Vadlau, who starts with a 13-point advantage over Constanze Stolz (GER), knows she only has to stay out of trouble to finish on top.
"I will not risk very much," she admitted.
Stolz said: "Lara has so much distance on me, I am happy for her to win gold."
US Virgin Islands Byte sailor Ian Barrows starts the boys medal race with a 12-point advantage over Germany's Florian Haufe.
"I am just going to take it like a normal race and stay near the other guys I need to stick around to make sure they do not get too far ahead, " said Barrows.
Israel's Mayan Rafic leads the boys windsurfers and has promised to "sleep early and eat good" in his quest for gold.
Rafic will start eight points ahead of Hong Kong's Michael Cheng.
"I'll have an eye on Hong Kong, but I'll try and concentrate on myself and do my best," said Rafic.
Cheng needs a big swing to take gold but will be looking over his shoulder at Kieran Martin (GBR), who is a further five points behind, and Kim Chaneui (KOR), who will hope to overcome a single point deficit to get into a medal position.
Girls windsurfer Siripon Kaewduang-Ngam (THA) begins the medal race on 18 points after a sparkling series. She has won all but three of her 10 races so far and has never finished outside the top
The real battle is for second place with Veronica Fanciulli (ITA), Naomi Cohen (ISR) and Valentina Serigos (ARG) all on 38 points, a full 20 points behind the leader.
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