Port Jefferson, N.Y. — The boom swings over the wharf, hoisting aboard another coal stove bound for New England. Then, right on schedule, the schooner edges out of this snug Long Island harbor for its daily 15-mile cargo run. Once clear of the dock, it turns toward Bridgeport, Conn., and hoists sail.
Sail? In 1983?
''This is the way of the future in terms of sail power,'' says Greg Brazier, owner of the 70-foot schooner Phoenix, which has hauled cargo since late October. The twin-masted vessel depends mostly on sail, but also packs an engine for motoring in harbor and slack wind.
Mr. Brazier is one of a new breed of entrepreneur, mixing canvas and diesel power in hybrid boat designs used for everything from fishing in Pelican, Alaska , to salvage work in Norfolk, Va.
In recent years, firms in the United States, Europe, and Japan have worked on rigging tankers with sails. For example, The Shin Aitoku Maru, a 236-foot Japanese tanker, was fitted with a set of computer-controlled sails that helped hack its fuel bill in half. But with shipping firms caught in a worldwide slump, few companies seem willing or able to invest in the still-costly technology.
Sail power has never completely faded from the American scene - even in the wake of cheap fossil fuel. Chesapeake Bay oyster draggers, for example, are legally required to operate under sail.
The new wave of small sail-and-engine boats - lumped together in a group called ''sail-assisted'' vessels - can vary from vessels that depend heavily on engines, with auxiliary sails, to ships that draw most of their pulling power from canvas.
While not making a profit now, the long-term economics of Brazier's project appears promising. Since his water route trims about 60 miles from the land trip , he can charge as little as half the comparable trucking rate. His cargoes, so far, have included such sundry items as stoves, live lobsters, and an airplane propeller.
Other sail-assisted boats are already making money by combining occasional cargo hauling with other business ventures. Ron Kinsey, for instance, uses his 65-foot gaff-rigged schooner mostly for fishing in the Gulf of Mexico.
''But I also haul the odd-ball things a big boat can't,'' says the Florida-based businessman, who has carried everything from drinking water to driftwood. Later this month, he'll take a Volkswagen and a load of building supplies from Florida to a small private island in the Bahamas. His advantage, he says, is that his boat can negotiate shallow harbors where large, deep-draft vessels can't go.
Shipping experts admit sail-assisted vessels can take only a small slice of business away from engine-powered cargo boats or alternative forms of ground transportation. The biggest potential, they say, is in the use of sails on boats used strictly for fishing.
Jon Shortall, a naval architect and engineering professor at the University of South Florida, estimates there are nearly 100 sail-assisted fishing boats now in US waters, with at least 60 of those in the Pacific Northwest, Alaska, and Hawaii. Most, he says, were launched in the last four years.
The benefits in fuel savings vary, depending on the type of fishing, says Mr. Shortall, who has researched the subject. For example, Florida's snapper and grouper fishing boats could trim 30 percent on fuel using sails, he says. But crab and lobster boats - which need more pulling power - would save only 15 percent at most.
Because of the high price of fuel, observers say sail-assisted vessels have become more practical for a variety of uses. The 122-foot schooner Free Enterprise, for instance, will be operating by early summer out of Tarpon Springs, Fla., largely as a research and training vessel. Its owner, Arnold Gray , says the boat will be leased to firms for such things as seismographic research.
But the growth of hybrid sail-and-power boats isn't without snags. There's an ongoing dispute over rules for sail-assisted cargo boats. Cargo vessels - whether under sail or diesel - have to meet federal guidelines for power-driven boats.
''The Coast Guard doesn't have any rules tailored to the in-betweens - the boats that mix engine and sail,'' says Jesse Briggs, skipper of a sail-assisted tug-and-salvage boat based in Virginia. Mr. Briggs hauls personal cargoes such as tools and compressors on his boat, but is not legally permitted to carry cargo for profit.
Some would-be cargo carriers have lobbied in Washington for new guidelines that would make it easier to adapt existing sail-and-power ships to cargo uses.
Another problem, some cargo carriers say, is the potential for conflicts with longshoremen's unions.