Left: robust but wet as the Volvo 65 Vestas 11th Hour Racing leaves Cape Town at the start of leg 2 in the last round-the-world race at the end of 2017. Vestas was skippered in the last race by American Charlie Enright who is back to lead the 11th Hour entry this time – now racing a new Imoca (above) which promises to be not only a lot faster off the wind than his previous steed but also, remarkably, a lot drier, with most of the sailing operations being done from inside the boat (and with a great deal of attention having been paid to keeping that inside as dry as possible). The team’s Verdier-designed 60-footer is the only Imoca in the five-boat line-up to have been specifically built for crewed sailing; that said, when the boat returned from the last TJV a lot of the equipment for a full crew which had been taken off for the two-handed transat stayed in the container. It seems the Imoca has reached a stage of refinement where the ergonomics are so good that all extra crew really bring is an ability to push harder for longer… while trying not to break the boat
consolidated to try to arrive at a hull design that was the best possible balance between performance in specific condi- tions versus trying to create the best all- rounder. A balance that we have hopefully got right despite the racecourse, autopilot rule and crew configuration all having changed since we committed to our hull design an age ago back in 2020… With the introduction of foils into the
equation, however, the hull shape is no longer the performance driver it once was. The difference between foil designs can
be measured in knots when compared to the fractions of a knot we were previously trying to find in the hulls, so you cannot understate the importance of getting these right. There is also a huge amount of free- dom in the shape of foils, as evidenced in the wide range of designs currently visible in the class. Size, shape, section and where they exit the hull are all critical decisions.
Plus with foils weighing close to 300kg,
built in solid carbon, and with a design and build process taking approximately six months, any mistakes in this area could be brutally expensive in time and money. With this in mind the simulator has become another key element in the design process. The foils generate a still, to me, remark-
able amount of dynamic righting moment as well as lifting us clear of the water and ‘reducing’ displacement. However, we don’t currently have the luxury of eleva- tors on Imoca rudders which at times means that these boats can become more than a handful to control. In addition to aiding with design, the
simulator has also been a powerful tool to fast-track our learning, helping us to understand how the physics of the boat works and how the many different levers can be pulled to gain performance in wide- ranging conditions, whether it is from
more foil lift, aero power, water ballast or keel angle. The list goes on. There is no doubt these boats are far
more complex than either the VO65s or the VO70s I have sailed previously. Guil- laume’s methodology and experience from the America’s Cup, his Velocity Prediction Program (VPP) and the simulator allowed us to work our way through a great number of candidate foils and experiment with all manner of crazy ideas to try to identify the right compromise between ultimate performance and ‘user-tolerance’, to deliver a package that works effectively in the real world and over extended periods. The predicted performance suggested by
the VPP typically represents the fastest speeds that can be achieved in the lowest drag configuration but, with waves, gusts and the instability of the real world, this sort of performance isn’t always realistic. However, the simulator has proved to be a
SEAHORSE 35
AMORY ROSS
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
