While a small group of striking steelworkers picketed outside that gates today at the Newport News Shipbuilding and Dry Dock Co., a prinate party inside launched the largest ship ever built in the western hemisphere.

The UST Atlantic, a tanker built by the company for Shell Oil and poerated by Interocean Managenent Corp., slid into the waters of the Chesapeake Bay after Elizabeth Kemp Renner took four whacks before cracking a champagne bottle across the ship's bow.

The United Steelworkers of America Cocal 8888 picketed the shipbuilding company for the fourth day today as nether side appeared ready to give way to the other's demads.

"There were probably 20 or 30 outside the gate as I drove through, "but there were no incidents," company spodesman Jim Griffith said.

Eighteen steelworkers have been arrested during the strike, including three presons charged with assaulting policemen on picket lines, officials said.

"The police have practically got our guys under sidewalk arrest," union spokesman Bill Edwards said. "Sometimes they have more police down there than our pickets."

Shipyard chairman Ralph Cousins made only an oblique reference to the strike when he welcomed guests "on behalf of all the employes, or almost all the employes" of the yard.

A test of the steelworkers' clout is expected Monday when strikers will pick up paychecks for work performed before the walkout Jan. 31. After that, they will not be paid unless the strike ends or they cross the picket lines, as some already have done.

"Monday is the big test. It's critical... we'll definitely have our pickets out there in great strength," said union spokesman Edwards.

The UST Atlantic, 1,187 feet long with a 95-foot draft and a 228-foot beam, was built by private contract. The company said that if the ship were stood on end, it would be the fourth highest structure in the United States.

In the water during the christening was a smaller boat, carrying the "navy" of the steelworkers, Edwards said.

Edward said most of the pickets today were ship designers, members of USWA Local 8417, who have been on strike against the company for almost two years.

Local 8888, representing 15,500 blue collar workers at the yard, is striking in an effort to force the company to recognize ir force the company to recognize it as the bargaining agent for the workers.

The shipyard has vowed not to recognize the steelworkers pending an appeal of last year's union representation election. The appeal is scheduled to be heard March 7, although the company, Gov. John N. Dalton and Attorney General J. Marshall Coleman have petitioned the 4th U.S. Circuit Court of Appeals for an earlier hearing.