The Charles will become the rowing mecca of the world Sunday when more than 3200 oarsmen ply the river in the 15th Head of the Charles Regatta before an expected 60,000 spectators.

From 9:30 a.m. to 4:30 p.m., about 720 boats, starting at 10 to 15 second intervals, will sprint away from the Boston University bridge towards their goal, the Cambridge Boat Club, three miles away.

Those three miles provide a spectacle that is as beautiful as it is chaotic; the sleek shells glide through the water in close and uneasy proximity to one another, and to more formidable obstacles--like bridges and the river bank.

In the intensely competitive world of rowing, the Head rates as more of an afternoon for enjoyment more than Every year the organizers award the Paul Revere Point Trophy to the organization--both colleges and clubs compete--that amasses the most points in the 18 different events, but oarsmen concede the medium, not the metal, is the message of the Head.

Last year Harvard snatched the team trophy, nipping Yale and the University of Pennsylvania despite a surprising seventh-place finish by th men's heavyweights in the concluding event of the regatta.

Indeed, the heavies usually use the Head to experiment with unusual combinations, and last year, with a particular boat, the state-of-the-art molded Robinson plastic shell. Again this year the emphasis will be on giving newcomers a try, as coach Harry Parker will let returning varsity veterans Jay Smith John MacEchern and Charlie Altekruse row in events other than the varsity eight. Altekruse and George Hatch--back after a year off-will compete together in championship double sculls.

Competition for the finest viewing spots--and for the most decadent tailgate--often proves almost as fierce as for the medals. Any of the six bridges under which the racers pass--B.U., River St., Western Ave., Anderson, Eliot and especially the Weeks Footbridge--draw the best reviews. Auto-racing fans, however, gravitate toward Eliot. as the tricky curve that preceeds it often causes watery carnage.

All manner of rowing events will be on display, from the veteran single scullers (50 years old and over) who open the festivities to various combinations of two, four and eight rowers, including the mixed eights, four men and four women, at 2:55 p.m.