Bob Froehlich had heard the rumors; in the place he works there's a fresh batch every week. This time they were about him. Yesterday they came true.

"From the time I was 17 years old I've been breaking my a -- trying to make it," said Froehlich, 30, a homeowner and father of two, who made $12.03 an hour as a Plexiglas assembler at the Fairchild Republic aerospace plant here. "It was just starting to get easy. Now this."

"This" was a layoff, and they have been coming each Friday like clockwork at Fairchild since last December.

So far 1,300 workers at the Long Island plant here and another 600 at the Hagerstown, Md., plant have lost their jobs, a total of 21 percent of the company's work force.

In a year of 10 percent unemployment there is nothing novel, of course, about layoffs.

But it is a bit baffling to encounter it here, in an outpost of the nation's military-industrial complex.

Fairchild is a self-described peewee among giants in the defense industry, and somehow the Reagan administration's military buildup has passed it by, catching it betwixt and between.

The Air Force contract that has been its meal ticket for the past five years -- the A10 anti-tank fighter plane -- is winding down; its next large project, the NGT trainer plane, will not go into full production for several years.

Some others in the aerospace industry are hurting as much as Fairchild, but for a different reason.

They invested heavily in civilian production, and have watched their sales fall victim to high interest rates, the recession and foreign competition.

Fairchild is one of the few to suffer because of the defense budget, and its workers are frankly baffled.

"Ever since Reagan got in, all I'm hearing is defense, defense, defense," said Gene LaFerlita, president of the International Association of Machinists and Aerospace Workers, Lodge 1987, which represents Fairchild's blue-collar employes.

"We expected a boom. Anybody would. My question is, 'where did all the money go?' "

LaFerlita says he has trouble convincing other union leaders how badly his membership is hurting. "They all tell me, 'we're doin' bad but you must be okay.' They want to know if I can find work for their people."

LaFerlita, whose union is among the most liberal in the country, would like to believe that the bafflement and dashed expectations of his membership have generated a backlash against Reagan. But he is a realist, so he's frankly not sure.

"Let's face it: the union voter today is pretty independent," he said. "Whether they take this out on the Republicans, I just don't know."

Among the workers at Fairchild, there is plenty of talk about politics these days -- but not in the partisan or ideological sense. It is about the politics of good connections, about the politics that drive a bureaucracy. One worker, sipping an eight-ounce Budweiser during his lunch break outside the plant yesterday, had the following explanation for Fairchild's woes:

"Go over to Grumman," a major defense contractor headquartered a few miles from here. "You see the politicians coming in and out all the time. We just don't have the right connections."

Another luncher, Anthony Papaleo, a machinist with 30 years' experience, saw the enemy in the Air Force bureaucracy. "The A10 isn't a flashy plane, and it isn't a fast plane. The Air Force can't get their 25-year-old jet jockeys to want to fly the thing."

The other kind of politics, the Democrat and Republican kind, rarely comes up with these workers. Thomas Bonanno, 54, is a structural mechanic who was laid off from his $11.30-an-hour job two weeks ago. He hasn't found work yet, and expects to draw his first unemployment check of $125 a week soon. There are no supplemental union benefits.

Bonanno voted for Reagan two years ago. He finds "something definitely cockeyed" in the fact that his employer has not profited from the president's military buildup. Does he hold Reagan responsible?

"Not really," he said. "I think he's doing a pretty fair job. The Democrats are going to try to needle him with the 10 percent unemployment, but he's done okay."

Bonanno is a living example of what is frustrating Democrats this year -- the "patience gap" of the voters.

The local Democrats are guarding themselves against the phenomenon. "People like Ronald Reagan and they let him get away with murder," said Rep. Thomas Downey (D-N.Y.), a liberal whose district covers the Fairchild factory.

"When I campaign I don't make him the issue. If I did I'd be in trouble. I want to make this a referendum on me." Downey's district has an unemployment rate of 6.5 percent, well below the national average. "It's not a driving issue here the way it is in Ohio or Indiana," he said.

For the personal lives of the unemployed, of course, it makes all the difference in the world, no matter where they live. Froehlich, the fourth generation in his family to work the lines at Fairchild, doesn't think there is much market for his skills "on the outside."

He expects eventually to find work. But it won't be the same. "I'll get something -- laying sewer pipes, digging ditches, something. But it will be for about half of what I'm making now."