Veggie Waffles: Test 1

Initially I was a bit nervous to dive right in a cast an entire 2'x3' panel without mocking up how to create the hollow cells, make holes to allow for irrigation and mounting hardware to integrate. I also wanted to test the reinforcement cage idea I had, would small spans of metal grid tied together with wire be strong enough.
So I built a single cell, about 14" x 14." The formwork was relatively straightforward to build and I opted to create the waffle cell by attaching pieces of wood perpendicularly to one another, so it was really just edges rather than a sculpted mass.
The concrete mixture I used was 2 parts light sand, 1 part coarse/dark sand, 1 part cement and water "to taste." It was a pretty solid mixture...and as I would see later did not make the best waffle.

after it cured for a bit and right before I removed it.

Here are the reasons I think the center didn't come out.
1. There was no taper to the cell. This would have helped immensely
2. I screwed the wood pieces from the side that would later be covered with concrete, it's likely that had I attached them from the inside somehow I could have gotten all but the bottom one out.
3. I used vegetable oil instead of spray release...it's worked well for me in the past, but this form was about 2" deeper than any other casting I've done.
4. The wood dowels I inserted all the way through the formwork essentially trapped those pieces of plywood in the middle.

Lessons Learned:
1. Taper anything that is getting "buried" in the concrete and will later have to be removed.
2. It's probably easier to drill holes after the fact than figure out a way to cast them.
3. Primer and spray release will probably make things easier.
4. Make screw heads accessible during deconstruction.
5. A solid mass probably works better than a shape created of pieces for the cell void.

With this in mind I started working on the formwork for my full-scale panel.
Oh, and I also mocked up a little gabion pocket. Fun with the sheet-metal bender!