It's crunch time for Australia's sailors as world titles and Olympic qualification go on the line off Fremantle from Saturday.

For many of the 103 Australians competing, the 2011 sailing world championships represent the last chance to secure passage to the 2012 London Games.

But competition will be fierce with more than 1200 sailors from almost 80 nations assembling with similar ambitions in the 10 Olympic classes.

Several, including three-time Laser class world champion Tom Slingsby, are certain to make the Olympic cut.

Others, like Sydney Olympic gold medallist Belinda Stowell and Beijing Olympic gold medallist Elise Rechichi, need barnstorming performances in Fremantle to qualify.

Stowell was only paired with 470 dinghy crewmate Rechichi in October but they won their first regatta four weeks later.

So embryonic is the partnership that they only took delivery of their first dinghy last week, having scrounged spare parts for a boat they borrowed for the recent national championships.

They need at least a top 10 finish at the world championships to have a chance of going to the London Games.

"To have an opportunity at 40-years-old to go to another Olympics I think is amazing," said Stowell.

"I've been dreaming of going to another Olympic Games."

Gunning for his fourth Laser world title, Slingbsy must overcome stiff competition from fierce rivals including Great Britain's Paul Goodison and Spain's Javier Hernandez.

Reigning men's world 470 champions Malcolm Page and Mathew Belcher aim to rebound from disappointment at last month's sailing World Cup round in Melbourne by beating in-form Americans Stuart McNay and Graham Biehl.

"It's certainly going to be a very intense environment, it's the last Olympic trials for a lot of countries and could be the end of an Olympic dream for many," Belcher said.

Former world champion Krystal Weir in the Laser Radial and triple Olympian RS:X sailboarder Jessica Crisp must both do well to ensure their spots at next year's Games.

The ISAF sailing world championships run between December 3-18.

Miles Godfrey
AAP