This is the big one. It's the battle of the unbeatens. It's the race Harvard has been pointing to for the whole year. It's the confrontation between Harvard, Princeton and Yale for the Goldthwaite Cup this Sunday over Princeton's beautiful Lake Carnegie course.

Because Yale should not prove to be a factor, the Harvard-Princeton clash should be a classic duel befitting the two best lightweight crews in the East. The Crimson will be out to avenge a loss to the Tigers last year that snapped Harvard's 28-race win streak extending over five years.

In that contest, a Harvard oarsman caught a massive crab in the first ten strokes of the race, leaving the Crimson a length behind with the race hardly begun. The Tigers staved off a furious Crimson charge at the finish and held on to win by the narrowest of margins, a scant .2 seconds.

The race gave the Tigers the confidence they needed and they won the Eastern Sprints Championship the following week, dethroning Harvard as the kingpin of lightweight crew, a title it had held for five straight years.

Prediction Difficult

Predicting the outcome of Sunday's race is a difficult task.

Eastern rowing coaches, in their weekly poll, chose the Crimson unanimously for first place, with Princeton in the runner-up position. However, polls don't mean anything, and the coaches' pool should only serve to psyche Princeton up even more for the race.

Analyzing comparative margins of victory against common opponents also draws a blank. Harvard beat Rutgers by six seconds, while Princeton beat the Scarlet Knights by only two seconds.

But Princeton beat Navy by 15 seconds a few weeks ago, while the Crimson could manage only a nine-second advantage over the Midshipmen last week.

Suffice it to say, the race will be tight, and in the words of number-five man Mac Heller, the winner "will be the team that rows the better race."

Wider Margins

The junior varsity should have an easier time with the Tiger J.V.s. Harvard has beaten both Navy and Rutgers by significantly wider margins than Princeton has and is at the top of the heap in the coaches' poll, with Princeton further down the list.

The J.V.s will have a new face in the lineup for the second consecutive week. Sophomore Mark Sieber, making a miraculously quick comeback from knee surgery, has moved into the number four slot, replacing R.T. Lyman, who has moved to the third varsity boat.