Japan sails ahead toward fleet of wind-powered ships

The first vessel in a 21st-century generation of sailing ships is slowly taking shape at a shipyard near here. But the 26,000-ton sail-rigged motor bulk carrier probably will not please the purists - it bears little resemblance to the majestic and romantic 19 th-century tea clippers, for example.

There will be no plethora of sails with quaint names. The handful of tiny sails, made from synthetic materials, will be controlled by computerized deck instruments constantly monitoring wind speed and direction. In fact, the sails will be a source of auxiliary power rather than a main driving force. They are designed to supplement the engines under the right conditions and to reduce fuel consumption.

Japanese experts say the combination of motor power and sail power makes good economic sense. The planned bulk carrier will likely be able to cut its energy consumption by half compared to the most fuel-efficient conventional ships. This follows the lessons learned from the successful operations of a pioneering 1,600 -ton sail-motor tanker built in 1980 for the domestic coastal trade. A 2,100-ton cargo ship was launched this March to carry steel products along the coast. A sister ship is under construction.

Conventional sailing ships have to run a zigzag course. But the oil tanker Shin Aitoku Maru proved that it is possible to run a straight line, keeping to a timetable regardless of wind conditions.

''You might think that the larger the sail area, the more the ship can utilize wind force. But the Shin Aitoku Maru proved the opposite is true,'' said Noburu Hamada, president of the Japan Ship Machinery Development Association.

''A ship with large sails will never travel straight. We have established that a vessel with a minimal area of sail as auxiliary equipment will move straight and have good stability.''

The famous tea clipper Cutty Sark, for example, had a total sail area of 2, 400 square meters. The Shin Aitoku Maru gets by nicely with no more than 200 square meters. ''At first, our designers thought the sails were too small,'' Hamada recalled. ''But, in fact, we found the ship could travel much faster with less.''

As a result, the bulk carrier now being built will carry only two sails, each some 400 to 500 square meters. Past experience shows this should be sufficient to propel the ship 1.3 to 1.7 times faster than with full engine power alone. Also, the engine speed can be reduced to save fuel.

If this proves successful, there is talk of developing large passenger liners with the same sail/motor combination.

Japan is not alone in looking backward to go forward at sea. Britain plans a 1,600-ton tanker by the end of 1984, and shipbuilders in the United States, West Germany, Belgium, and the Soviet Union are reported to be joining the move back to sail power in the interests of fuel conservation.

The Soviets are said to be considering a 50,000-ton ship with seven sails, the Americans a 28,000-ton vessel with five sails - compared to the two being fitted to the comparable Japanese ship.

No one has got as far as the Japanese in building ships and getting the most out of minimum sails. The two small ships already launched are to be followed by four more over the next three months before the big leap forward into oceangoing vessels.