[TowerTalk] Homebrew tower

[Roger (K8RI) on TT]

I would be careful adding extra braces.  Much of the brace strength 
comes from the angles between the brace and legs.  Using lesser angles 
reduces the strength, requiring still more braces.  OTOH. I doubt the 
extra braces would cause the tower to collapse under its own weight.

The braces serve to keep the tower legs parallel, which adds a lot of 
strength in the lateral plane (resistance to bending in the wind) It 
adds little to the ability support a load.  IE: dead weight. They also 
keep the tower from bending when "tipped up" in one piece.  I believe 
"X" braces bolted, or welded together where they cross will add strength.

This tower is only going to be about 40 to 50 feet tall and will support 
a small beam/tri-bander.  I have my doubts about the wind load  and 
leverage from a mast supporting a 5L 6-meter Yagi and a small 40 meter 
beam at the required spacing.  I'd be more inclined to use a series of 
sloping dipoles on 40 and limit the wind load to a single, small tribander.

I'm assuming that the limitations are materials and budget as they are 
for most hams and suitable used towers are not available.  That adds 
another dimension to the requirements: Durability.  To me, it sounds as 
if failure of the tower is not an option.  Here in the states, we have 
the options of used towers and lots of suitable materials to build and 
rebuild towers.   This does not appear to be such a case.  If budget is 
the problem, then I'd go conservative on the antennas.

73

Roger  (K8RI)




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