[TowerTalk] antenna mast guidelines
jimjarvis at optonline.net
Mon Mar 23 19:42:14 PDT 2009
An interesting discussion... regarding mast loading, and how much
above the tower, versus inside....
" ... so going much above the top of the tower
can add considerable force to the top of the tower."
Doesn't it matter whether we're talking about a flat-top tower with
thrust bearing, or
a sleeve-topped tower? Is the load rating any different for the
(I'm no longer sure, but I thought the original question actually
dealt with the strength of
the mast material, itself, rather than loading on the tower, or on
the rotor. All of
those factors are relevant, in engineering the entire system, of
My real question: Is there any specific load rating for taper-top
25g which would
limit the mast extension above the tower top?
I'm contemplating running 20' of 2" x .250" 6061-T6 above 40' of
25g. 4' of mast would
remain in the tower, either attached via rotor, or via tb-3 and
accessory shelf. I might put
a 6m yagi or a small 20-10 lpda on top. In the latter case, I would
need to calculate the
windload on the log, and lower the structure appropriate to the
bending moment imposed
at the top of the tower. Will need to get structural data on the
mast, to determine what it will
If any ME on here happens to have data for 6061, 2" x .250", I'd
welcome the info.
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