Preseason training for Artemis Racing ended abruptly and tragically nearly three months ago. Next week, with no more than eight days of practice on its new boat, the season begins. Its opponent has had roughly 80 days on its boat. The knockout stages of America's Cup racing begin Tuesday at 1:15 p.m. when the Swedish team emerges from a long period of mourning and boat construction to sail against Italy's Luna Rossa Challenge in the semifinals of the Louis Vuitton Cup. The best-of-seven event in the challenger series is scheduled to continue Wednesday, Friday and Saturday. If necessary, the final three races will take place Aug. 12, 13 and 15. All the races begin at 1:15 p.m.