T.C. Williams High School of Alexandria, Va., and Georgetown University had their title dreams dashed today when superior crews rowed away from the Washington-area schools in the semifinals of the 129the Henley Royal Regatta on the River Thames.

Gusting winds and storm clouds replaced the sunshine and warm temperatures of the regatta's first two days, spreading a gloomy mist over the crews' upset chance.

Yale University sent the only two America crews into Sunday's action. Its varsity eight earned the featured Grand Challenge final and the Eli junior varsity advanced to a Ladies Challenge Plate semifinal match.

Williams coaches Jon Butler and Steve Weir hoped for a tailwind to aid their Princess Elizabeth Challenge cup effort against Ridley College High School of St. Catharines, Ontaio. Ridley, averaging 6-foot-3 and nearly 180 pounds per man, had defeated the Titans by 1 1/2 lengths in the scholastic Rowing Association of America Regatta in May and looked even stronger in demolished its first two opponents here.

Williams employed an extreme tactic of bolting from the stake boats with a power-10 (10 strokes at maximum effort), then settling for 10 strokes before another power-10. The intent was to gain a quick lead on the Canadian crew, trying to force it into erring in a catch-up try. The maneuver failed to stop Riley from taking a length lead after a quarter mile, and extending it to two lengths at the quarter point and three lengths at the midpoint of the one-mile, 550-yard course. Ridley finished easily in 7:11.

"Since only one crew gets to race tomorrow, we had to try something," Butler commented. "They were just a lot stronger than us, a lot faster than us. We didn't seem to make any mistakes. They just rowed away from us."

Georgetown found its straight four of bowman Mark Wessel, Peter Radell, David McAneny and stroke Jim Costello down by the three-quarters of a length after a quarter-mile against the Lady Margaret Boat Club of Cambridge, England, in their Visitors' Cup Race. Lady Margaret increased its lead to more than a length at the half-way mark, then held off a mild Georgetown comeback before increasing its lead to 2 1/2 lengths after one mile and 3 1/3 lengths at the finish.

Georgetown rowed steadily at about 36 stokes per minute after its start but could not match the power of Lady Margaret.

"We would have liked to have gone farther, but we're not falling apart or anything," McAneny said. We're very proud to have made the final four. This has been the greatest week of my life."

"They rowed as well as I've ever seen them row. It just wasn't enough," Coach Greg Carroll said.

Yale spotted Oxford University two-thirds of a length lead off the start before storming to a three-length victory in its Grand Challenge semifinal in 6:35. Still, the Elis will be hard-pressed to gain the Cup Sunday in its match against the London and Thames Tradesman Boat Club eight, which also serves as the British national team.

The Britons shot to a 1 1/2-length lead off the start against the University of California-Berkeley and cruised in open water unchallenged in 6:48.

Yale's junior varsity, stroked by David Potter of Vienna, Va., had an easy time disposing of Trinity Hall College of Cambridge, to advance to a Sunday semifinal against London University. The winner of that contest will race later that afternoon for the plate against the victory of the match between Reading University of England and Downing College of Cambridge.

The Yale lightweights, with Matthew Broder of Arlington, Va., stroking from the seventh seat, fell victim to the heavyweight eight from Henleyhs Leander Boat Club by more than four lengths in a Thames Challenge Cup quarterfinal. The Yale straight pair of Hal Evans and Ed Chandler lost by 3 1/2 lengths to J.W. Woodhouse and J. S. Palmer of Cambridge University in a semifinal for the Silver Goblets and Nickalls' Challenge Cup.