Issa and I are building a 32′ diameter, 16′ tall geodesic dome. We’re using the instructions on desertdomes.com. This weekend, we made a big chunk of progress, so it’s as good a time as any to post an update.

Above, you can see some of the poles that have already been cut and marked. We’re using colored duck tape instead of paint, because a friend told us that paint just flaked off and wasn’t a good choice. The pre-torn pieces of yellow tape are stuck to the edge of the table saw.

Here are some more cut poles. The dome we’re building, a 4v frequency, has six different lengths of pole. Other designs have fewer pole lengths, which simplifies construction and building, but the trade-off is that it requires longer poles to get the same size dome. By building a 4v dome, we keep our longest poles down to about 5′, a manageable length. If we were to build a 2V dome of the same size, there would only be two pole lengths, but they would be about 8′ and 9′ long. The shorter strut lengths also mean that each individual strut can be made from thinner tubing, since it’s shorter and less likely to bend. We’re using 3/4″ tubing, which is expected to provide enough strength to climb on the dome and hang from it, as long as you only put weight on the vertices where the struts come together, and not on the middle of the struts.

A 4v dome has a total of 250 struts. That’s a lot of cutting! Precision and repeatability is important, but so is efficiency, because there’s a lot of work. The picture above shows the jig we built for cutting the poles to length.

A stop-block is clamped to the jig such that the poles are cut to the right length when pressed against the stop-block. After each cut, the pole was compared to a reference pole that was known to be the correct length. This gave us an opportunity to catch mistakes without having to pull out a tape measure each time.

This board is our master cut-list. It’s screwed to the barn so it doesn’t get misplaced. The right-hand numbers are the center-to-center distance between the bolt-holes that will be drilled in the end of the poles. This is the most important measurement to get right, because it determines whether the dome comes together or not, and whether the dome looks like a dome or a squiggly mess. The left-hand numbers are the lengths of pole to actually cut. The poles are 1.5″ longer than the center-to-center distance, to allow extra metal at the end. You can’t put a hole into nothing, you know!

Here, you can see a cut being made on the chop-saw. We picked it up for about $50 used, and the money was well spent. It cut through the EMT in about 5-8 seconds and the cuts were pretty consistent. Anyway, we got the poles all cut.

The next step is to flatten the ends of the poles and drill bolt-holes in them. For the flattening, there are many methods, including good old sledgehammers and vices, but for 250 poles (or 500 ends that need flattening) this works out to a hell of a lot of manual labor. Instead, Age brought over a hydraulic press. The only thing better than a hydraulic press would have been a hydraulic press hooked up to an air compressor, because as-is we had to jack the hell out of that thing. But still, it was worlds better than the more-manual alternatives.

Here, you can see Age lining up the plates while I get ready to jack down the piston and squish the end of the pole.

This is a squished pole-end. It’s very important that the two ends of the pole end up flat in the same plane. As you can see here, I cut a V-groove out of a 2×4 to a width and depth that would allow the squished end to lay flat. This mean that the other end, when squished, was in the same alignment as the first end.

Now for the drilling. Above, you can see us setting up the jig that would allow us to drill the first hole in the pole, exactly 3/4″ in from the end of the pole. The tape is marking the line where the hole should be, and the pole is set on a piece of wood with a V-groove cut in it to align the tubing.

Issa drills one of the first holes.

Here, she has drilled more than a few!

Looks good to me!

What a mess! In order to prolong the life of the drill bit, we brushed it lightly with motor oil before each hole, hence the oily wood.

Issa checks the first six poles that we drilled to make sure they would fit correctly on the bolts we plan to use. If we need to make the holes bigger or get longer bolts, now is the time to find out!

By the end of the day today, we had flattened the ends of all of the poles and drilled holes in one end of every pole. Tomorrow will be one of the most critical parts of the build. The center-to-center distance of the holes in the struts must be exact, so drilling the second hole is where the dome will be made or broken. We’ll be fine, and we’ll take pictures!