[TowerTalk] Antenna Rope report

[jimjarvis@comcast.net]

TT:

Back in May-June, we had a discussion about rope for antenna haliards.
At that time, I reported having acquired  1/8" dacron over kevlar line from
Radio Works, to use with my 'bugout' antenna.    We're in process of moving,
and it was time to strike the system & report on wear and handling.

This system had something like 18 weeks aloft.   an 80m 1/2 wave was installed in trees @ 75' using a bow and arrow.   The method is to simply lay the haliard over the tree,  then route it down the trunk and tie it off to a cleat.   Flexibility of smaller 
branches provides the only strain relief in the system.

Handling:   

Going up, the dacron/kevlar line is stiffer than pure dacron, and a little heavier.  While it's still possible to hoist it with gametracker string from my bow, it's harder to get it to slide over branches.   It appears to have more surface friction.
                 
Because of the stiffness, neatly coiled and stowed dacron/kevlar tends to take a set, and does not easily uncoil.   It tends to tangle.   

Wear:  

There was visible wear in places where the line went over stiff branches.  It was significant enough to produce concern.    By comparison, 1/8" dacron which had been up in Vermont for 3 years or more showed solar bleaching, but no visible surface wear.   (I had a 500' spool of the used dacron weave still available, for comparison.)

Recommendation:  

The dacron/kevlar hybrid is rated at 770 lbs tensile strength, versus 375 lbs for the #14 insulated wire itself.   The 1/8" dacron weave is rated at 550 lbs.   The latter is easier to handle, seems to wear better, and more closely matches the breaking strength of the wire itself.   Additionally, the dacron provides 5% stretch, making it more tolerant of peak loads.

I do not recommend the dacron/kevlar line for my type of tree installation.
I'm sure it's fine for handling antennas which are held aloft by towers, or tree-hoists with proper blocks, anti-chafe, and strain relief.    

In the new house, the 80m half wave will be installed as an inverted Vee, with ONE tree as the center hoist.   The wear situation will be markedly different.  

Funny aside:   One of the potential buyers expressed concern about the health of the mature oak trees on the property,  owing to the fact that "they've got wires holding them together".    Go figure.

73/n2ea