[TowerTalk] Mast

[giw at bellsouth.net]

Someone please tell me if I am about to make a mistake. I plan to use a 20 ft.  long schedule 80 6061-T6 aluminum tube ( 1.9" OD .200 wall thickness)  for a mast on which I plan to put a Steppir 4el (9.7sqft) at 3 feet above the thrust bearing. The second antenna is a hygain rotatable dipole (2.8 sqft.) at 12 feet above the Steppir.  A windows program I have says this will produce a total of 21365 in-lbs at 70 mph. Data says that the 6061-T6 has a shear strength of 29700 PSI.  Am I drawing the wrong conclusion that this will work OK. Need some good old tower talk expert advice ASAP.  Thanks Van W4GIW