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[TowerTalk] free mast software

Subject: [TowerTalk] free mast software
Date: Thu, 04 Jan 2007 14:35:11 -0500
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 For all of you mast users: Here is a link to spreadsheets to figure mast 
Download the Spreadsheet
Unzip it
Rename the .wk1 files .xls files if your PC doesn't know what to do with them
The numbers in BLUE you can change. Using "Mast2.xls" I put in these parameters:
Mat' l yield strength 35,000 (this is 6061-T6 aluminum)
Enter mast dimensions
Top   Diameter 2   Wall t in 0.25   Length in 240  
(set other mast dimensions to 0)
Enter antenna dimensions: 
El area 3   Bm area 3   Height in 240
"Calculates these parameters" kicks out the number 58 mi/h
In my previous email I calculated 72 mph (peak gust). The spreadsheet gives 58 
mph. I don't know if I made an error in my calculations or if the spreadsheet 
is allowing for gusting. I think the 58 mph might be the the number that the 
national weather service gives. There is a gusting factor to add to this and 
the spreadsheet might be doing it. 
Where I lived in Boise, Idaho this 2" diameter, 0.25" wall aluminum mast would 
survive holding 6 sq ft of antenna 20' above the bottom of the mast. Where I 
live now in Colorado the mast would not last a year. 
Changing the aluminum mast to chrome moly steel changes the yield from 35,000 
psi to 70,000. This is twice as strong and allows 1.4 times higher wind 
velocity. In this example the wind survival goes from 58 mph to 82 mph. 
Alternatively using an aluminum mast with a diameter of 2.75" and 0.25" wall 
gives a wind survival of 80 mph. This spreadsheet sure beats 
     Dave WX7G 
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