AMERICA’S CUP : Challengers Set to Launch Bids for Sailing’s Top Prize : 13 Yachts Start the Series of Races Sunday

It’s only three feet tall and worth maybe $750 if it were melted down, which some observers think would be a good idea, since it isn’t the best-looking trophy in the world.

But there, with its gaudy Victorian scrolls and flourishes, a relic from days when ships were powered only by the wind, sits 134 silver ounces of sailing’s most prized possession, the America’s Cup.

Starting Sunday--it will be 10 p.m. PDT Saturday--in the Indian Ocean off the coast of Perth, Western Australia, 13 yachts from six challenging countries will launch their bids to remove the cup from Down Under, where it has resided in proud, public splendor since the Aussies removed it from the New York Yacht Club in 1983.

Lots will be drawn today for the first round of match racing around the 24.1-mile triangular course a few miles north of the port suburb of Fremantle. The four Australian syndicates competing to defend the cup will start their races Oct. 18.

By the time the ultimate defender and challenger meet in a best-of-seven series four months hence, they all will have spent about $200 million in pursuit of a glorified spittoon.

For each group, there will be three rounds of racing, followed by semifinals among the top four boats the week after Christmas, challenge finals late in January and the championship series starting Jan. 31. Each win in the first round is worth one point, escalating to five in the second round and 12 in the third.

If there is a sentimental favorite among the challenging 12-meter yachts, it is Dennis Conner, who lost the cup to Alan Bond’s Australia II syndicate in ’83 after defending it successfully in ’80. But Conner is hardly a sentimental figure. He is a hard-driving and hard-driven competitor who would do almost anything to win, especially now.

L.J. Edgcomb, a cup veteran now an executive with the rival Eagle syndicate from the Newport Harbor Yacht Club, says: “Dennis Conner has always been a disciple of being the best prepared. Now he’s going to have some people out there who are equally prepared.”

Most will be sailing a new breed of 12-meter--some are evolutionary and some are revolutionary--born of computers and space-age technology. The most radical is U.S.A. from the St. Francis Yacht Club’s Golden Gate Challenge which has its rudder in the bow--even a more bold departure from conventional design than the winged keel used by Aussie II in ’83.

Said Jeff Spranger, a veteran cup journalist: “If it doesn’t work, they have no fall-back position.”

But if it does work, as did the winged keel, everybody else will have a rudder up front in 1991.

The boats also have been built stronger than before to survive the heavy southwest Australian summer winds, called the Fremantle Doctor, that stir the seas into a super-wash cycle and bring cooling relief to Australia’s arid west coast.

But it’s only early spring Down Under, and the doctor isn’t due for a while, leaving the competitors to guesstimate the milder conditions they’ll face in the early racing. Most have been gearing their boats down for lighter wind, leaving the wealthier syndicates that have more than one boat a problem.

“That’s one of our strengths,” said Edgcomb of the lone Eagle effort. “We’ve got other people out there who don’t know if Boat A or Boat B is best. They’re going to have to use October as a testing platform.”

Perhaps. Boats may be modified and remeasured after each round, and a syndicate can even switch boats after the first round, but it would have to forfeit any points won if it did so.

And to use the first round for testing just because the points don’t mean much could mean economic disaster for the poorer outfits.

“The only way they’re going to get any more money now is to win some races,” Spranger said.

This is the first time the America’s Cup has been contested away from the East Coast of the United States since the schooner America won it as the Hundred Guineas Cup in a race against 13 British boats around the Isle of Wight in 1851. There was always a suspicion that the Americans had a home-water edge, which has now gone to the Aussies. Golden Gate skipper Tom Blackaller disagrees.

“The home advantage has been overblown,” Blackaller said. “Once you’re out on the water, skill really takes over and the best yacht and crew will win.”

But will the humble prize be worth all the effort and expense?

Only to the winner.