The sailing trials are not till June, but the America's Cup defender may already have been prefected in water tanks at Hydronautics, Inc., near Columbia, Md.

The most extensive model testing program ever for a sailing yacht was conducted as the new 12-meter Enterprise was designed. Now, with Enterprise christened at Minneford's Yacht Yard in New york, where she was built, and trucked to San Diego for winter wailing, her designers, backers and crew hope for a turn of speed that will indicate the elaborate program contributed to the design of the fastest 12-meter ever built.

The testing began a year ago when Enterprise designers Sparkman and Stephens and the owners, the Maritime College at Fort Schuyler Foundation, tested a 22-foot, one-third scale model of 1974 America's Cup winner Courageous at Hydronautics. The tests established a starting point and a comparison for any design changes.

Next came tests of a series of 8 1/2 foot, one-eighth scale models in the towing tank at Stevens Tech in New Jersey. After testing 20 designs the hull form for the Enterprise had been so closely determined that construction actually began two weeks before the final series of tests were run on a final 22-foot, one-third scale model of the new design at Hydronautics in September.

It was, as designer Olin Stephens observed at the time, testing after the fact - with the boat already about half lofted and work on the deck and frames begun. But it was not too late to change the design if the tests did not show improvement over the Courageous model.

Dave Pedrick, Enterprises project manager, said, "If something suddenly indicated the boat was a loser, we could scratch everything and go from there . . ."

The final tests were double-checks of the design and were to determine which of two trim tabs and two proposed rudders were best.

No large-model testing has been done in previous America's Cup campaigns, although all 12 meters designed for the cup trials since 1958 have been evaluated as small models. The new interest in large models was sparked by problems encountered in analyzing data from small-model testing - problems that showed up most dramatically in the unusual and unsuccessful stern configuration of the 12 meter Mariner in 1974.

Naval architects long have recognized that errors called "scale effects" appear in correlating performances of small models and full-sized yachts.

Karl L. Kirkman, head of the experimental projects at Hydronautics, and Pedrick, chief of the scientific section at Sparkman and Stepehns as well as project manager for both Courageous and Enterprise, studied scale effects at length and presented their findings to the annual meeting of the Society of Naval Architects and Marine Engineers in 1974.

They concluded that increasing model size was the most promising method of improving predictions. Their data offered guidelines toward selecting model sizes that would give reliable results inexpensively.

When Sparkman and Stephens decided to use the large models in Enterprise's test program, Hydronautics' tank, the largest nongovernment facility of its type in the nation, was the choice. The tank is 420 feet long, 13 feet deep and 25 feet wide, with sides designed to dampen the waves created as the model moves down it. More than big enough to test the 2,500-pound model.

Knowing what numbers he was looking for on the instruments hooked up to the model, Pedrick was able to say cautiously after the first few runs, "a quick check of the data shows this is a small improvement over Courageous." But tests continued almost around the clock for two days before the designers and tank personnel were satisfied with the results and the program was complete.

Construction at Minneford's proceeded rapidly. It had taken six months to build Courageous, but because of greater experience in working with aluminum and improvement in production organization, Enterprise was built in half that time.

A crowd of about 500 people gathered for a christening party at Minneford's Dec. 4.

Enterprise skipper Lowell North, Olympic gold medalist in Star class boats and president of North Sails, which is outfitting Enterprise, introduced crew members: Marlin Burnham, upwind helmsman; Richard du Moulin, navigator; John Marshall, sail trimmer, and Emry's Black, James Caldwell, Andrew MacGowan, Robert Norman and Stephen Taft, all members of Intrepid's crew in the 1974 America's Cup campaign; plus Rod Davis and Roger LeBlanc.

The ceremony concluded with Mrs. George F. Jewett Jr. smashing a beriboned bottle of champagne over Enterprise's bow and the Maritime College band playing "California Here I come," sending Enterprise on her journey to San Diego for shakedown.

In the trials she'll meet the other new U.S. 12 meter, Independence, which is designed, fitted with sails and skippered by sailmaker Ted Hood. Courageous, winner of the Cup in 1974, may compete, and perhaps some other reconditioned 12s will join the series of races off Newport, R.I., during June, July and August to choose the America's Cup defender.

In September the defender will compete in a four-out-of-seven series for the America's Cup against the winner of an August elimination series sailed among challenging yacht clubs from France, England, Sweden and Australia.

The America's Cup is the oldest international sporting trophy still awarded in competition. The cup itselt, sometimes known as "the Auld Mug," five-time challenger Sir Thomas Lipton's name for it orginally was called the 100 Guinea Cup because that was its monetary value in 1851 when it was won by the schooner America competing against a fleet of 14 foreign vessels in a race around the Isle of Wight.

The America's Cup was deeded to the New York Club in 1857 for international racing. The first competition was in 1870 and through 1881 a challenger had to race against a fleet of defenders. In 1885 the first match race series for only two boats was held.

In the 107 years of the America's Cup competition, since the schooner Magic bested the English schooner Cambria, no foreign yacht has ever won the America's Cup.