The IMOCA ("Open 60") is a 60 ft (18.3 m) development class monohull sailing yacht governed by the International Monohull Open Class Association (IMOCA). The class pinnacle event are single or two person ocean races, such as the Route du Rhum and the Vendée Globe and this has been intimately linked to design development within the class. The class is recognised by World Sailing.
Class description The class is of "open" design: the boat is measurement controlled, and designers have freedom within the rules. Several parts including the mast, boom and the canting keel ram and fin are one design for safety reasons.
After several severe incidents in the early years of the class a self righting capability was introduced. Each boat must be able to self-right itself at any time. Every boat must prove this capability in a 90 degree or 180 degree test.
Dimensions Design restrictions include the hull length to be between 59 and and maximum draft of . The length including the bowsprit may not exceed 20.12 m. The max beam is 5,85 m. A maximum of four ballast tanks is allowed. Each of them has a limit in size.
Hull The IMOCAs have typically a very wide hull compared to yachts designed for coastal races. This is supposed to give more stability in wilder sea states. The mid-2000s boats had mostly a very streamlined hull optimized to create very little turbulence, thus reducing resistance.
With the introduction of foils the stresses the hull is expected to sustain changed. For one on the points where the foils are attached, secondly the contact point between hull and waves moved further back. As a result, older boats retrofitted with foils often needed also a strengthened hull. To increase performance in heavy seas scow-bows were introduced in the class. First introduced on L'Occitane these are supposed to reduce nose diving, which reduces the average speed significantly.
Cockpit The first IMOCAs had a fully open cockpit where winches and ship's wheel(s) were located. With progressing development the work area got more and more protected by a roof open to the back, sometimes also called cave. The ship's wheels were mostly replaced by different versions of tillers as autopilots took over more of the steering. In boats of the 2020 generation the first fully enclosed cockpits appeared, allowing the skippers to stay dry most of the time.
Rigging The mast of IMOCA, which is held in place by several stays is able to turn with the main sail, typically of about 180 m2. The area of the main sail can be adjusted by lowering it towards the boom, its bottom attachment. It is fully battened. To improve the performance of the mainsail the gap between boom and hull/cockpit might be closed. Charal 2 implemented this first.
Forward of the mast, most boats have at least four forestays which can carry headsails. Three of these are usually attached to the deck and, as well as bracing the mast, can carry jibs. The fourth stay runs from the mast to the tip of the bowsprit and is used for gennaker or spinnaker sails. The number of headsails that can be taken into a race is limited by most race regulations.
Appendages Two rudders and one keel are mandatory. The keel is allowed to be tilted up to 38 degrees to either side. The rudders are not allowed to have any appendages that provide lift. Certain rudder designs such as the inverted V-shape on Charal 2 are able to provide some lift.
Two other appendages are allowed, typically either hydrofoils or daggerboards. Both types of appendage are typically able to be (partially) retracted. The rake/angle of the foils can be changed up to 5 degrees.
Autopilot Each boat is equipped with an autopilot that keeps the boat going constantly to allow the skipper to turn to other tasks. The autopilot uses sensors that allow it to take into account sudden variations in apparent wind, speed, load on the foils and sails. Automated obstacle avoidance, whether it is the other ships detected by radar, AIS, or obstacles detected by the OSCAR system, which detects unknown floating objects. The data provided by the sensors allow the autopilot to steer the boat with the best wind angle and to avoid boat-breaking loads.
Rule changes under discussion Evolution of autopilot: Hydraulic control of the adjustment of the sails and the foils. For reasons of cost and maturity of technology, this track is still excluded from all the rules. However, on flying sailboats that are increasingly akin to aircraft in mechanical terms, it seems inevitable that the automated servo-controls already developed and generalized in aviation will be adapted to the world of foiling boats.
T-Rudders: Elevators in the back of the boat have been discussed. The IMOCA general assembly has voted against the introduction, most recently in October 2023.
Mast: Due to the increasing loads to the mast due to foiling, changes to the one design mast are under discussion.
History The first major sailing competition in which the Open 60s appeared was the 1986 BOC Challenge. The first boats were only limited by their length, up to 15 tons heavy and mostly constructed from aluminium.
Major milestones in the history of the IMOCA 60s:
First Vendée Globe (1989–1990) 1991: International Monohull Open Class Association founded 1998: Introduction of canting keel 2007: first Barcelona World Race 2013: one design mast and keel fin. Introduction of foils. 2018: creation of IMOCA Globe series 2023: First edition of The Ocean Race with IMOCA 60 participation.
Events +IMOCA 60 racesNameLocationSailing modeRace modeLengthThe length can vary widely between editions of the races (nautical miles)Limited to IMOCA 60CycleFirstNot necessarily with IMOCA 60 participation from startLastNotesVendée Globearound the worldsingle handednon-stop24 000yes4 years1989ongoingThe Ocean Racearound the worldcrewedstagedvaryingno4 years1973ongoingTransat Jacques Vabretransatlanticdouble handednon-stopvaryingno2 years1993ongoingRoute du Rhumsingle handednon-stop3 542no4 years1978ongoingThe TransatOriginally Single-Handed Trans-Atlantic Racetransatlanticsingle handednon-stop3 750no4 years1960ongoingRetour à la baseFormerly Transat B to Btransatlanticsingle handednon-stop3 500yesirregular2007ongoingTransat New York Vendéetransatlanticsingle handednon-stop3 600yesirregular2016ongoingRolex Fastnet RaceEuropean offshorevariousnon-stop605no2 years1925ongoingVendée ArcticEuropean offshoresingle handednon-stop1 200yesirregular2020ongoingThe Ocean Race EuropeEuropean offshorecrewedstagedvaryingnotbd2021ongoingEuropean offshorevariousnon-stop1 200yesirregular2019ongoingLe Défi AzimutEuropean offshorevariousnon-stop500yesyearly2011ongoingTrans-TasmanAustralia to New Zealandcrewednon-stop1,200noannual2026ongoingMajor former racesBarcelona World Racearound the worlddouble handednon-stopyes4 years20072015Velux 5 Oceans Racearound the worldsingle handedstagedvaryingno4 years19822011European offshorevariousnon-stopyes2 years20032007 Other races with IMOCA 60 participation:
Small races that where discontinued: ArMen Race, Grand Prix Guyader, One-time races: Monaco Globe Series, Drheam-Cup 700, Europa Warm’Up, Istanbul Europa Race, Bermudes 1000 Race - Douarnenez / Cascais, Record SNSM, Transat St Barth - Port La Forêt Races with little or occasional IMOCA 60 participation, mostly outside of the official IMOCA 60 race calendar: Round Britain & Ireland Race, Giraglia Rolex Race, Sydney to Hobart Yacht Race, Transat Québec - Saint-Malo, Newport Bermuda Race
See also Open 50 International Monohull Open Class Association (IMOCA) Vendée Globe
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