At the heart of the action
Ineos Britannia was the team of choice for sail designer JB Braun’s seventh America’s Cup foray. To be specific, Braun, who also maintained his day job as head of design and engineering at North Sails, took on the role of senior sail designer as well as being lead aero modeller for the latest Ineos campaign … as he describes to Craig Davis
JB Braun’s Cup career has taken in multiple platforms. He worked on sail designs for three eras of monohull ACC yachts in 2000, 2003 and 2007 for Young America, Stars & Stripes and Oracle. In 2010 he was involved with the Oracle-BMW Deed of Gift tri- maran programme, remaining with the US team for the foiling cat campaigns of 2013 and then 2017. Finally in 2021 he signed on with Ineos Britannia for the 2024 Cup. A long time spent in Cup World, during which literally everything has changed… As sailmakers and sail designers over the years we’ve always played second fiddle to naval architects and hull design. That’s because people can look at a hull and they can relate to the shape of a particular hull
46 SEAHORSE
form. Sails are a flexible membrane and constantly change with trim. And though the sails are the aerodynamic engine, and the only thing that drives the boat for- ward, until recently the hull was one of the features that was slowing it down. In my view the hull and sail design
should always play an equal part unless you take the hull and you move it out of the water, then it becomes an aerodynamic feature and it’s part of the horsepower of the sail package. I think what you’ve seen in the last couple of decades is the transition from what I described relating to the hull shape, to modern foiling boats with the hulls almost just an extension of the sails. The whole design space and what the
AC teams focus on have changed beyond recognition over the last few Cup cam- paigns. The big AC72 catamarans started the lesson that aerodynamics are a huge part, but ironically they were terrible aero- dynamically; they had all these lines flying around, people all sitting out in space, the crew standing up, big openings in the hulls, the cross beams… but that started the transition and got people thinking more aerodynamically. The AC50 was
another step forward in aerodynamics, but it wasn’t until the AC75 monohull where the end-plating and the connection of the lifting surfaces moved to centre stage. So today, given all the complex and
dynamic interactions in the current AC75 Cup yachts, it is unsurprising that almost everything now boils down to having the right design tools. But having got those in place you then have to trust them! It’s not as if you’re going to go out and two-boat test. It’s not as if you’re going to go out and record ‘I’m going 47kt now instead of 46.5, at this angle and that wind speed.’ It is very difficult to quantify these
differences and avoid going down rabbit holes while overlooking the whole pack- age. Take the wing keel on Australia II: it wasn’t just putting wings on the keel, it was that the keel was integrated with the hull and the centre of gravity was lower and the wings created better efficiency upwind, although it probably brought more drag downwind. Another example is the Kiwis in the last
Cup. They developed their boat and when they took it out it needed 21kt for take-off and Luna Rosa needed 18, because the foils
PAUL TODD/OUTSIDE IMAGES
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
