[Towertalk] Antenna Wind Area Calculation

[EUGENE SMAR]

Roger:

     I have a GP-15 on top of my mast.  I couldn't find area figures either
so I calculated it myself.  The fiberglass covering is about seven feet tall
and 3/4 inch diamter.  "Shadow area", therefore, is 84 X 0.75 = 63 sqin /
144 =  about 0.5 sqft.  Multiply by the shape factor for long cylindrical
objects in a wind stream (here comes the controversy!) of 1.2 and you get
about 0.6 sqft.

     If you want to antagonize yourself, measure or calculate the "shadow
area" of the KT-34 elements and boom and traps  (Length X diameter for each
trap and section of tubing)  and see if you come anywhere to that 6 sqft
figure that the manufacturer advertises.  This reflector ran through a
series of postings last summer (and possibly many times previous) on just
what do these wind area dimensions found in spec sheets mean.  I'm not sure
we ever settled the issue; in that case I just recalculated my antennas'
figures as above (a very conservative approach) and used them in my
tower/mast design.

     I sleep well as a result.

73 de
Gene Smar  AD3F
BTW my tower is a self-supporting Trylon T-500-64, rated at 45 sqft (???) of
wind loading within two feet of the tower top.

-----Original Message-----
From: Roger Hackler <rhackler@mindspring.com>
To: towertalk@contesting.com <towertalk@contesting.com>
Date: Thursday, November 21, 2002 12:42 PM
Subject: [Towertalk] Antenna Wind Area Calculation


>Hey TTers:
>
>I'm in the process of calculating the required tower windload rating I need
>to consider when purchasing a new tower.  This will be a simple
>installation, probably in the 50' range.  Due to XYL RFI, freestanding is
>the option available, and I want to be sure I select a tower that will
cover
>my planned antenna load, with room for future expansion possibly.
>
>Planned antennas include my old trusty KT-34, which has a 6 square foot
wind
>area according to the original documentation.  I am planning to upgrade it
>to the M2 version before I hang it, and am not sure if a wind area change
>occurrs with the upgrade, but that should be easy enough to track down.  I
>also plan on my Comet GP-15 Vertical, which I can find no wind area
>information on, as well as my B&W folded Dipole near the top in Inverted
Vee
>configuration.
>
>Initially, I plan to keep the KT-34 near the top of the tower, but would
>like to have the leeway in the tower rating to add a 6 meter yagi above the
>kt-34 in the future. I am in a 70 MPH county.
>
>How do you factor in the vertical and the wires?  I realize this is
probably
>a dumb question, but one of the things I love about this hobby is dumb
>questions are OK!
>
>Thanks in advance!
>
>73 de KN6RO (Formerly HL9AX in a different life :)
>
>
>
>
>_______________________________________________
>AN Wireless Self Supporting Towers at discounted prices,
>See http://www.mscomputer.com
>
>Wireless Weather Stations now $349.95. Call Toll Free,
>888-333-9041 for additional information.
>_______________________________________________
>Towertalk mailing list
>Towertalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk