Texas dentist Leo Windecker did not set out to make an invisible aircraft. All he wanted, 30 years ago, was to use his knowledge of anatomy to create a substance that would strengthen the small planes he piloted on weekends. The blend of gooey plastics and fiberglass that Windecker produced in his Houston garage was, as he hoped, light and even tougher than human bone, until then, in strength-to-weight ratio, the sturdiest material known to man. Windecker's mixture had another serendipitous quality. It absorbed microwaves and distorted radar signals.

Now this backyard invention has been refined and is being used in the development of the much-publicized Stealth bomber, which by the late 1980s is supposed to be able to fly safely through enemy radar. When the "invisible" aircraft project was publicly announced by the Secretary of Defense, Harold Brown, in August, Windecker was aghast. "It was a damn shame to let it out," he says. "Now our enemies can take countermeasures."

Windecker was so sure of the importance of his composite that he quit dentistry in 1959 and signed on as a consulting engineer with Dow Chemical in Midland, Texas. In 1962 he went to Washington to alert the Pentagon. "I was sent from place to place," the inventor, now 59, recalls. "Nobody seemed to be able to do anything."

In 1967, after building a prototype aircraft with Dow, Windecker left the company to develop his own line of light planes, selling Dow most of his patents and rights. When his company began to run out of money in 1970, Windecker returned to Washington with his idea.

This time the Pentagon listened, tested Windecker's plane successfully and awarded his firm a $400,000 contract to build a military version. It was delivered in 1973. That was the inventor's last personal contact with the Defense Department. Today the Pentagon refuses comment on the plane, which is reportedly under construction with variations in size and shape at Lockheed in Burbank, Calif. Before it was designated Stealth, Lockheed workers called the craft Harvey, after the invisible rabbit in Mary Chase's play.

A Karnes City, Texas native who built telescopes and model planes as a boy, Windecker graduated from the University of Texas Dental School in 1948. He now lives in Midland with his wife, Fairfax, also an ex-dentist, and is helping International Harvester develop fuel-conserving vehicles that use his composite. "It would be nice," Windecker says wistfully, "to have a dollar for every car and truck made of the substance in the future." And, he might add, 50 cents for every police radar they avoid.