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[TowerTalk] Gin Pole Rope Length

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Subject: [TowerTalk] Gin Pole Rope Length
From: (Jim White, K4OJ)
Date: Tue, 23 Jun 1998 00:58:43 -0400
Double you two double cross states:

"Make sure you buy a continuous length, long enough to go up and
down your entire tower, plus 5-10% for working on the ground."

I STRONGLY [that's emphasis added] disagree..........

If you are using the rope for such activities as the tramming of yagi
antennas, the length must be long enough to go vertically up to the high
spot  [top of tower mast] and must also be long enough to come down to the
ground AT AN ANGLE......and if you want to take the pull/down rope out away
from the tower through a pulley there is a horizontal length to add, too.

Geometry again, boys and girls...

So....if you have a 100 foot tall mast, and you are tramming from a point
which is significantly farther out than your guy points are to aid in
avoiding the dreaded top set (I say significantly because there is always a
"sag" in the tramming line's path) .....then lets say then for example that
you launch your yagi from 100 foot out, your rope needs to be:

on the angle: prox 141 ft [square root of two is abouts 1.414] 
+ (100 ft vertical) 
+ (horizontal pull rope - say 20 feet)

So, your rope should be at least 2.61 times the height of your tower! 

"Buy your main rope three times as long as your tallest tower's mast is
high and be comfortable with it"   
(AKA OJ's Theorem)

[I like K5RC's garbage can idea for storing of rope.....hopefully my
neighbor will not get wise to my scheme to abscond with his "wheeled"
Rubbermaid product]


Jim, K4OJ

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