On Thu, 17 Aug 2006 08:25:28 GMT, Owen Duffy wrote:

On Thu, 17 Aug 2006 01:33:58 -0400, "Graywolf"
wrote:

Polyethylene and polypropylene ropes are rapidly destroyed in sunlight.

Barry,
The Wireman is another excellent source of antenna rope. Contact him at TheWireman.com.

Walt, W2DU

Excellent comparison. I'll abandon the wire rope idea and get some black
Dacron or polyester.

Thanks to all for your comments!

--
Bruce Wilson KF7K
http://science.uvsc.edu/wilson
"Graywolf" wrote in message
...
"Roy Lewallen" wrote in message
...
That would have been polypropylene, widely sold in hardware and DIY
stores. It rots in no time if exposed to UV. Polyester holds up very
well, and nylon is just about as good. (I think most of the rope sold
specifically for antenna use is polyester.) I'd use black rope if I lived
in an area having a lot of direct sunlight and/or one that's at at high
elevation, since this improves its UV resistance, but ordinary nylon or
polyester rope lasts many years at my western Oregon QTH. (Maybe the
moss/algae growth helps.) I like nylon because its stretchiness acts as a
shock absorber, but this would be a disadvantage for some applications.

Roy Lewallen

Polyester (Dacron) rope has the higher ultraviolet resistance. Nylon,
especially if formulated with UV absorbers and anti-oxidants does fairly
well too. If you get acid rain in your area, Nylon will not last nearly
as long.
Polyethylene and polypropylene ropes are rapidly destroyed in sunlight.

The mechanism that protects polyester from ultraviolet in sunlight is an
interesting one. When a short wavelength photon hits the polymer in the
rope, its energy has to go somewhere. Often it just heats the polymer,
but sometimes it breaks the polymer chain. Polyolefin ropes
(polypropylene and polyethylene) have an easily broken polymer backbone.
The backbone is much stronger in polyamides (Nylon). Polyesters, however,
have aromatic (benzene-like) structures in them that absorb the short
wavelength UV radiation and re-emit it as longer wavelength fluorescence.
In polyethylene terephthalate (PET, Dacron) this fluorescence is generally
in the near infrared so it is not visible. In polyethylene naphthalate
(PEN), the fluorescence is in the visible region. This polyester has
better barrier properties for food use and can withstand slightly higher
temperatures than the PET used in most plastic soft drink bottles and food
containers. But the fluorescence is unwanted in most food applications so
quenching agents are added to suppress this property.

Dacron is DuPont's proprietary name for their PET. Usually rope sellers
charge a premium for the name, but polyester fibers as used in ropes are
manufactured by many other companies. Roy is correct about the black rope
lasting longer. Carbon black added to the polyester is an excellent UV
absorber.

73, Barry WA4VZQ

Remove the NO SPAM to reply directly.

On Thu, 17 Aug 2006 08:03:20 -0600, "Bruce Wilson"
wrote:

Excellent comparison. I'll abandon the wire rope idea and get some black
Dacron or polyester.

Thanks to all for your comments!

The Wireman has uv-resistant Dacron rope.

bob
k5qwg

Tam/WB2TT wrote:

If you live anywhere near water, a boat shop might be a good source for rope
that will withstand weather and UV. Think of all the rope on a sail boat. I
haven't checked prices.

Ironically, polypropylene rope, the very worst kind for UV, is often
sold as water ski tow rope and for other marine applications, because it
floats. So check the label carefully.

A friend of mine once built an 80 meter vertical from PVC pipe, with a
wire inside or outside of it. Being an analytical sort of person, he
carefully calculated the wind loading, allowing for the 100+ MPH winds
not uncommon in his area of Colorado. Then he selected guy rope of the
required strength, with a hefty safety margin. It worked fine for about
6 months, then the antenna fell over on a day when there was only a
slight breeze. Mystified, he inspected the antenna and found that he
could pull the rope apart with his bare hands. That was when he, and I,
learned about polypropylene rope and sunlight. Of course, his location
at about a mile elevation and where the sky is clear 300 or so days per
year was a particularly harsh environment for plastic as well as for
fair-skinned people. I got away with using the stuff for a couple of
years here in western Oregon. But there are a lot better choices.

Roy Lewallen, W7EL

Welcome back to the group, Barry. I, and I know many others, really
appreciate hearing the straight story from someone who truly knows what
he's talking about. Thanks!

Roy Lewallen, W7EL

Graywolf wrote:

Polyester (Dacron) rope has the higher ultraviolet resistance. Nylon,
especially if formulated with UV absorbers and anti-oxidants does fairly
well too. If you get acid rain in your area, Nylon will not last nearly as
long.
Polyethylene and polypropylene ropes are rapidly destroyed in sunlight.
. . .

Roy Lewallen wrote:
Welcome back to the group, Barry. I, and I know many others, really
appreciate hearing the straight story from someone who truly knows what
he's talking about. Thanks!

Speaking of someone who truly knows what he is talking
about Roy, here's a technical question for you.

Given that a mobile antenna stinger has a VF of
approximately 1.0 so we can determine the approximate
number of degrees that it occupies and ...

Given that we can use EZNEC to determine the feedpoint
impedance of that stinger, it seems to follow that ...

We should be able to use a Smith Chart to determine
the characteristic impedance (Z0) of that stinger.

Yes, no?
--
73, Cecil http://www.qsl.net/w5dxp

Bruce Wilson wrote:
Of course it needs to last for decades or more in
the sun.

Like Roy says... good luck... Better be some really UV
resistant stuff if you want it to last decades.

As always, if you have suggestions that haven't occurred to me I'll gladly
listen to them.

Myself, I use antenna support *wire*. And that will last for decades.
But another reason I do that, is often I lengthen the antenna wires
for other bands. Fer instance, at the moment I'm using an 80 meter
turnstile, which are crossed dipoles, and also a 40 meter dipole,
all fed parallel with one coax. But two of the 80m wires can be
doubled to act as a 160m dipole, and also I have a set of jumpers
to use it for 20m. So by just changing the locations of the
insulators,
I can change things around according to season. I can have the present

setup, or I can have 80,40,20, or I can have 160,80,40. The latter is
the usual "winter" mode. My wires including the support wires are
so strong they will crumple the top section of mast before the
wire breaks. I had that happen when a large tree branch fell on a
leg in an ice storm. The wire didn't break. But it bent the top mast
section over, and I had to replace it. That was cheap though, as
I use an extra top mast section which is not part of the actual
telescoping mast. Sure, fresh rope is just as good, but it won't last
as long as the wire. Mine is insulated also, so that helps to prevent

corrosion. I don't see why it wouldn't work in a pully as long as it
didn't kink up on you.
MK

Thanks for the information, Owen.

"Owen Duffy" wrote in message
...

Polyethylene and polypropylene ropes are rapidly destroyed in sunlight.

Barry,

There is a type of rope known here as Silver Rope. I understand that
it is manufactured from UV stabilised polyethylene and claims
resistance to sunlight. It is also claimed to be resistance to most
acids and alkalis.

It is a very low cost rope, white in colour, and is widely used in
marine applications.

I have halyards and tails of this stuff that have been in the weather
for 10 years with no significant degradation (superficially or
observed when the strands are opened up).

Silver Rope is about half the price of Dacron rope (though only about
80% of the strength of Dacron). It takes knots well (as well as the
better synthetic fibre ropes, it has a slightly greasy feel), good
abrasion resistance and it is easy to splice.

Owen

Ultraviolet stabilizers can only do so much for polyolefin plastics. But
these plastics do resist acids and other chemicals very well. I suspect
this rope material contains a significant amount of titanium dioxide
pigment. Unlike carbon black which absorbs the ultraviolet, the titania
reflects it. What normally happens with polyolefins containing significant
amounts of titanium dioxide is that the surface degrades quickly leaving a
layer of the exposed pigment to reflect most of the ultraviolet, thereby
protecting the polymer underneath. In some cases, the oxidized surface
will hold moisture and conductive salts slightly reducing its insulating
and dielectric properties.

One reason polyester ropes stretch so very little has to do with how the
fibers in the rope are made. After the fiber filaments are extruded, they
are immediately stretched. This axially orients the polymer chain and
gives it a much higher strength. The same thing is done when making soft
drink bottles out of polyester. They start with what is known as a parison
(or preform) which is injection molded. This preform has the screw top
molded in. The bottom of the parison is heated in an infrared oven above
the polyester's glass transition temperature (around 90 to 95 C for
polyethylene terephthalate). It is then placed in a mold and inflated to
create the bottle shape, This inflation does bi-axial stretching of the
polymer backbone giving the bottle its great strength.

If you want to perform a simple experiment, take a PET bottle and hold its
neck or cap area with a pair of long pliers. Carefully pour boiling water
(100 C) into the bottle. This is above the plastic's glass transition
temperature. The bottle will shrink, much like heat-shrink tubing, but it
will not completely return to its original size. If you do this
experiment, be VERY careful as boiling water will spill out the top of the
bottle as the bottle shrinks.

I used to work in the research laboratories of Eastman Chemical Company.
Eastman made PET, PEN, PETG (glycol-modified PET, used in
microwave/conventional oven dinners), as well as polyethylene and
polypropylene. Some of their liquid crystal polymers would make excellent,
very high-strength rope, but the cost would be rather prohibitive for most
hams. I still have a large bag of fiberglass filled PET tensile test bars
from my days there. These make wonderful antenna and open-wire line
insulators.

73, Barry WA4VZQ

"Graywolf" wrote in message
...
I used to work in the research laboratories of Eastman Chemical Company.
Eastman made PET, PEN, PETG (glycol-modified PET, used in
microwave/conventional oven dinners), as well as polyethylene and
polypropylene. Some of their liquid crystal polymers would make
excellent, very high-strength rope, but the cost would be rather
prohibitive for most hams. 73, Barry WA4VZQ


I believe that Dacron is actually PET. At least that's what I read at
Wikipedia.

--
Bruce Wilson KF7K
http://science.uvsc.edu/wilson

"Bruce Wilson" wrote in message
. ..

I believe that Dacron is actually PET. At least that's what I read at
Wikipedia.

Dacron was originally PET fiber made by DuPont. It was their registered
trade name, but.is now owned by Invista. When Eastman Chemical Company was
still part of Kodak and still manufactured PET fibers, its trade name was
Kodel. Polyester fibers are made by a number of companies, each with their
own tradename. When referenced as rope, polyethylene terephthalate is
usually implied. However, other thermo-softening polyesters, such as
polybutylene terephthalate end polyethylene nalhthalate, are available.
Thermo-setting polyester resins, too, are found. These are commonly used
in fiberglass boats and some printed circuit boards although most printed
circuits use epoxy resins.

Quoting from the Invista website(www.invista.com):
"INVISTA is independently managed but wholly owned by a subsidiary of Koch
Industries, Inc. On April 30, 2004, subsidiaries of Koch Industries, Inc.
acquired INVISTA from E. I. du Pont de Nemours and Company. INVISTA,
formerly DuPont Textiles and Interiors (DTI), was merged with KoSa, a
producer of commodity and specialty polyester fibers, polymers and
intermediates. KoSa had been a Koch affiliate since 1998."

73, Barry WA4VZQ