the Philly against itself, and the Lok-Cube, when the
termination is pulled tight. It is little more than a knot. Our XA has
been up, untouched for 25 years, including a couple of near-terminal
ice-storms, and the boom appears to be fine.....
Just a thought here - our gut feel is you could attach Philly just by tying
a knot similar to attaching a fishhook to a nylon leader. Maybe Grant could
try some in his 20,000# tension tester and see if it slips or pops at any
significantly reduced strength...?? Might start with the good-old Clinch
Knot
http://www.wideopenspaces.com/five-fishing-knots-you-will-ever-need-to-know/
Don N7EF
On Fri, Oct 23, 2015 at 9:31 AM, GMuller885--- via TowerTalk <
towertalk@contesting.com> wrote:
Folks:
I wish to thank all who have responded. I have gone to Phillkystran
web site and talked with their engineers and have come to the conclusion
that , YES I did use over kill on the size. However their conclusion was
that
there was no harm and no foul and the three clamps used at each terminus
would work very well. They did recommend that the saddle clamps should be
alternated starting with the saddle starting on the long side. As
mentioned,
" do not saddle a dead horse".
Again thank all of you that responded.
Gerald Muller K9GEM
GMuller885@aol.com
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