Topband: verticals and rope

[Larry Molitor]

Quite a few replies were received both directly and on the list offering 
comments and suggestions regarding my problem with guy ropes and the tubing 
vertical. It would seem that a little more info is in order.

Before I built this vertical I didn't belive you could put up a 90 foot 
tube without a crane. After a lot of encouragement and coaching from W7LR 
and N6RK last year, I went and did it! Rick has an excellent "how to" on 
his web page at:

http://www.n6rk.com

My vertical is similar to his with some differences due to locally 
available materials. I used 40 feet of 4 inch diameter 0.070 wall tube for 
the bottom, spliced to 30 feet of 4 inch 0.050 tube. The top 20 feet is 3 
inch 0.050 wall tube. Guy points are approximately 22 feet, 43 feet, 65 
feet and the top. I used compression type clamps for the attachment points 
so that I could adjust the actual location of the guys to reduce mechanical 
resonances. When I get time, I'll put photos up on the web page.

I first erected the thing using baling twine for the guys. Twine is very 
strong and very, very cheap. This allowed my to cheaply cut and try the 
actual guy lengths without breaking the bank. After I had it figured out I 
replaced all but the top guy (still was adjusting the top hat!) with 
"antenna rope".

The rope I purchased from Davis RF. It was labeled "dacron rope" on their 
web page. The spool was marked "Double Braided Polyester". I later found 
out that "Dacron" is a polyester polymer fiber manufactured by DuPont for 
use in many different applications. It would seem that some people use the 
term "dacron" to describe rope made from polyester fiber from other 
manufacturers.

Don't confuse polyester with polyethylene or polypropylene. These materials 
are not suitable for this application.

Some suggested "Phillystran". Phillystran is the name of a company which 
manufacturers many different kinds of rope. I assume they meant the type 
with Kevlar in it's construction. Some suggested Kevlar. But Kevlar will 
deteriorate in direct sunlight, so it's normally wrapped with, guess what, 
polyester! The high cost of this material will prevent it's use at this QTH!

I used 1/8 inch rope. I calculated that it would be well within it's break 
limits but I neglected to allow for stretch vs. stress. OH2BO hit the nail 
on the head when he suggested the rope must be well oversized to prevent 
stretch problems.

I will try again with 3/16 diameter rope (dacron/polyester) but it is 
available in both double weave and single weave. Any ideas which would be 
better?

The permanent top load wires will be stainless steel aircraft cable AFTER I 
figure out how long they need to be.

73,

Larry - W7IUV