Boats to fit the challenge

Winning design: Team NZ had things right in 2000

The America's Cup was changed forever by a controversial episode in 1988.

In that year, holders Team Dennis Conner answered a New Zealand challenge with a giant catamaran and the event descended into a succession of court battles.

Feature: America's Cup controversy

A ruling found in favour of the successful US syndicate, but the lopsided spectacle led to the standardisation of boats under America's Cup Class specifications, which still hold today.

One complex formula has been honed to keep the racing 'even-keeled' for boats of different weights and designs.

Guide to an America's Cup boat

It basically offsets speed-gain factors - like boat length or sail area - against speed loss factors - such as water displacement or weight.

So, for example, an extra square inch of sail may have to be offset by extra weight.

There are some additional guide-lines.

Dennis Conner caused controversy in 1988

Weight is limited to the 16-25 tonne range, and there are also limits at each end of the design range for length and sail area.

The maximum beam (width) is 5.5 metres, but, since 1995, all boats have been designed well under that measurement.

The narrow and heavy 1992 defender America3 appears to be a well-used model.

Despite reduced stability, narrow boats like this have proved particularly fast upwind.

America's Cup entries have also tended to be heavy in recent campaigns, because this allows for increases in length and sail that more than compensate for the slowing effect of the extra weight.

The formula is in place to encourage diverse designs but to keep racing competitive.

But many argue that it is breeding similarity of boats instead, providing less scope for a new revolutionary approach to boat design.

Only time will tell if this school of thought holds true this time around.