To be very technical airplanes are work hardening and stress cracking
and breaking down that is why there is a maximum hour limit on the
airframe. The antenna is work hardening too, but the cost of inspection
and the availability make it a unlikely candidate for x-ray or dye
penetrating sprays for inspection. The strength to weight ratio make
them difficult to just give a visual inspection, by the time failure is
visible to the naked eye it has already fallen.
Randy
AC7NJ
-----Original Message-----
From: owner-towertalk@contesting.com
[mailto:owner-towertalk@contesting.com] On Behalf Of Bill Coleman
Sent: Monday, February 11, 2002 1:57 PM
To: Stephen Vinson
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Universal Freestanding Tower
On 2/7/02 9:09 PM, Stephen Vinson at kd4wiw@ipass.net wrote:
>Not having read all the post, and I'm not looking to stir up a cans of
>worms. But aircraft aluminum is a special alloy that is already
hardened and
>stressed.
Depending on the aircraft, the typical alloys you find are the garden
variety 6061-T6, 2024-T3, etc. Certainly nothing more exotic than
7075-T6.
6061-T6 is the most common structural aluminum manufactured. Common as
dirt. You're just as likely to find it in lawn furniture as aircraft.
>Aircraft also must under go annual inspections to look for stress
>cracks and failures. Proper inspection of aluminum as well as steel
towers
>is a constant necessity.
I believe this is my point -- proper ANNUAL inspection could probably
avoid many tower failures, regardless of material.
If aluminum were subject to extensive hardening and sudden failure -- it
would be immediately disqualified as an aircraft building material.
Come to think of it -- why don't all those vibrating aluminum ANTENNAS
work harden and break, eh?
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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