jim Jarvis wrote:
> The N7NV analysis is impressive.
>
> Tower deflection is attributed largely to guy stretch.
>
my 100', 45G with30' of mast out the top holding a TH-5 tribander at
100', 7L C3i 6-meter antenna at 115' and a cross boom at 130' holding 2,
11L 44 and 2 12L 144 antennas. The top of the mast with the 4 antennas
looks like a bluegill flyrod that just tied into a record breaking
bass. A transit only shows a couple of inches of tower movement. 6000#
test Phyllistran at the top with 4400# test at roughly 36 and 70'
tensioned to 600# and 440# respectively.
73
Roger (K8RI)
> I've been on top of 80' sailboat masts, which are intended to be
> flexible at their
> top... which don't flex more than 1-2" under peak loads. (yes, I've
> been up there
> to free a fouled haliard, under load, pitching and rolling.)
>
> I'm wondering if guy stretch is permitting 45g to move by almost a
> face width @ 100',
> if perhaps we aren't tensioning the guys adequately. To be sure,
> we tension the
> bejeezus out of boat shrouds and stays. You don't want the mast to
> pump and
> dissipate energy, you want the energy peaks to translate to boat motion.
>
> In the case of tower flex, that will tend to load-shed, making the
> structure less
> susceptible to peak load damage. So it's not a bad thing.
>
> I'm still feeling dissonance between my intuition and the analysis I
> just looked at.
>
> n2ea
>
>
>
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