In the mid-1960s, a shipping magnate named Jakob Isbrandtsen told the illustrious yacht designers, Sparkman & Stephens, to design a sailboat that could compete with the best. Something special emerged from the blueprints in 1969. Built by Huisman, the Dutch firm, it had a sleek aluminum hull, a sparse interior by contemporary standards and a flush, utilitarian deck. Isbrandtsen called it Running Tide. Since his commercial ships were all painted green, the same color went onto his new racing sloop. Tide won the 1971 Southern Ocean Racing Conference (SORC, pronounced Sore- see) in Florida, the equivalent of the American yacht-racing Olympics. It won its class in the Bermuda race the same year. Then Isbrandtsen put her up for hire. Ted Turner, ocean racer and cable television entrepreneur, leased and raced her for six months. One of his opponents that year in the Annapolis Yacht Club Fall Series (races held in the Chesapeake Bay) was a wealthy Alexandria developer named Al Van Metre, sailing a 50- foot aluminum sloop of his own. "Tide was fast as hell," Van Metre says. "We considered ourselves fast, and she cleaned our clock."

Van Metre decided to buy Tide; so did Turner. "We had quite a fight," says Van Metre, an understated appraisal of a serious bidding match. He won, the beginning of a rivalry that enlivened racing for a decade. Turner bought a similar sloop, Tenacious, a converted Americas Cup 12-meter boat. He and Van Metre pitted their S&Ss in the Atlantic and the Caribbean, the irreverent, cigar- wielding cable television magnate battling the shy, nonsmoking builder of apartments and shopping malls, each in fashionable aluminum hulls equipped with the latest in sailing technology and nurtured by seemingly inexhaustible bank accounts--two prerequisites in serious ocean campaigning.

"Tide was a dog downwind," Van Metre said often, meaning that she performed poorly when the wind was behind her. He and his son, Al Jr.-- known as Beau--put on longer spinnaker poles, which helped. They had her rewinched. "We were always fooling around with the deck layout." They added nine feet to the mast, but that unbalanced the boat and they had to chop it off again. They added a new, three-spreader rig.

Tide became a top contender in that endless circuit of ocean races that can keep a skipper and crew occupied year round. In 1976 she took the Bermuda trophy after a stormy crossing of the Gulf Stream, and a heady shellacking of Tenacious. Three years later, in the Annapolis-Newport race, Running Tide and Tenacious dueled to the mouth of the Chesapeake, tacking side by side, the crews exchanging barbed pleasantries. Tenacious went out to sea, following the rhumb line in light air toward the tip of Long Island; Tide ran up the coast, reaching for thermals that never developed. Turner arrived in Newport hours ahead of Tide. Van Metre, gracious in defeat, bought dinner for the entire Tenacious crew, but Turner didn't stay around long enough to eat it.

They still talk about those days aboard Tide. It was all so much fun, before Turner lost interest and sold his boat. Van Metre should have sold his, too, according to conventional wisdom. Boat design was changing fast, with leaner, lighter, faster hulls that made Tide's swept-back keel look a downright dowdy. Serious--and, of course, rich--ocean racers buy new boats every year, just to keep up; Van Metre's yacht was already 10 years old.

But as his investment in Running Tide had grown, so had his affection. "He'll never sell her," says his wife, Joan. "When he dies, he'll want to be put on deck and Tide sent out to sea, like a Viking ship."

Last year, instead of racing in the SORC, Running Tide was delivered to Pilot's Point Marinain Westbrook, Conn., for extensive modifications, a decision that caused speculation in boating circles. Were the Van Metres wasting money on geriatric maintenance? Had Van Metre, a meticulous sailor and dispassionate businessman, succumbed to the old salt's sentimentality, holding onto a boat that could no longer serve him?

Tide's keel was made steeper in front for upwind efficiency--more like the squared-off tip of an airplane wing than the shark's fin it had been--and slimmer for downwind speed. The built-in bunks were torn out, replaced by more, lighter pipe berths --canvas-covered bunks strung on pulleys where crew sleep like stacked cordwood. A new 12-volt electrical system, navigational station and an $8,000 instrumentation system, including a Brookes and Gatehouse Hercules 190 computer, were installed. The Westerbeke diesel engine was overhauled. The cockpit was enlarged, and a bigger wheel installed, to let the helmsman sit further to weather and keep the sails in view. The exterior and interior were painted, and a new rudder attached. The cost: $153,000.

Tide's interior had become Spartan, but much roomier. And overall Tide had lost 4,000 pounds, a serious factor in the equation of balance and responsiveness. She was known to be faster off the mark, but "tender," heeling more easily, which could mean a poorer upwind performance.

"We won't know if the modifications work until we race her," Van Metre said this spring, a few days after Tide returned to Annapolis. The test would be the 1983 Annapolis-Newport race. In the dozen years that Tide had been berthed in Annapolis, she had become the preeminent local race boat, with an illustrious history of wins and near- wins, always well-kept, a credit to the port, a defender of its honors. But Tide had never been first across the line in Newport.

Her chief contender was a local 61-foot yacht named Cayenne, resplendently white, with a taunting red, orange and yellow stripe stem to stern. Cayenne was fast--faster than Tide, according to some--and six years younger. She belonged to Don Tate, an industrialist and able sailor who wore a beard trimmed to his jawline. He bought the boat from the Navy, which had received it as a donation from its first owner. Cayenne had also been called Gusto, and Guerriere, a seasoned campaigner and a wicked reacher in good air.

Several of Tide's crew had sailed first on Cayenne. Tate used the Swedish watch system--four hours on and four hours off during the day, and six- hour watches at night. He allowed beer-drinking during the race, and an occasional cocktail before dinner. Van Metre allowed no drinking whatever. His watches--three hours on and three off--ran around the clock.

The two owners maintained a friendly if casual association. But the two crews referred to one anothers' boats in disparaging, often scatological terms, all part of the adrenaline pump before any big race. The paid deckhands--three each on Tide and Cayenne--bet 18 cases of Heineken's beer on the outcome of the Annapolis-Newport contest. Cayenne had replaced Tenacious as the boat for Tide to beat.

Two days before the race, the decks of both boats were littered with tools, wires, sail bags, rope and caulking guns. The man responsible for Tide's readiness, John Patterson, 28, had first sailed on Tide when he was 15. He became part of what Van Metre called the "Kiddy Corps"-- eager young sailors willing to scrub the bilge or climb the mast just for a chance to go out. Patterson had grown up on the boat. Now he was captain. Van Metre believed in the concept of executive vice presidents, and Patterson was his executive vice president in charge of maintenance and seaworthiness.

Patterson's wife, Marcie, was pregnant and expected the birth of their second child sometime during the race. "If the baby's born while we're at sea," Van Metre said, "I'll relax my regular rule and we'll all have a glass of champagne." Meanwhile, Patterson was having shackles welded, and attending to the provisions required by the Race Committee. An inspection team with a clipboard could visit Tide at any time.

The committee had chosenboating circ Cayenne as the "scratch" boat, meaning she had the highest rating and the best chance of being first across the line in Newport. The race was due to start at noon on Saturday, and late Friday afternoon the skippers gathered in the auditorium of the Naval Academy for a briefing about rules and the weather. Van Metre, wearing his habitual yellow sweater, chinos and New Balance tennis shoes, sat and listened to the bad news: a high-pressure system was anchored over the eastern United States, which meant light and variable winds--and maybe no wind at all. Tide had traditionally performed best in a heavy seaway; light air favored smaller, lighter, newer boats.

Van Metre skipped the cocktail party after the briefing, and returned to dockside. He wanted to see the new headsail from North Sails, expected for delivery at any moment. The crew was busy onloading food for the race.

He boarded his 71-foot motor yacht, Silver Seas, moored next to Tide. It has three staterooms and a captain's quarters, and is taken every winter to Fort Lauderdale, where thMetres use it as a second home. Van Metre poured some Gallo Mountain Chablis over ice, and sat down at a broadn the salon. He said the weather forcast disappointed him, and that he worried about the overall performance of the new Running Tide: "I'd feel a lot better if ould test that new sail."

He sipped the wine, gazing at the drawbridge through which the boat would pass in a few hours, on its way to NeIf we can't get Tide sorted out by the SORC," he said, "we'll grind her up and make beer cans." CAPTION: Pictures 1, Beau Van Metre, 36, is an instinctive sailor who isn't interested in high-tech sailing. Picture 2, The 61-foot, 5,200 pound aluminum sloop Running Tide tacks down the Chesapeake Bay at the start of the Annapolis-to-Newport race. The sail on the left is the new Mylar genoa, a stitched headsail that cost $8,000. Picture 3, The tailor and crew members work together to keep the sails tight against the wind. When the tailor calls, "trim," sails are cranked in, and speed is maintained.