Barry Kirkwood PhD ZL1DD
Signal Hill Homestay
66 Cory Road
Waiheke Island 1240
----- Original Message -----
From: Pete Smith <firstname.lastname@example.org>
To: Barry Kirkwood <email@example.com>
Sent: Monday, 11 June, 2001 7:45 PM
Subject: Re: [TowerTalk] Guys and things
Baz, following from the Texas Towers web page.
"Phillystran is an electrically transparent nonmetallic guy cable which
offers complete guy line isolation, eliminating the need for insulators.
It's constructed of Kevlar® fiber, covered with an extruded copolymer
jacket which provides full UV protection."
I'm unaware of the basis for your comment about terminating Kevlar, but the
current best way of terminating Phillystran involves the use of PLP grips
similar to the big grips used on EHS. I don't see why that technique
should compromise its strength. The previous technique with Phillystran
involved "potted" end fittings filled with 2-part polyester (?) resin.
Again, why would such a termination compromise the strength of the guy?
To my knowledge attempts to use kevlar in standing rigging in sailing boats
have been abandoned due to chronic catastrophic failures at the terminations
or where the stays are other than a straight run. There may have been
progress, I am not up with the play these days. I assume that the demands of
tower guys are less critical than staying yacht masts.
Kevlar is well regarded for halyards, sheets and guys but there are still
problems with the terminations as it does not take kindly to small radius
bends. Hence they usually use them for limited time in serious racing.
The 502 insulators being discussed are about the size of two fists
together, weigh a kilo or better, and are designed to take 3000 kg or so of
tension. Not quite comparable to your electric fence egg insulators.
OK. I am not talking 3000kg loads.
A final aside -- most of the composite technology in all of the America's
Cup boats, including New Zealand's, comes from the United States.
True up to a point. A country with 3.8 million people and feeble industrial
development has certainly not invented carbon fibre etc. On the other hand
I would claim that there is considerable local expertise in applying these
materials to the manufacture of light strong sailing craft. No one does it
greatly admire the skill and tenacity of the New Zealanders in taking on
the world and winning, but it took the best technology money could buy, and
a lot of money.
The one boat NZ America's Cup defence and challenges cost a tiny fraction of
the US multi boat operations.
As for having the best technology in high modulus construction, soft foil
development etc., we plead guilty. The America's Cup rules have softened a
bit, but generally speaking the boats have to use home grown technology.
There is minimal buying in of technology from outside the country of origin
of any contestant.
But then, what was it someone said? "A boat consists of a hole in the
water, into which you pour money."
73, Pete N4ZR
No, no ... that's WEST Virginia
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