Unbeaten in a major regatta in four years, Kiwi 49er pair Peter Burling and Blair Tuke will kick off their bid for the ultimate prize tomorrow morning: Olympic gold.

The impressive duo were surprise silver medallists at the London Olympics four years ago. This time they are the clear favourites heading into the Rio regatta having dominated the fleet since the last Olympiad.

The 2015 ISAF world sailors of the year have won the past four world championships in the class, an amassed a run 27 straight wins before being tipped over in a warm-up event in Rio last month.

Here's what you need to know:
- The 49er is a double-handed skiff
- It is the most high-performance boat of all the Olympic classes
- Both of the crew are equipped with their own trapeze and sailing is handled while "flying"
- While it is a one-design class, there are speed advantages to be gained through tuning the boat


Starting today, 20 crews from 20 different countries will complete 12 races - three each day. First place in each event gets one point, second two points and so on. After 10 races, the top 10 crews will advance through to the medal race, which carries double points. The medal race will be held on Friday August 19 (NZT).

Burling and Tuke's main rivals are the Australian pair of Nathan Outteridge and Iain Jensen, who topped the podium at the London Olympics four years ago. The young Kiwis have dominated their former training partners since the last Olympiad, winning the past four world champions, and racking up an incredible winning streak of 27 consecutive regattas - an unprecedented record in sailing. But the Australians brought that winning streak to an unexpected end in the final warm-up event before the Olympics, defeating Burling and Tuke at the South American Championships last month.

The Kiwis weren't too bothered by the result, maintaining the only win they have ever been focused on is claiming gold in Rio. But the win gave the Australians a healthy confidence boost ahead of the big showdown.

"It was good to finally break the streak of the Kiwis. We've felt like we've been improving over the last year and it's good to have some validation that we're closing the gap. I hope we can continue that way and bring home a good result for the Games. On shore we are still good friends, joke around, have a chat and stuff but there's no love lost between us on the water," said Jensen.

Your guide to what the commentators will be saying...
Port: When looking forwards, the lefthand side of the boat.
Starboard: When looking forwards, the righthand side of the boat.
Beat: How sailors make progress against the wind by sailing in a zig-zag.
Run: The downwind legs of the race.