[TowerTalk] Concrete base for self-support tower

[Dave]

G'day all:

I need some advice.

I'm digging holes for bases for two towers I plan to install at my new
location.  These towers are 48ft self-supporting towers manufactured by
Delhi in Ontario, similar to Rohn's old BX series of self-support towers.
Delhi's specifications for the base recommend two cubic yards of concrete in
a 4ft by 4ft by 4ft hole in the ground.

The ground under one prospective tower is quite rocky (Newfoundland is
nicknamed "Da Rock" for a reason), and the other is both rocky and wet.
It's darned hard digging, and because these towers are going into a very
dense forest, impenetrable to a backhoe, the digging has to be done by hand.
I am at the point in one hole where the pick just bounces off the rock.
Because the other hole is both wet and gravelly, digging goes very slowly.
I'm looking to cut some corners, but I need to know how inadvisable this
corner-cutting might be.

My questions are:
- If I made my bases wider, say 5x5x3ft deep (more concrete by weight and
volume, but not so deep), would this acceptably approximate what the
designers had in mind?
- if I stuck to the original design idea of a 4x4x4ft base, would it be
acceptable for any of that base to be above the soil?

I plan to install KT34s on each of these towers and put up some wires.  I
dare not put these towers up any higher than 48ft, as we have extremely
strong winds here.  Besides, I'm 2km from the Atlantic and I'm pretty
confident I'll do well from here even with shorter towers than I would
prefer.

Dave VO1AU (ex-VE2ZP)