Tom and Talkians:
You are absolutely correct. As long as you keep the
stress within the allowables, aluminum is fine and the
strength to weight ratio is better than steel.
Where the problems may occur, and it is again a function
of the design requirements of the system, is the
deflection of the aluminum mast versus a steel mast.
Since the modulus of elasticity for steel is
approximately 2.5 times as great as aluminum's. For a
given load with comparable section dimensions an
aluminum mast section will deflect 2.5 times more than
the steel mast section of same seciton dimensions.
For short mast cantilevers most likely not a problem.
However for large cantiliver distances maybe a big
problem.
Stress in a section is based on geometric section
properties and load. Deflection is based on stress and
elastic modulus. Be careful with long cantilever
distances say over 10 feet with large antennas.
Hank Lonberg. PE/SE KR7X
________________________________________________________________________
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Order online at http://store.eham.net.
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