Bill, NY3M, makes excellent points in favor of a BPC - pier pin base. I
have two 55G towers using this base system. What he says about getting your
tower to align with the guy points is very true and very critical to a
structurally sound system.
I elected not to use a straight section in concrete for some additiional
reasons:
I have a relatively high water table and can envision water rising inside
the tower legs to above the frost line and freezing in the winter, perhaps
splitting the legs. BTW, I've seen one tower constructed with a section in
concrete where the fellow did not let the legs extend below the concrete for
drainage. His tower legs held water that drained from above. The water
froze and split the legs just above the concrete base -- not a good situation.
When I look at commercial installations, I see them mounted on a bottom
section that tapers to a point. This arrangement or a pier pin arrangement
allows some motion at the tower base. With a base burried in concrete there
is no "give" to accomodate temperature changes or torque transmitted to the
base.
Also, if you ever move, just lift off the bottom section and away you go.
No cutting torch, etc.
73 -
Ralph - K0IR
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