Here’s a Nonstop Challenge : Sailing: 12 solo sailors will attempt to race around the world without stopping and with no outside assistance.

Twelve solo sailors will leave this port Sunday in the Globe Challenge nonstop race around the world.

Among them is one American, Mike Plant, 39, of Newport, R.I., the Class 2 winner of the 1986-87 BOC Challenge solo race around the world. The BOC race has three stops. The Globe Challenge none.

The Globe Challenge is the brainchild of Philippe Jeantot, 37, twice winner of the BOC Challenge.

In all his races, Jeantot has been sponsored by Credit Agricole--or, the Farmer’s Bank--one of the largest banking institutions in the world.

As a result, there was muttering in each of the BOC races about Jeantot’s deep-pockets sponsor.

Perhaps because of that, Jeantot conceived the idea of a nonstop race with no outside assistance once under way. He saw no practical way to limit the amount of money spent on the 60-foot, high-tech sailboats entered in the race. But eliminating assistance after the start would be a great equalizer.

No assistance means that a boat can anchor offshore or in port, but it cannot tie up to a dock or another boat. The skipper cannot leave the boat and must do all repairs himself with parts already on board.

This means that if a mast breaks, the boat is out of the race unless the solo sailor can figure out a way to jury-rig another.

Direct medical assistance is also curtailed. Elaborate first-aid kits have been prepared for the participants and the race has an official doctor to respond to emergencies by radio.

But a doctor can only be seen at certain check points established for the race--the Canary Islands, the Cape Verde Islands, Auckland Island south of New Zealand, and Cape Horn.

If a medical problem requires a doctor’s attention any other time, the sailor will have to drop out of the race to get it.

Only one other solo nonstop race around the world has been run, the Golden Globe race 20 years ago. Its only rule was that the boats had to start from a port, any port, on the south coast of England.

Only one boat finished, Suhaili, a 32-foot ketch sailed by Robin Knox-Johnston of Britain. Suhaili covered 30,123 nautical miles in 313 days.

Jeantot estimates that the winner of the Globe Challenge will finish in 120 days. The course is 25,000 nautical miles, about 2,000 miles shorter than the BOC Challenge with its stopover course diversions. The winning BOC time was 134 days.

Jeantot had hoped to make this race a truly international event. And for a while it looked as though it would be. Boats signed up or indicated interest from a score of countries. But when entries closed there were just a dozen boats, 10 of them French.

Besides Plant, the other non-Frenchman is Bertie Reed, 46, of South Africa. Reed, too, is a veteran BOC Challenge racer, having finished second to Jeantot in the 1982-83 event.

If only one American can be in this race, the nation would be hard pressed to find a better representative than Plant.

First, there is his Class 2 win in the last BOC Challenge, in which he took his 50-foot Airco cutter around the world in 156 days.

Then, there was his tenacity over the past two years to get a boat built for the Globe Challenge.

With little money of his own, Plant put together a small group of supporters in his native Minnesota that came up with enough money to get the $700,000 boat construction project started in a Newport yard.

But as late as last June, there was serious doubt that he would make it. The launch was delayed for lack of money. At the last minute, Duracell, the battery manufacturer, contributed $250,000, a record sum for an American firm to commit to an ocean solo-sailing participant.

Plant went to Rodger Martin for the design of Duracell, his 60-foot sloop. Martin had designed Airco, the BOC class winner.

The result is a 27,500-pound craft with a 70-foot mast that crossed the Atlantic to this race starting port, a distance of 3,400 miles, in less than15 days. The passage time let everyone here know that Duracell was a serious contender.

But the competition is tough.

The French boating press sees the race as a contest between Jeantot and fellow Frenchman Philippe Poupon, 34. Poupon has been ocean racing since he was 20. He has raced around the world on crewed boats twice and has won five trans-Atlantic solo races. In 1987, he set a west-to-east trans-Atlantic record on a crewed catamaran of 7 days 12 hours.

Poupon has a bone of sorts to pick with Jeantot. In the 1984 solo trans-Atlantic race, Jeantot capsized in his catamaran about 1,500 miles from the start in England.

Another racer, Yvon Fauconnier, stood by Jeantot and his capsized boat until it was certain help was on the way.

Poupon, meanwhile, was first across the finish line at Newport, R.I., in 16 days 11 hours. But he wasn’t the winner. Fauconnier was--after the race committee gave him an allowance for time spent standing by Jeantot.

Another competitor that can’t be overlooked is Titouan Lamazou, 33, also a BOC Challenge veteran. Lamazou lost his automatic steering on the first leg of the 1986-87 BOC and was forced to hand-steer for five weeks to reach Cape Town.

Despite the setback, he finished only three days behind Jeantot. Had he not been slowed by the autopilot failure on the first leg, it’s probable that he would have won the race.

The race organizers are taking pains to stay in touch with the racers for their safety and to satisfy the media requirements for information.

Each boat will be equipped with a transponder, part of a satellite tracking system called Argos. The system will provide headquarters with position reports on each of the boats up to six times a day. The transponder also has an emergency signal switch that the skipper can turn on if he is trouble.

The course runs close to a number of islands in the Atlantic, Indian and Pacific oceans.

Observers wonder if Jeantot is correct in estimating a 120-day finishing time. He based the estimate on his BOC Challenge performance. But in that race he had stops to make repairs.

In fact, at one stop, Sydney, Australia, he had to re-secure the keel to his boat. It had broken several keel bolts and forced him to pump 100 gallons an hour out of his hull during the last several days of the race leg.

No such major repairs can be made in the Globe Challenge. A good guess would be that more than half the boats will not finish.

And the winner may be the skipper who can keep a seriously damaged boat going at much reduced speed, limping into port here and to victory in substantially more than 120 days.