[TowerTalk] aluminum mast again

[K7LXC at aol.com]

In a message dated 9/2/03 3:22:40 PM Pacific Daylight Time, 
stetrekve at yahoo.com writes:

> Thanks for the reply.  The 16" should read be 16 feet
>  for the approximate mast out of the top of the tower.
>  The 2 meter antenna is: 2.7 sq ft
>  The 6 meter antenna is: 2.5 sq ft
>  The Force 12 C32XR is: 10.7 sq ft, weight. 82 lb
>  Force 12 HF beam 1 foot above top of tower.  6 meter
>  beam 6 feet above HF beam and 2 meter beam 6 feet
>  above the 6 meter beam.

Hi, Steve --

    The bending moment is 18,641 in-lbs. The mast recommended needs a yield 
strength of 42,000 psi and 0.188" wall. 

    Since the yield strength of the of 6061-T6 is 35,000 psi, you're pretty 
close to a potential failure. One thing you can do is to move the antennas 
closer together. Or go to a steel alloy mast. Or put a piece of steel inside the 
bottom of the mast to strengthen up the place where it's going to bend - right 
at the thrust bearing. 

Cheers,
Steve     K7LXC
TOWER TECH 
Champion Radio Products