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Re: [TowerTalk] Heavy Duty Masting

To: towertalk <>
Subject: Re: [TowerTalk] Heavy Duty Masting
From: Dan Zimmerman N3OX <>
Date: Fri, 8 Apr 2011 21:06:57 -0400
List-post: <">>
> Next batch of tube I order is going to be stronger and harder than 6061-T6.

But it's not going to be [i]stiffer[/i] which is what you want if you're
worried about the sag when raising it.  The modulus of elasticity varies
very little across types of aluminum... different alloys have SLIGHT
differences but a quick sampling on Matweb suggests there's something like a
5% elastic modulus difference between, say, pure aluminum and expensive 7075

'Course if you tried to put up a pure soft aluminum mast the size of the one
you did, it would probably fold over in ten places... but that's because you
would have exceeded the yield stress.

Probably makes more sense to go BIGGER next time.  Tube stiffness goes like
the fourth power of the diameter.  2.5 inch tubing would be nearly 2.5 times
as stiff as  2 inch tubing... and even if it had a thinner wall it would
tend to be considerably stiffer.


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