The MacAlba

The tower base becomes a real object.

Yesterday’s concrete pour transformed the hole in the ground into a real, honest-to-goodness block which, when cured, will provide the base for the fabled tower. I’ll remove the wooden frame, and backfill some dirt next weekend.

Yesterday they dug the hole, today they filled it in.

The tower base frame was set solidly in the hole – affixed with 2 metre star-posts welded in each side. and rebar affixed below. The concrete was poured expertly into the centre of the frame – it didn’t flinch. I don’t know (yet) how much concrete was used – I left for work immediately after taking this photograph. Again, it was dark when I returned home, so I’ll have to wait until tomorrow to see the finished product.

… then wait at least 3 or 4 weeks for the concrete to “cure” before the tower gets erected. It takes that long with winter temperatures here for the concrete to set.

… the tower base laying has begun! The most time-consuming part (that I was involved with) was determining the line running from true east to west. We were using a briefcase as a flat surface upon which to lay the compass and discovered that the briefcase had more metal that we imagined only after we put two compasses side by side and discovered them pointing in different directions.

It was a typical, glorious winter’s day. At the time this photograph was taken it was about 6 degrees C (43 deg F). Note the typical builder’s pose – one working, two supervising

I left the diggers at it and went to work. It was dark when I returned home tonight so I haven’t been able to see in any detail the result of the day’s work. As best I can determine, they’ve almost got the the stage where the concrete can be poured.

When standing next to the hole, it looks huge – like a swimming pool.

The rain having stopped, with over 44 mm ( 1 and 3/4 inches) in the past two days, we’ll have another attempt at laying this fabled tower base tomorrow morning. The ground’s pretty wet but I doubt that it’s soaked in far enough to make the clay soil too unworkable.

The digger should turn up some time after 7:30 am. Surely it won’t take too long to dig the actual hole, but it could take a while to get the boxing done just right … and to get the alignment just so. The idea is that the tower will be installed with each of its four sides aligned with true north, east, south and west. The rotator, when switched off, will sit looking true south which, fortuitously, means that my VHF/UHF beams will be sitting covering the arc between Sydney, Tasmania, and Melbourne – where much activity resides.

Well I spoke too soon yesterday. After 25 mm (an inch) of rain overnight the project was postponed for a couple of days (we’re in the midst of drought here so any rain is extremely welcome).

I don’t think that the bobcat would have had too much of a problem digging the hole but the builder would have had a squishy time in the clay with the boxing (to fix the tower base into the concrete).

Trivia of the day: In preparation for orienting the tower I determined that True North is 11.629 degrees west of Magnetic North at this location.

At long last, after a much-longer-than-really-seems-possible delay, the hole will be dug, and the concrete for the base of my 25 metre (82 foot) self-supporting tower will be laid tomorrow. All being well, the earth-moving equipment will arrive to dig the hole at around 8 am.

The tower itself comprises nine 2.5 metre sections, with a 2.5 metre mast sitting atop the rotator platform.

Off the top of my head, I think the 3m x 3m x 1m hole will be filled with 13 tonnes (14.3 tons) of concrete. I’ll confirm this after the event. Given that the tower is self-supporting, there are no guys to keep if upright, the “ballast” at the bottom has to do all the work.