[TowerTalk] Phillystran Tension Gage

[JVarney]

I'm not quite understanding the "probably"?  If you calibrate
a simple side force deflection meter with the actual rope,
then it will fully take into account any anisotropic or
nonlinear behavior.

OP's target tension is 150 lbs. Take a 2x4, screw on two small nylon
sheaves about 3 feet apart. Hang some pre-stretched Philly from a
strong tree limb, put 150 lbs of weight on the cable. Use a fish
or luggage scale halfway between the sheaves and pull like a bow
and arrow.  Measure X inches of sideways deflection with Y lbs of
pull.

On the tower, tighten guys until the same X and Y values are
achieved.  Done.

73 Jim K6OK



Grant Saviers wrote:

Calibrating against the actual fiber is *probably* good enough
for ham tower work, BUT

Be aware that the Kevlar fibers of Phillystran behave very differently
than steel wire. The Kevlar fiber is very strong axially with about
60% the modulus of steel. The fiber also has very complex lower
modulus behavior longitudinally, the fibers are anisotropic.