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Author Topic: Kevlar or Dacron for guy-rope?  (Read 1804 times)
VA3GUY
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Posts: 172




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« on: June 07, 2013, 01:24:09 PM »

Simple question.  Which and why?

73,

- Guy
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AA4PB
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Posts: 12638




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« Reply #1 on: June 07, 2013, 01:41:18 PM »

Simple answer - It depends  Grin

Kevlar is strong but it deteriorates rapidly if exposed to UV from the sun. It is usually covered a black PVC to protect it. It is most suited to a permanent installation requiring strength, like tower guys.

Dacron is not so strong but is probably better suited to temporary installations, the end supports on a dipole, pole support guys, etc.
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K2DC
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« Reply #2 on: June 07, 2013, 01:46:38 PM »

Agree that it depends on what you want to do.  Dacron will stretch while Kevlar is resistant to that.  Dacron is more UV resistant than Kevlar, but Dacron over Kevlar is out there as well.  My choice would be Dacron for wire antennas, Dacron covered Kevlar for guys.

73,

Don, K2DC
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WB6BYU
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Posts: 12974




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« Reply #3 on: June 07, 2013, 02:27:24 PM »

Even that it depends on how much strength you need in your guy ropes.  Most polyester
(including duPont's trade name Dacron) is strong enough for a lot of uses, and has
excellent UV resistance.  Modern nylon ropes aren't that bad, either:  I had some very
old stuff that decayed in the sun, but most of the new stuff has UV inhibitors in it so
should easily last 10 to 20 years.

I'd only use Kevlar when I needed the utmost strength, and then I'd use choose something
with an outer braid of polyester or nylon to protect the Kevlar fibers.  (Note that Kevlar is
used in bullet-proof vests, they are NOT knife-proof.  The fibers cut easily and can lose
strength through abrasion, etc.)
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KE3WD
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Posts: 5694




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« Reply #4 on: June 07, 2013, 04:55:50 PM »

In my experience, Nylon tends to stretch too much. 
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N4NYY
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Posts: 4742




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« Reply #5 on: June 07, 2013, 05:21:21 PM »

I have used Dacron on guy wires and dipole legs.
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VA3GUY
Member

Posts: 172




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« Reply #6 on: June 07, 2013, 08:19:22 PM »

I have a Cushcraft A3S with the 40 meter add-on kit that I am going to be refurbishing it this summer.  The 40 meter kit uses a Dacron guy-rope to hold the driven element in place.  It's looking pretty old so I thought I might use some Kevlar rope I have.  It is 1000lb test but is yellowish in color (although it is new) so I don't think it has any coating.  Based on remarks and suggestions, I don't think it would be wise to use it up there.  So, I guess I will search out some more Dacron.

Thank you all...

73,

- Guy
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VA7CPC
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Posts: 2354




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« Reply #7 on: June 07, 2013, 08:41:10 PM »

It sounds like you have unprotected Kevlar.  Lifetime, in the sun, will be measured in months.  Maybe a few years, in VA3 country.

There's Kevlar-core, dacron-covered antenna rope here, specifically recommended for holding beam elements.  It'll last much longer.  Lower wind resistance than Dacron of equal strength:

http://radioworks.com/

.             Charles
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