[TowerTalk] Max height of aluminum tubing mast?

[Richard (Rick) Karlquist]

The most important property for masts such as this is stiffness,
which is proportional to OD^4 - ID^4.  Thus, 3 inch irrigation
pipe with 0.050 wall, which has approximately the same aluminum
content, is much stiffer.  It is easy to make a 75 foot vertical
from irrigation pipe.

If you somehow manage to erect a vertical with the tubing you
mentioned, it might wiggle around a lot in the wind.  This
can result in a metal fatigue over time, resulting in failure.
I'm not sure you can put enough guying on it to keep it from
wiggling.

Rick N6RK

Brian Machesney wrote:
> I need some help from the more structurally-oriented members of our
> fraternity.
> 
> I need to know if it is practical to erect a 75-foot vertical element from
> aluminum tubing that has the following dimensions:
> 
> OD: 1.785"
> ID: 1.57"
> Wall: 0.11"
> Length: 48" overall; 3.25" suaged and shouldered to fit into the next
> section
> Weight: 2.7lb
> 
> I have devised a raising fixture that has allowed me to raise 45ft masts of
> this material alone and with ease. Will a 75ft element stand up, or is there
> serious risk of it buckling under its own weight? Of course, numerous guy
> levels will be needed - I'm planning on 5.
> 
> Thanks,
> 
> Brian K1LI
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