Untitled, six species of wood. Contributed by Glen Whitney.
[80 F, 150 E, 72 V] The “propello” operation devised by George Hart forms a new polyhedron from a previously known one in a way similar to the snub operation that produces the snub cube, but it introduces quadrilaterals rather than triangles between the expanded faces of the original polyhedron. This precisely machined wooden sculpture illustrates the propello operation applied to the regular icosahedron. Invisibly embedded in a natural cavity inside this model is a rhombic triacontahedron, which in turn has a perfectly cubical interior chamber.