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.
Steve K7AWB Spokane
--- K7LXC@aol.com wrote:
> In a message dated 9/2/03 1:53:54 PM Pacific
> Daylight Time,
> stetrekve@yahoo.com writes:
>
> > This topic has probably come up countless times
> before
> > but I am on the verge of making a decison this
> week
> > for my installation. I will have a M2 2M5WL 2
> meter
> > beam (17 element, 33' boom, 13 lb), the M2 6M7JHV
> 6
> > meter beam (7 element, 33' boom, 17 lb), and a
> Force
> > 12 C31XR on one mast out of Rohn 25 at 85 feet.
> The
> > tower is guyed per the Rohn book for the next
> wind
> > area above my location (which is the lowest wind
> > rating of 70+ MPH). I made the tower fulfill the
> > specifications for the next higher wind loading.
> >
> > The mast will be into the top section about 6-7
> feet
> > with a M2 2800 rotator and and TB3 thrust bearing
> at
> > the top. The total mast length will be 24 feet
> long
> > to extend 16" or so out of the tower to separate
> the
> > three beams from each other. The C31 will be one
> foot
> > above the top of the tower so only the two
> lighter
> > weight beams will on the unsupported mast.
> >
> > I have this 24 foot steel mast of 2" OD and about
> 0.2
> > wall thickness of unknown origin (type,
> specifications
> > unknown). It weighs 98 lb. To lower the total
> weight,
> > I am serious thinking of the following.
> >
> > Does anyone have a problem with me using a 24
> foot
> > mast of 6061T6 aluminum, 2" OD, 0.25" thick wall?
> The
> > less weight will mean an easier time of shoving
> up the
> > mast with each antenna being put on and less
> weight at
> > the top of the tower. Both VHF antennas have a
> dacron
> > rope to make the ends even with the center.
>
> The antennas up on the mast are relatively small
> so the bending moment
> they exert on the mast vis-a-vis your low windspeed
> rating is also relatively
> small. The aforementioned aluminum has a yield
> strength of 35,000 psi.
>
> Give me the square footage and spacing of the
> VHF antennas and I'll run
> my MARC (Mast, Antenna, and Rotator Calculator)
> Program. My educated guess is
> that you'll be okay.
>
> Cheers,
> Steve K7LXC
> TOWER TECH
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