[TowerTalk] Nonconductive guys
tgstewart@pepco.com
tgstewart@pepco.com
Tue, 16 Mar 1999 15:26:24 -0500
I put together the original PVRC group deal on the fiberglass from Polygon.
It was a very trying experience, let me tell you!
I also concluded as others have that they really dont know anything about
using it for guys.
Regarding the cracking, etc., I am fairly certain that this is purely
related to heat exposure and the stress of being in a relatively tight
coil. All the stuff I ordered was black, thinking that it might hold up
better in the sun (like black polyrope seems to do better than white or
yellow) and might be less visible in certain cases. Of course, black is
the worst color for absorbing sunlight as far as heat is concerned.
Leaving this stuff coiled up in a tight bundle out in the hot summer sun is
sure death. The polyester resin they use gets soft as it heats up. When
it's in a coil, the glass fibers toward the inside are in compression and
the outside in tension. Since fiberglass is excellent in tension and not
too good in compression, the first thing to happen under repeated heatings
of the resin is that the inside fibers start to buckle or bow out. Glass
fibers are very brittle, so before long the inside ones start mushrooming
and snapping. As this weakness occurs, it puts more and more stress and
bend on the fibers that are left. Eventually the whole thing is broken.
Note that this could also happen with any other color material if they
cover it in the black corrugated drain pipe they used around mine for
shipping.
Bottom line: Do not leave coiled fiberglass laying around in direct
sunlight or any other place it could get extremely hot. As suggested, it's
a good idea to uncoil it as soon as you get it in...usually just laying it
out along a fence line or around the yard in some large coils.
I've got two tower with it now and so far no problems at all once its up.
It's nice like Phillystran in that it is extremely light, so handling long
guys isrelatively easy and there is litte sag when you are done. 3/8" rod
weighs about 1 pound per 10 feet, and the Polygon PGP504 which is what I
purchased calculated out to about 13,000 lbs tensile strength, which is I
believe just slightly better than the equivalent steel. Once you figure
out how much you can save on insulators and the associated grips on long
runs of this stuff, it looks extremely attractive. Totally nonresonant,
light, fairly inexpensive, and easy to handle once uncoiled.
The bad part is mainly that it is fragile. Tensile strength is great, but
it's a relatively soft material and wont tolerate any abrasion. Do not use
it anywhere near trees or anything else that might rub up against it. I
wouldnt want to be on the tower if a large heavy object fell on the
fiberglass. You will need vibration dampers: these are spiral plastic
rods that wrap around the guys and dampen vibrations that can build up
around any smooth round object. The are relatively inexpensive and also
available from PGP. It's also not nearly as safe around a fire, so you
should use steel for the first 15 or 20 feet above ground and then do the
transition to the fiberglass. Again, it shouldnt be used anywhere near
trees.
However, compared to Phillystran, which has most of the same concerns, it
is about 1/3rd the cost for a stronger product.
"Richard L. King" <k5na@texas.net> on 03/16/99 01:15:02 PM
To: Pete Smith <n4zr@contesting.com>, towertalk@contesting.com
cc: (bcc: Tyler G Stewart/BENN/CEC)
Subject: Re: [TowerTalk] Nonconductive guys/fixed side mount
At 01:01 PM 3/16/99 +0000, Pete Smith wrote:
>I plan to go over to totally non-conductive guys for the top set, and move
>my insulators down to the middle set. Question is, is Phillystran the
only
>practical option? A few years ago, some guys in PVRC bought a large
>quantity of Polygon(?) fibreglass guy rod, which I understand is only
about
>1/3 of the cost of Philly, but as I recall there were minimum quantity and
>handling issues. Can anyone enlighten me on this option?
Last year (summer 1998) I bought ten, 1000 foot, rolls of the Polygon 3/8"
fiberglass rod and we (Susan and I) have been slowly installing it on three
new towers over the past year. I paid $0.40/foot for it because I bought a
10,000 quanity. Lesser amounts cost more per foot and I don't remember
without digging out the files what it was.
PLP makes grips that attach to this size rod and even conducted a pull
tests for me. Many manufacturers produce fiberglass rod but only some are
aware of its use for guying and advertize it as such. Others, like Polygon,
are aware of this usage but guying is not a part of their sales pitch. The
rod is a combination of fiberglass, epoxy, and uv inhibiters that is
"pultruded" through dies to produce a product of a certain size (depending
on the dies).
If you search the internet, you will find many companies that makes
fiberglass rod with similar specs. The thing to watch for is the precise
measurements of the sizes and whether there is much deviation of size
during the pultruding process. You want to make sure that the grips won't
slip because you got a product that is too small due to deviation limits.
The Polygon product that I received had very good deviation control.
The rod comes rolled in 8 to 10 foot rolls. You need a team to unroll them
as one or two people might not be able to handle it. It has enough energy
to break teeth and maybe crack bones. The rolls want to become straight and
have to be carefully controlled. It wasn't that hard to unroll it but it
took at least three or four people here to do it smoothly.
It is best to unroll it soon (a few weeks max) after you receive it to make
sure no cracking or deformation occurs. If you have ordered 1000 foot rolls
then you need a 1000 foot long area to store it. And you should store it
where you won't run over it with a mower. That isn't good to do. Polygon
was willing to send me any length rolls that I wanted it in. I chose 1000
feet since I have the room to store it down a fence line here.
I have found it easy to cut the rod (I use a hacksaw) and to apply the PLP
grips. Standard 502 insulators are a good match for the grip loops. I
always have about 5 feet of steel cable at the tower end and about 25-30
feet at the anchor end with the fiberglass rod in between. This is to
prevent damage from possible falling objects on the tower and
groundfires/vandals on the anchor end.
So far the fiberglass rod is working out great for me. I know that W3LPL
has used the stuff for several years and may be able to comment on
long-term problems, if any.
73, Richard
k5na@texas.net
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