The first idea was to create a base from shaped, slotted sheets of cardboard supporting some sort of curved seat. 

However, it was easy to imagine that the support structure would distort when loaded on account of the fact that there was no triangulation

I looked at a radial arrangement but it was immediately clear that the connection at the centre would be difficult. 

This was the key point in the evolution of the design – a five-pointed star would have a triangulated structure and an even distribution of strength