With 17ft of mast exposed, how much is in the tower? I have always been one
to have close to half of the mast "in" the tower. I have a 21 ft .025 inch
wall mast and 8 ft of it is in the tower - so 13 ft is above. I have a 3 el
40M3L (32 ft boom) 10 ft above the tower with the last 3 ft for the boom
truss assembly. I have a 4 element wide-spaced 10M yagi just above the
tower (24 ft boom). I have never had anything of concern with this
arrangement.
I have a Thrust bearing at the top of the tower and the rotor (Yaesu 2800)
at the bottom of the mast. I have a second thrust bearing mid section but I
let it float unless I am doing maintenance requiring pulling the rotor.
I think the moment arm of the mast vs what's pushing against it in the tower
is a big part of the question.
Ed N1UR
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