[TowerTalk] polyrod

[Jim Lux]

And, I'll add some of my own experience.  I've built a fair amount of stuff
with structural steel, structural aluminum, and pultruded fiberglass (Extren
550). From a strength standpoint, the aluminum and Extren are about the same
(in bending, tension, compression, but not shear.. Fiberglass is quite weak
in shear).  However, the Extren is about twice as flexible as aluminum (that
is, a 2x2" box tube of aluminum will bend about half as much as the same
size tube in Extren, with a "less than failure" load.

Aramids are substantially stiffer and stronger than glass fibers (in
composites, the resin just keeps the fibers in place, and doesn't contribute
to the strength).  However, that greater stiffness makes them more brittle.
You're not as likely to see a Kevlar/Epoxy spring as a Glass/Epoxy spring.


----- Original Message -----
From: "Michael Tope" <W4EF at dellroy.com>
To: "Jim Lux" <jimlux at earthlink.net>; "Roger K8RI on Tower"
<k8ri-tower at charter.net>; "Tom Rauch" <w8ji at contesting.com>; "RICHARD BOYD"
<ke3q at msn.com>; <towertalk at contesting.com>; "Ken Claerbout"
<K4ZW at Staffnet.com>
Sent: Saturday, April 30, 2005 8:11 PM
Subject: Re: [TowerTalk] polyrod


> I believe for the same tensile load, phylistran stretches more than the
> equivalent (same load
> rating) EHS steel guy. Kurt K7NV did some really interesting analysis on
> this:
>
> http://k7nv.com/notebook/towerstudy/towerstudy1.html
>
> And here is some specific information comparing the properties of steel,
> kevlar, and fiberglass
> guy material:
>
> http://k7nv.com/notebook/topics/guycable.html
>
> 73 de Mike, W4EF.................................................
>