Less maths, more sailing IRC
IRC is distinctive in its philosophy: it rewards well-sailed boats over narrowly optimised designs, balancing fairness with innovation. This analysis explores how varying race conditions shape success under IRC and why over-optimisation, while alluring, often fails to deliver consistent wins. The IRC Rule uses a confidential algorithm to assign a Time
Correction Coefficient (TCC) to each yacht. This TCC attempts to estimate a boat’s potential speed based on the key physical char- acteristics such as length, displacement, sail area and underwater appendages. The goal is not to make every race a dead heat, but to allow a wide range of designs to be competitive over time, emphasising crew skill and adaptability to the rule itself as factors in success. One of IRC’s great strengths lies in its resistance to over-optimi-
sation. Unlike other rating rules where designers can ‘game the sys- tem’, tailoring boats too precisely to rule formulas through open access to the algorithm, IRC’s own undisclosed but carefully developed algo- rithm reduces incentives for distortion. This results in a rule that, rather than rewarding ‘rule-beaters’, tends to favour seaworthy, versatile boats that perform well across the complete range of conditions. In the world of yacht racing, conditions matter deeply. Wind
strength, sea state, course and crew all influence whether a boat outperforms its rating. Design features like waterline length and sail area predict performance potential, but it is how a boat sails
ability, but especially good offshore in moderate conditions. While the temptation to ‘design to the rule’ remains, IRC has
evolved to penalise overly specialised designs. Boats optimised for a narrow performance window – such as flat-water, downwind conditions – may achieve momentary success but they struggle to win consistently. A classic example is the TP52, originally designed for windward-leeward quasi-one-design racing. Converted for IRC, TP52s often perform very well, especially in heavy-air races, but they also carry high ratings. This means even minor underperfor- mance or adverse conditions can ruin their corrected-time result. Similarly, custom-built ‘IRC weapons’ like Rán or Ichi Ban – the
latter a Botín 52 that has dominated Australian IRC racing in the past – require professional preparation and a top crew to support their high ratings. These boats are at the limit of what the rule rewards and any mistake can lead to a quick slide down the results. This reinforces IRC’s core philosophy: while a boat can be tech-
nically superior, true performance lies in consistency, adaptability and seamanship, not just raw speed or extreme design. The boats that succeed most consistently under IRC strike a
balance between performance across a wide range of conditions and course types. They are often ‘perfectly normal’; when rating their design features there is no one individual extremity but a sum of marginal gains that makes such a boat competitive in IRC. French designer Jean-Pierre Kelbert’s boats, especially the JPK
10.10, 10.80 and 11.80, are a good example of IRC-optimised versatility. Courrier Recommandé, a JPK 11.80, won the 2018 RORC Season’s Points Championship and this design continues to place highly in offshore events – with more than one 11.80 serving as the smaller boat in the 2025 Admiral’s Cup. These boats are light but not extreme, stiff without being punishing, and fast enough to compete without becoming overly reliant on specific conditions. Jeanneau’s Sun Fast 3200 and 3600 have also proved durable
under IRC. They offer an appealing mix of simplicity, speed and rating efficiency. Boats like Foggy Dew and Bellino always perform well in the RORC Offshore Series, especially in mixed conditions. In addition, the Jason Ker designs (40,43,46 etc) are also
No one understands IRC racing better than ubiquitous and very fast French skipper Géry Trentesaux. Most years he appears with another new heavily optimised IRC design, carefully selected to match both his preferred style of offshore racing as well as any new rule changes. Long Courrier (above) is this season’s weapon of choice, a modified Jason Ker-designed Sydney GTS 43. Wins this year include the Myth of Malham and North Sea races. A good bet for Rolex Fastnet 2025… which Trentesaux last won in 2015
in that day’s specific conditions that determines whether it punches above or below its TCC. Detailed ‘analyses’ by others may purport to show how wind and
course variations affect ratings, and therefore how a single-number system like IRC cannot deliver a ‘perfect’ result, but the reality is that sailing is inherently unpredictable! Weather, crew decisions, tides, all ensure that no rating system can guarantee perfect fair- ness. Moreover, the freedom IRC owners enjoy to tailor their yacht for a particular course and venue naturally balances out many of these external variables, further levelling the playing field. So why overcomplicate the sport any further? In light air smaller lower-rated boats often have an edge while
heavy or high-rated boats struggle against their rating, conditions that also reward boats with a heavier DSPL/Length ratio and low wetted surface area, often features of older or dual-purpose yachts. In contrast, during extended offshore races, or heavy-weather
events, heavier more powerful boats come into their own. Designs like the JPK 10.80, J/122 and Ker 40 can often sustain higher average speeds over long distances and handle challenging sea states better than their lighter rivals. In the 2013 Fastnet Night and Day (a JPK 10.10) won overall, not merely due to its rating but because conditions matched its design strengths: good all-round
34 SEAHORSE
consistent top performers in IRC. These ‘higher’-performance boats are notable for their fine-tuned IRC optimisation. Géry Trentesaux’s Ker 43 Long Courrier is proving to be extremely competitive this season, benefiting from lightweight construction, deep keel design and plenty of sail. But none of these designs win automatically, they require excellent crews and good race planning to realise their rating. Well-prepared cruiser-racers like the J/109 and J/122 regularly
feature on IRC podiums. Their wide availability, dependable upwind performance and strong owner networks make them formidable. The J/109 is especially potent in mid-fleet battles, where its design characteristics deliver consistent boat speed rather than raw power. One of IRC’s key strengths is that it resists becoming a blueprint-
driven game. There is no single ‘winning design’, only boats well suited to the challenges of that race on that day. A mid-sized cruiser- racer can beat a carbon-fibre race machine, given the right wind, tactical choices and crew performance. Likewise, no yacht can dom- inate every time, diversity in winners is built into the IRC system. This pragmatic and simple balance between rating and reality
fosters a healthy and inclusive racing environment. It rewards the elements that are at the heart of sailing itself: tactics, skill, reading of the weather and all-around performance. Yacht racing under the IRC rating system is a nuanced sport where conditions caninfluence success and over-optimisation can be a liability rather than an advantage. The IRC Rule remains relevant and respected because it embraces a diversity of designs while ensuring that seamanship, strategy and skill remain central to competition. From light-wind classics like the JPK 10.10 to offshore workhorses
like the Ker 40 and cruiser-racers like the J/109, the roll of IRC winners is varied. In a sport often obsessed with marginal gains, IRC is a reminder that consistency beats extremism; and that in yacht racing the right boat in the right hands, on the right day, can win. Jason Smithwick, Rating Director
q
PAUL WYETH
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150
