Felix Candela

The Norton lecturer for any given year could be a man from any of a veritable potpourri of fields which the University considers to belong among music, the arts, or literature. This winter's speaker is architect Felix Candela, who entered the profession on the theory that it "sounded as good as any other" and is now one of the most skillful designers of thin-slab concrete structures in the hemisphere.

Mr. Candela's genius has not been solely in what amounts to the "sculpture" of aesthetically pleasing structures, however; the architectural concept he has developed over the past ten years now makes possible the construction of these buildings at costs in many cases lower than those of more conventional projects.

Thin sheets of saddle-shaped concrete typify Mr. Candela's architecture; a geometrician would describe them as sections of a hyperbolic paraboloid. Their most common application is in roofs for large buildings, since an inch-and-a half thick slab shaped in this way requires only one support for every 2500 square feet, far fewer than a flat surface would require.

"Curved surfaces," Mr. Candela explains, "no matter what type, are always stronger. This is one reason why snail shells are curled, or why it is safer to design automobiles with curved pieces of steel."

But there are many different curved surfaces which an architect might wish to use in a building, and no single quality of the hyperbolic paraboloid is unique. One might naturally wonder why this surface should be any better than some other of a slightly different but equally pleasing shape.

The answer lies in the fact that only a very few of the many abstract curves available can be analyzed with sufficient mathematical ease to permit an architect to calculate stress factors at a given point. And no curve satisfying the mathematical requirements lends itself so simply to the straight line geometry of the carpenter who must build a mold out of flat pieces of wood to form curved concrete surfaces.

"This is a very useful property, to say the least," Mr. Candela points out. "Suppose you tried something like a dome-the mathematics is simple enough, but to build the form you must twist the wood in a very difficult manner. Domes are difficult, and very expensive. I have only ever done three or four of them."

The great advantage of the hyperbolic paraboloid is that, because of a rather devious characteristic of the surface, a carpenter building the form does not have to bend his wood. "I am not a mathematician," Mr. Candela asserts, "and this is difficult to explain." Perhaps the easiest way to understand the principle is to remember that at any point on a saddle a straight line may be drawn which does not leave the surface, as it would, for example, with a sphere. And where the geometrician can draw straight lines, the carpenter can nail planks.

"I first became interested in the hyperbolic paraboloid about ten years ago," Mr. Candela says. "Before then, some French engineers had experimented with the surface briefly (during the 1930's) and even built a few structures using it. But they failed to realize either the artistic possibilities, or the economic ones."

The mention of the economic aspects of hyperbolic paraboloid design is characteristic of Mr. Candela, an essentially pragmatic man. He rarely mentions one of his work's objects-aesthetic appeal, without bringing up the other-practicality. One cannot talk with Mr. Candela for more than about ten minutes without sensing the balance between these goals: 'We can build out of shell concrete cheaper than any other material in Mexico," he will say. And two minutes later, while drawing complex curves and surfaces on the back of an envelope, "I like that one."