International A class catamaran

The A-Class Catamaran, often abbreviated to A-Cat, is a development class sailing catamaran for singlehanded racing.

The class was founded during the 1960s and was part of the 4-tier IYRU (now ISAF) approach to divide up the sports catamaran sailing scene into 4 separate groups. These A, B, C and D classes were governed by a very small set of class rules to which each design had to comply. In the beginning it was just:

All boats designed and built to these specs would be grouped into one fleet and race each other for crossing the finish line first.

The A-Class is the largest remaining of those 4 main classes. The B-Class quickly splintered into a score of sub classes like the Hobie 16's, Formula 18's and other classes that contain far more and far stricter class rules. The C-Class quickly developed into the really high tech and vanguard boats that were used in the Little America's Cup. These require immense investments of time and money to race. As a result, this class is extremely small but still maintains its status as the ultimate sailing catamaran designs. The D class never really got off the ground in earnest.

The official organisation for the A-Class catamaran is the IACA (International A division Catamarans Association).

The A-Class rules were expanded over time to prevent the cost of these boats from rising too high and to ensure fairness in racing.

Currently the main A-Class class rules are:

In handicap racing, the A-Class catamaran uses a Portsmouth Yardstick of 681 in the UK or a D-PN of 64.5 in the USA.

The A-Class design has over time converged to a single sail rig using a lightweight carbon mast of about 9 meters length and using lightweight pentex or Kevlar sailcloth. The hulls and beams are often made out of carbon fibre as well. This single sail rig (just a mainsail) allows these boats to truly excel when sailing upwind. Their lightweight and time tested sailing techniques make these boats very fast on reaches and downwind legs as well. They were often unbeatable on the race course and only with the introduction of the asymmetic spinnaker on other catamarans have they lost this position a little bit.

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Wikipedia