Force 12s Tapering may have solved low wind speed resonances, However I have
a broken shortest 10m Director on a C31XR-H which was rated at 135mph. That
broke at the junction of the 5/8"and 1/2" tube at wind speeds of 80-85mph.
At the time I stood under the tower and could hear the another (probably
10m ) also in mechanical resonance so this problem still exists. It has just
shifted higher in wind speed. F12 don't suggest rope mainly because of ice
loading. However I will have to do something to upgrade my C31 otherwise I
can expect it to break again.
73 Clive GM3POI Still thinking about extra tubing/rope.
----- Original Message -----
From: <K7LXC@aol.com>
To: <ve3tu@rac.ca>; <towertalk@contesting.com>
Sent: Monday, March 26, 2001 3:27 PM
Subject: Re: [TowerTalk] rope in elements
> In a message dated 3/23/01 3:13:22 PM Pacific Standard Time, ve3tu@rac.ca
> writes:
>
> > I was wondering if any one on the reflector has any
> > comments about the pros and cons of putting rope in beam
> > elements. It seems that the tips are always the first part
> > of the beam to self eject. I tried an elements with and
> > without rope and there was a slight reduction in vibration
> > with the rope (spinning an element by hand) es just
> > wondering if there is an other benefit.
>
> With conventional yagi design, the element taper was gradual. The
> reasoning was that you make the elements stiff and strong. Since the
element
> pieces were all 'about' the same size, they would self-resonate in light
> winds. Since the result was that the elements would spend a LOT of time
> vibrating, they would eventually crack and break or shed pieces. The rope
in
> elements was a successful way to dampen this light wind vibration.
>
> Force 12 changed this paradigm when they came out with their
aggressive
> taper schedule. The element starts out reasonably fat and tapers real
quick.
> This eliminated the element vibration and the need for rope in the
elements -
> two very worthwhile goals. So now the thinking is "bend like a willow"
rather
> than "break like an oak". It also has been shown to be useful in icing
> conditions - the elements droop like crazy with an ice load but then
> straighten right out with no damage when the ice melts.
>
> Cheers, Steve K7LXC
> Tower Tech
>
> --
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>
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