AA4LR wrote:
>>There is a big difference between "don't exceed the manufacturers
>>ratings" and "buy one heavier than you need". The problem with
>>aluminum is that it work hardens. If you load it near it's initial
>>max ratings, wind gusts over the years WILL cause it to fatigue and
>>de-rate, and eventually fail.
>Gosh, you're right, that's why aluminum airplanes are life-rated to only
>so many flights or years. Right?
>
>I'm sure many aircraft owners are still waiting for their 50+ year old
>airplanes to "work harden."
>
>Without proper maintainence, any structure will fail, even steel ones.
>
>Aluminum towers, properly loaded and properly maintained, should last
>just as long as aluminum aircraft.
Did I say that aluminum doesn't have good uses?
Airplanes are obviously well engineered. The history of aluminum
towers - judging by how many of them that have ended up laying
on the ground - is not so good. Things that fly need a high strength
to weight ratio, which aluminum provides. Cost is a secondary
concern.
Most prospective tower owners, especially in the commercial
market, consider strength & longevity vs cost to be more important
than weight issues. Therefore, virtually all commercial towers
are steel.
There's nothing wrong with a well engineered aluminum tower, skyscraper,
suspension bridge, or freighter - except cost.
--
Steve K8LX
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