3.4 Spiral Dissection. The object of Figure 10 is in fact one part of a dissection of a cylinder into two parts. This structure could also be recognized in the tetrahelix of Figure 5. And also Leonardo da Vinci made use of it in his drawing for the double spiral staircase (Figure 11) [3].

In these examples the spiral cut is applied to cylindrical shapes. The parts are still close to the normal spiral shape. When we apply the spiral cut to a cube the shape of parts becomes more interesting. So we can divide a cube into two equal spiral shapes that can be twisted in and out each other (Fig. 12). And even a spiral dissection of a sphere can be made (Fig 13.).
Figure 12: Spiral Dissection of a Cube.
Figure 13: Spiral Dissection of a Sphere.