Open 60s are a class of racing boats designed for single-handed or double-handed offshore racing.
The rules are a maximum of 60' long and 14.5' depth. Their beam and height of mast can be whatever the designer and sailor want. Numerous stability and safety regulations apply. They generally are built of carbon fibre for strength and lightness, with twin daggerboards, twin rudders, and a canting keel. They are designed to be as light as possible (for speed) but strong enough to withstand terrible storms at sea.
They are designed from the outset to be sailed just one person. There are very few comforts aboard, and she will spend most of the time in the 'crash' seats in a cuddy that separates the open cockpit and deck from the Navigation work station. This is the nerve system, packed with electronics and computer equipment to help navigate, check performance, and communicate.
The boat has a number of different sails to suit various conditions - not as many sails as a boat designed to be sailed by a 12 strong crew, but enough to keep the solo skipper working hard all the time matching sailplan to wind and sea conditions. There are three types of sails - a mainsail, headsails on furlers (rolled up around the stays) and a spinnaker - although alone, the spinnaker is only used in very stable conditions (to be caught in a squall with this huge balloon of sail could mean disaster - end of race).
The boats also have to prove their ability to turn themselves the right way up if they become knocked down or turn upside down. This is part of the latest IMOCA safety rules which require the boat to right without the assistance of waves by the skipper taking some action to turn the boat over.
[Source: http://www.imoca.org/uk/]