[TowerTalk] Mast Extentions

Fred Roberts froberts@pe.net
Sat, 29 May 1999 14:22:24 -0700

> However,  I am thinking about ordering a "chrome-molly"
> (if that is the correct term)   mast to increase the full-up
> height from about 55 feet,  to more like 65 or 70 feet.
> Assume a 20 foot long mast,  with 5 or so feet down
> inside the upper section of the MA-550?

> So,  my beam is "only" a C4.  Any ventures as to the size
> of mast,  if it is a reasonable idea,  to put atop the MA-550
> to lift the 39 lb.,  6.4 Sq. Ft wind load, and 18 foot boom C-4?


The impact of raising the antenna from 55ft to 70ft is to increase the
load on the tower windload from 6.4sq-ft to 8.2sq-ft (6.4 x 70/55) ...
it's is rather like adding a pipe to a wrench to apply more torque to a
stubborn nut).  Plus something like 2.6sq-ft for the added 15ft of
exposed mast  (I figured what added windload would be for each foot
added to the tower height and then added them together).  So, it seems
to me you go from a wind load of 6.4 sq-ft to 10.8 sq-ft.

If your tower can handle that and the lifting load of a new mast, it
seems like you are in business.

Fred Roberts, W6TKV
Riverside, CA

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