[TowerTalk] Phillystran

[Patrick Greenlee]

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 at 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 at aol.com
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk