Hundreds of intricate and crude boomerangs whizzed, hovered and whirled through the air at West Potomac Park last weekend as Benjamin Ruhe taught 200 budding boomerangers the fine art of making and throwing the crescent-shaped projectiles. It was all in preparation for the Smithsonian Institution's fourth annual open boomerang festival, slated for 3 p.m. Saturday on the West Potomac Park polo field.

"It's partly silly, partly sporting, mildly eccentric, very good exercise and best of all, fun," said Ruhe, a public affairs officer of the National Archives. He learned to throw boomerangs as a jackeroo (cowboy) in Australia during a 26-month vagabond global voyage he made 20 years ago.

"American boys throw baseballs and Australian boys throw boomerangs. It's an exciting instrument, aerodynamically beautiful and extremely challenging."

Ruhe exploded one myth about the boomerang - that it is a hunting instrument designed to return to the hunter if he misses his target.

"The returning boomerang is a porting device," he said. "Boomerangs come in many different shapes and sizes and I usually carry about 30 of my best ones with me when I go throwing, so I have short-range or long range boomerangs on hand to suit my mood."

Ruhe got the idea for a boomerang competition seven years ago when he and a friend from the Smithsonian were trying to think of ways to bring more people to the Mall.

"I suggested a boomerang throw-in as sort of a joke and the idea caught on n," chuckled Ruhe. He dug his old Australian souvenirs, sent dozens of letters around the world soliciting information, and what emerged became the first of the annual boomerang workshops.

Today Ruhe's hobby has mushroomed into a book, "Many Happy Returns," that will go on sale this month. He is official keeper of boomerang stastics for The Guiness Book of Records, has collected between 700 and 800 boomerangs, is preparing a permanent display of boomerangs for the Smithsonian Air and Space Museum and has lectured on the art of boomeranging before Boy Scout troops, Godard Space Flight Center scientists and even personnel from the Australian embassy.

Past boomerang festivals have attracted dozens of buffs from as far away as England and Australia, as well as hundreds of Washingtonians, most of whom learned the sport at Ruhe's workshops.

"The tournament is more of a fun than a serious thing," said Ruhe, adding that anyone who brings a boomerang can enter."We give awards such as the Gen. Douglas MacArthur I Shall Return Award, and there are prizes for accuracy in catching and throwing, speed in catching and number of consecutive catches."

One of Ruhe's prize pupils is David Schumm, a 22-year-old salesman from Alexandria who attracted a crowd of about 35 people early one spring morning while throwing his boomerang around the Washington Monument.

"I went into a store to buy a frisbee one day and saw some boomerangs, so I bought one of those instead," Schumm said. "Like most American-made boomerangs, it didn't fly and research at the library didn't help me find out why not.

"I called the Australian Embassy and they put me in touch with Ruhe, who broke the whole thing wide open for me," said Schumm, who now makes about 17 boomerangs a months to use, sell or give away. "They're easy to make with plywood from any lumber store, and when you make them yourself it's something special."

Other workshop boomerangers shared Schumm's enthusiasm.

"It's a sophisticated way of throwing a frisbee," said Pete Cashin, a 33-year-old District resident who bought his first boomerang as an Army man stationed in Australia. "I never really knew how to throw it right so I came to Ruhe's class and got fascinated."

"It seemed like a kind of freaky thing to do, and I'm always interested in learning to master new things," said 25-year-old Barbara Willette, and editor for the American Geophysical Union who attended Saturday's workshop.

"I want to work with aerodynamics when I grow up," said 14-year-old Pete Martone, busy sanding his boomerang. "It comes back to you - that's why I like it."

"You can make some very high-class, esoteric boomerangs if you get into the aerodynamics of it," said Bob Coakly, a 58-year-old enthusiast who has made about 50 boomerangs and will be giving a seminar on boomerangs in California later this month.

"It's cool," grinned Liz Barrer, a 26-year-old government cartographer who came to the workshop to learn how to make a lefthanded boomerang. "I think it attracts people who don't have a chance to join in big sports teams. You can do it yourself, you don't need a partner like in tennis."

"I like it because it's a good family activity," said Mead Karras, a 44-year-old Rockville housewife who turned out for the workshop with her family. "The boomerangs are fun to make, and if I can't throw it I guess I'll just turn it into a musical instrument."