I really owe my Uncle Mike for inspiring my interest in arches. He came up with a way to carve an arch out of sand on the beach. After doing that with him, I was hooked.
A week later I had designed on paper a self supporting arch made out of 5 discrete pieces of wood. It was when it showed up in the mail that surprised me!
Interestingly enough, the shape of a self supporting arch is the same shape that a cable hanging between two points makes--the catenary. Obviously the arch is inverted to the catenary, but other than that, they are the same shape.
A catenary is not a parabola, although on first glance it may appear to be so. The derivation for the catenary is, quite honestly, beyond something I could do. See here if you are interested, but otherwise suffice to say that the catenary is a hyperbolic cosine.
© 2006 Nic Reveles