PORTLAND – Bath Iron Works notified employees Friday that it plans to lay off about 130 of them as the shipbuilder moves from designing to manufacturing the Navy’s next-generation DDG 1000 Zumwalt-class destroyer.

“We’re now beyond the peak of the DDG 1000 design effort and the high demand for these resources is declining,” said BIW President Jeffrey Geiger in an internal letter.

Despite the cuts, the company expects to hire additional production workers — perhaps several hundred — in 2011, said Jim DeMartini, spokesman for BIW.

Denny Furrow, president of the 900-member Bath Marine Draftsmen Association, said 50 of his members are expected to lose their jobs because of the cuts. Positions affected include designers, associate engineers, technical clerks and laboratory technicians.

Loren Thompson, a military analyst with the Lexington Institute in Arlington, Va., said the job cuts aren’t surprising.

“This is a common pattern as programs move from design to production,” he said. “You always get peaks and valleys — whether in shipbuilding or aircraft building.”

Furrow said he wasn’t expecting the layoffs; he thought the Navy would continue funding design work for the ship even after production started.

Thompson said it’s common for the Navy to modify designs on new ships.

“It would be logical for the Zumwalt because it is a new class of warship,” he said. “The Navy is notorious for engineering-change orders after a contract has been signed.”

Furrow said he doesn’t blame BIW for the cuts. Decisions by government contractors, he said, are largely driven by decisions in Washington.

After the layoffs the shipyard will have about 5,700 workers, more than a year ago because BIW has added 700 production workers for the Zumwalt program.

DeMartini said the shipyard, which is owned by General Dynamics, anticipates relative stability over the next two years as long as there are no changes to the Navy’s ship purchasing plans.

DeMartini said the design phase of the DDG 1000 lasted years and involved thousands of workers.

BIW started production on the first DDG 1000 in February 2009. The ships are built in sections that can weigh 3,000 to 4,000 tons each, DeMartini said.

Staff Writer Jonathan Hemmerdinger contributed to this report.