I am using Dynamix for guying my 150 feet tower with 2x3 el full size 40m
yagis and 4 large tribanders. Dynamix is a combination of Dyneema SK75 and
Aramid fibres (Kevlar) used in yachting. The high strength of both fibres is
blended with the low creep under constant load of Aramid, and the high
resistance to flex fatique of Dyneema. There is polyester outer cover on it
to protect the Aramid content from UV.
I use 10mm Dynamix that has breaking load of 4000 kg! I have about 25m of
upper and 15m of lower guy wires from the top of Dynamix, steel wires with a
few isolators after that to the ground. Tower is guyed at two levels.
They have held up perfectly for more than 3 years now with small creep that
has made me tighten the guy wires once I guess, no problem.
Dyneema (called Spectra in US) is in many ways superior to Kevlar:
Dyneema is stronger (higher breaking load)
Dyneema lasts longer
Dyneema weights less
Dyneema resists much better to UV light
Dyneema has lower dielectric constant (about 2.2 vs 3.8 for Kevlar)
Dyneema has excellent abrasion resistance, low moisture absorption, very low
elongation, excellent flex fatigue resistance
Two negative aspects are:
Dyneema has lower melting point (c.a. 150 degrees C vs 400 for Kevlar)
Dyneema exhibits something called CREEP -non-recoverable elongation when
constant load is applied for long time...but for late models and thicker
ropes this is almost nonexistent
Dyneema is UHMWPE that stands for Ultra High Molecular Weight Polyethylene.
Fibers are made from this material by AlliedSignal (SpectraR), DSM
(DyneemaR), Tenfor (SniaR), and Mitsui (TekmilonR). The molecular formula
for this polymer is the same as common polyethylene, but is significantly
different because of the very high molecular weight, from 10 to 100 times
higher than commercial polyethylene molding resin.
----- Original Message -----
From: "W4ZW" <email@example.com>
To: "'Roy Thistle'" <firstname.lastname@example.org>; <email@example.com>
Sent: Sunday, January 08, 2006 8:02 PM
Subject: Re: [TowerTalk] Guyed Tower with Dyneema rope guys
> Dyneema is great stuff. Many "A Class" catamaran sailors use this for the
> forestays to the mast. These are the two lines that hold the mast to the
> forward points of the two hulls. It is under enormous pressure under sail
> especially under the forces of a reach or when sailing close hauled. I
> regular steel stays on my catamaran, mainly because I made them before I
> knew about dyneema. I do use dyneema for the lines on my spinnaker, and
> splice in a more manageable (by hand) larger sheet on deck. Dyneema is
> very easy to work with and I've used it here to support the center and
> ends of a wire array, which is either a full wave 80M loop or a 80M
> Windom . It has been up there in the Florida sun and through three
> hurricanes over the past 4 years and still looks good. I check it every
> year, and still don't see the need to replace it.
> Great stuff, tiny and flexible, yet very strong.
> Jon Hamlet, W4ZW
> Casey Key Island, FL
> "A little piece of paradise in the Gulf of Mexico"
> TowerTalk mailing list
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