I have a MA-40, I can't help with the calcs but cranked down mine has
survived 90+mph winds with a 15 foot mast with a stacked pair of 5 element
6m beams that have about 3 sq ft of windload each.
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of Alan C. Zack
Sent: Monday, March 01, 2004 8:33 PM
To: Tower Talk
Subject: [TowerTalk] Wind Calcs for a U.S. Towers MA-40
I have run into a situation with my Building Dept in my attempts to
get a building permit for a U.S. Towers MA-40. I have moved to a
countryside QTH and wish to put up a small tower. The city building
code allows me to have a 45 ft tower with no variances. Over 45 ft I
would need a variance.
I choose the MA-40 because it will crank down to 21 ft and can be
folded over at the base to work on the antenna. It has a freestanding
base. My yard is not very large and so the need for the crank down.
I would rather not climb the thing and so the hinged base. I don't
have room in the yard for guy wires. The MA-40 tubular tower seemed
ideal for my situation.
Now the problem. I took the U.S. Towers drawings and wind calcs to my
building dept. U.S. Towers originally submitted wind calcs under
UBC-97. The Bldg Dept wanted IBC-2000 calcs for 90 MPH. The U.S.
Towers PE states IBC-2000 wind calcs are that it can handle a 3.5 sq
ft antenna at 70 MPH, but at 90 MPH it cannot even support itself at
that high a wind. I can live with the 3.5 sq ft antenna by using a
Cushcraft MA-5B to keep a small, clean tower and antenna. But what do
you do when a self supporting tower can't handle a 90 MPH wind calc?
Is the 90 MPH requirement unreasonable? Can anyone suggest another 40
or 45 ft crank-up tower with a hinged base that would pass a 90 MPH
wind calc?
TIA for any ideas.
--
__________________________________________________________________________
Alan Zack
Amateur Radio Station K7ACZ
Las Vegas, Nevada, USA
Quality Engineer, The Boeing Company, Retired
Aviation Chief Warrant Officer, U.S. Coast Guard, Retired
U.S. Coast Guard, Always Ready, Always There
Every hour, Every day, Around the Clock and Around the World
SEMPER PARATUS
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
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