But gold was never his goal, Head insists. All along, from the late-night flash in early 1974 to the development of the first Prince prototype later that year, Head says that he had only two things in mind: "To make a racket that felt good, and one that I could play better with." The Prince passed the esthetic rightness test convincingly. As administered by Head to any doubters he encounters, it goes like this. Close your eyes. Swing two rackets successively, one a Prince, the other a conventional racket. Now try to guess which is which. "No one can do it with consistency," Head says proudly.
The hitting exam went equally well. "I could play much better immediately," says Head. "The feeling of stability was much more than I expected." Friends who in the past were never overly eager to rally with Old Scatterball began inviting him to play. Tallying up the test scores, Head came to a logical conclusion: "As soon as I found out that the racket helped me, I thought I might as well try it on the market."
Head called a meeting of the Prince board in 1975. "As chairman, I was wearing two hats in this instance," he says. "So I went to the meeting in my chairman's hat and said, 'Gentlemen, there's a man here to show you a new product!' Then I put on my inventor's hat and made my pitch." Mal Bash, now Prince's vice-president in charge of engineering, recalls, "If another inventor had come in with a crazy-looking racket like that, we would've turned him away. Howard sure knows how to sell an idea."
The U.S. Patent and Trademark Office wasn't buying, however. "When I first applied for the patent," Head says, "the inspectors—who act as both judge and jury—refused the application, claiming that my idea was no more than an obvious extension of the state of the art in tennis-racket design." Turned down twice more, Head became three times more determined to amass the kind of not-so-obvious scientific evidence that would dazzle the patent boys.
Working in a lab with Kenneth Wright, a consulting engineer, Head set up a sort of shooting gallery with a Prince racket, clamped in a vise, squaring off against a Prince ball machine at 10 paces. High-speed cameras set for 400 frames a second were stationed next to the racket to record the coefficient of restitution, which is the relationship between the incoming speed of the ball and the outgoing speed. The maximum coefficient for a stationary standard racket was found to be .57; that is, the outgoing ball retained 57% of its incoming velocity. To achieve this maximum return, the ball had to strike the racket's center of percussion, the magical "sweet spot."
So much for the ground rules. In practice, the sweet spot is neither unique to tennis nor inconsequential to success. It even sings sweetly: "ping" to the tennis player, "click" to the golfer, "crack" to the baseball player. The sounds signal the soul-satisfying moment when the entire swung weight of the instrument is laid squarely on the ball, when the swing is free of vibration, when the racket, club or bat becomes an extension of self. "When Reggie Jackson hits the ball and feels nothing in his hands," says Head, "he knows that ball is gone." Such moments are rare because the sweet spot is by definition small and elusive. But what if it were bigger, more responsive, easier to find?
Once the barrage began in Head's shooting gallery he had some doubts about the Prince's performance under fire. Shots aimed directly at the center of the strings showed coefficients in the low .50s, respectable but below the .57 high of the standard racket. But as the shots were aimed lower the coefficients began to go up—.55, .58, .62, .67! Could it be that the center of percussion, the evasive sweet spot, was not in the center of the strings as had always been assumed?
Yes, says Head. "We were startled to discover that the best place to hit the ball was in that three-inch area of added length, an area that doesn't even exist on conventional rackets. It's about two-thirds of the way up from where you grip the racket—the throat of the standard racket." Moreover, the tests showed that not only did the "super sweet spot," the area closest to the throat of the Prince, deliver 20% more power than the centers of percussion of other rackets, but the entire sweet spot was also four times larger than the average, the difference between an open hand and a fist. Serendipitously speaking, Head says, "I lucked into it."
Head then hit the Patent and Trademark Office in its center of percussion. "When I demonstrated the development of the sweet spot to them in engineering terms," says Head, "they had to concede that it was a totally unexpected outcome resulting in an invention." He was granted Patent No. 3,999,756 in 1976. It's good for 17 years.
Ever since, as chairman, principal stockholder and chief tinkerer, Head has been intimately involved in new racket design and other developments, such as a unique graduated stringing pattern that spaces Prince strings closer at the center, wider toward the edge, for more uniform response. But of late he is content to leave the daily operation of Prince's new $1.5 million plant and 100 employees in the hands of John Murray, his enterprising president, who says, "I think Prince is going to take over the racket business."