Excavated dodecahedron – complete

Finally managed to finish the excavated dodecahedron!

First I made another six pentagonal units.

excavated dodecahedron work in progress

Then I stitched them together to form the second half.

excavated dodecahedron work in progress

Then I joined the two halves to form the complete dodecahedron.

complete excavated dodecahedron excavated dodecahedron

It is a little wonky – it was tricky to get all the pentagonal units exactly the same size. And some of the joining could have been neater, though it was tricky making the final joins, as I had no access to the needle on the back side.

But I’m pretty pleased with it as a proof of concept. 🙂

Excavated dodecahedron – work in progress

I started thinking about other ways I could use the coiling and joining technique I used for my tortoise, and it occurred to me that the tortoise shell was essentially half an irregular stellated polyhedron.

A polyhedron is a 3D shape with flat faces, eg a pyramid. In a stellated polyhedron, the faces, rather than being flat, are extended to form new polyhedra – like a pointy star.

So I thought I would try to make a dodecahedron (12 faces – each face is a regular pentagon). The individual elements making up the tortoise shell were a mixture of hexagons and pentagons, so I already knew how to do this shape.

But instead of making a stellated dodecahedron, where the faces point outwards, I thought I would try a concave or excavated dodecahdron, where the faces dip inwards.

Whether it’s stellated or excavated, the individual units are made in exactly the same way – it’s just that the inside is the “right” side for an excavated dodecahedron, while the outside is the right side for a stellated dodecahedron.

I used the same yarn and pattern as for the tortoise shell, as I had quite a lot of yarn! But I had a brief moment of panic when I discovered that the retailer who supplied the copper wire I used for the core was no longer stocking it! However, I round an online supplier, so all was well.

The first sample units I made were quite deep, with steeply sloping sides. But when I joined two together, I concluded that they were probably too deep. To create a dodecahedron, the units have to fold back against each other , and if they are too deep they may not be able to do this.

dodecahedron sample

So I made the units shallower.

excavated dodecahedron 6 units

Then I joined five units together around a central unit.

excavated dodecahedron 6 units joined

Then I joined the sides to create half a dodecahedron.

half an excavated dodecahedron

Now I just need to make the other half and join them together!