The 1979 Fastnet Race, the traditional closing event of England's colorful Cowes Week yachting series, concluded Friday night, not with a trophy ceremony but with a prayer service for the dead in St. Andrew's Church here.

Eighteen persons are known to have died in a fierce storm that sprang with 70-mile-an-hour winds, upon the 306-boat fleet near Fastnet Rock in the Irish Sea, the major turning point in the 605-mile ocean race that began last Saturday. Four of the dead were aboard a boat not officially entered in the race.

Twenty-three boats were sunk or abandoned and 136 sailors rescued, 75 of them plucked by helicopters from the foaming, 25-foot seas. Only 90 boats completed the course, many of them finishing with gear damage and some with injured crew members aboard.

All week, as weary crews straggled in, they were met on the wharves of Plymouth by spectral figures emerging from the gray mist: wives of their fellow contestants. "Please, did you sight any boats out there? My husband is aboard the yacht ."

Ocean racing has many elements of naval warfare, but death at sea is not supposed to be one of them.

The sport, in fact, has traditionally had an excellent safety record. The premier long-distance races -- Newport-to-Bermuda, the TransPac, Australia's Sydney-Hobart and previous Fastnets, have never before had a drowning. Year by year the number of entries in each has risen.

An investigation has been launched here into the Fastnet disaster. The loss of so many sailors has placed a new emphasis on old questions: the suitability of boats as small as 30 feet for long offshore races; the issue of whether powerful, expensive radio equipment should be required on all yachts; the qualifications of crews and owners, the need for escort vessels, and the like. But these arguments -- though they may become bitter -- do not address the essential nature and appeal of offshore racing in sailboats.

Alan Green, secretary of the Royal Ocean Club, returned time and again last week to one theme as he met with waves of questions from 100 reporters regarding where to place blame for the events in the Irish Sea:

"Ocean racing," he said, "is a sport that concentrates on the self-sufficiency of the yachts concerned. Yachts must leave port capable of meeting any weather. It is up to the skipper to decide whether to start and whether to continue."

The importance of the test of self-sufficiency for ocean sailors is such that even a storm such as the Fastnet gale has its own appeal.

John Hogan is the skipper of the British yacht Camargue, a 40-footer that survived the Force-10 winds but retired from the race.

"We were taken by surprise by the force of the gale," Hogan said Friday, his eyes glinting. "It struck us flat against the water. After five hours it had become worse, not better, and my crew, one by one, became terrified and talked of abandoning ship.

"At one point, under bare poles, we did a death slide, mast-first down the face of a wave and turned completely upside down. On the radio during all of this we listened for a weather report, but all we could get were reports of dead men floating in the water nearby.

"But you know, having survived, I must say I would not have missed it for the world. It was prob- "TEXT OMITTED FROM SOURCE" and I am glad I was not watching television instead."

Many of the participants in this Fastnet are veterans of other famous storms, and as a result there has been much discussion of how this one compares to the others.

By consensus, it rates as the worst, in fury if not in duration.

The most infamous previous Fastnet was the 1957 race, when three separate gales swept through the fleet.

"That was very uncomfortable, because it went on for days, not just 12 hours or so," said John Coote, a British navigator who sailed this time on the American boat Toscana, a Swan 47 owned by Eric Swenson, an editor at W. W. Norton and Co. "But in those days the smaller boats sailed a shorter course, so they were spared."

Coote also sailed in the difficult Sydney-Hobart race of 1977, a race struck by what he called an "Australian Buster" wind that caused 68 retirements in a fleet of 130. "That race was lucky," Coote said. "The boats were hit on a part of the course where they were able to run for cover."

Duby Joslin, 32, a native of Newport, R.I. and veteran 12-meter crewman, remembered an Annapolis-to-Newport race of the late 1960s as almost the equal of this Fastnet.

"It's hard to compare," he said, "because on the way to Newport we had a gale on the nose for several days, and it just went on much longer. The seas weren't nearly as big as here, though. I'd say they were both lousy."

What no one yet fathom about this year's Fastnet is why so many boats went down or were abandoned in fear of imminent foundering.

It seems likely that the course of the storm was unlucky.It struck the fleet at about the half way point for many boats, near the center of the Irish Sea. The yachts had been sailing for about two days, and already had completed the coastal battle up from Cowes, through the 5-knot adverse currents of Portland Bill, and round the Scilly Isles off Land's End.

The big boats -- Jim Kilroy's 79-foot Kilaloa from California, Ted Turner's Tenacious, Condor of Bermuda, and the Australian Siska among them -- already had rounded Fastnet Rock when the gale struck. So the strongest and largest vessels had a beam reach home during the storm.

The smaller boats had to beat the windward into it, and most could not. Many were eventually blown 100 miles off course. All of the yachts lost and abandoned were under 37 feet overall.

It appears that the middle-sized boats tended to suffer from steering failure. Ten boats in the two-ton size range had broken rudders, and at least five of those rudders were built of carbon fiber. It was the failure of a new carbon fiber rudder, earlier in Cowes Week, that also put Edward Heath's Morning Cloud out of Admiral's Cup contention. It is safe to say that carbon fiber is the most maligned building material in England, as of today.

The deaths in the water are less puzzling than the failure of the boats or their crews. The sun has been seen infrequently here in recent weeks, and the air temperature is often in the 50s. Medical reports say that hypothermia (subnormal body temperature), compounded by exhaustion, was the cause of death in most of the bodies so far recovered.

In the pubs, sailors shrug in agreement at probable scenarios of tragedy.

A smaller boat is overpowered by the 70-mile-an-hour gusts. Her crew, sick and exhausted, is unable to reduce sail, or maneuver to avoid breaking seas. A crest sweeps the deck, carrying away a hatch, the vessel fills and sinks, dragging some men down by their safety harnesses. Crewmen left in the water, even in life jackets, are choked by spume or die of exposure within the hour.

Sailors have become more aware in the last year how delicate is the life of a crewman overboard. In the winter races off Florida last season, two men drowned, one after having been in the water only a few minutes.

Last week, during the hotly contested start of one day race at Cowes, the Australian boat Police Car collided with another boat with a resounding crash. Crewman John Mooney was thrown into the sea while the crews of 60 yachts looked on.

"I was just sitting there and the bow pulpit of the other yacht crashed into me and when the boats separated, she dragged me in the water," Mooney said, sitting out a dance in a Plymouth disco, his left arm in a cast.

"I was in a dazed condition. I was disoriented, and I sank very quickly. I am sure that I would have drowned had not a guy on Indigo (a nearby boat) dived in headfirst and pulled me up. It's extraordinary how fast you can drown, and everyone should know that."

Fastnet 79 probably has changed ocean racing forever. The safety record is gone now, and the possibility of disaster proven. Race committees in the future likely will impose more restrictions than before, and the sailors probably will not like it. Small boats may face new prejudice, founded or not. Expensive equipment may be demanded, some sort of crew qualification rating may be instituted.

For Britain, where sailors are made heroes in the press and knighted by the queen, this Fastnet has been a highly emotional affair. The Royal Ocean Racing Club has been blasted for failing somehow to foresee the storm. And it has been suggested that yachtsmen be required to pay the cost of their rescue.