So how does one go about getting a 4' cube of concrete? Well, you start by building a “form” – essentially a mold. That's what's in the photo at right, shown in the same orientation that it will be used in. I built that behemoth today, starting with a run to Lowe's to get the materials. The top and bottom of this form are open. The bottom will sit on the base of a big hole I'm going to dig tomorrow; the top is open so that the concrete truck can easily fill the form. It all went together rather easily. The design is about as simple as can be, and the tolerances aren't tight :)
That form isn't quite finished yet – I still have to add some wires and eye bolts to hold the steel sleeve (that actually holds the flagpole) in place while the concrete is poured. The top of the sleeve will be in the exact center of the form, and will extend about 3/4" higher than the edges of the form. When the concrete is poured, I'll be finishing it with a slight slope from the center to the outside, so that water will run off it easily. The top of the form (and the edge of the concrete) will be at the same level as my yard, so I can mow around it easily.
The form will hold about 62 cubic feet (or 2.3 cubic yards) of concrete, after accounting for the space occupied by the hollow sleeve. I'll be digging a hole that is substantially larger than that: about 6' x 6' x 4' - which means I'll be excavating about 5.3 cubic yards. If you're familiar with bulk materials, you'll know that that's a rather large pile of dirt! I'm very glad I'll have the backhoe to do this with. If I had to do it by hand, I'm not entirely sure I'd survive the project :)
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