Opposite: he would never say it himself, but right now Tom Slingsby can lay good claim to being the world’s no1 ranked sailor. Indeed, if the much hyped prospect turns out to be real, of a triumvirate of Slingsby, Paul Goodison and Terry Hutchinson on point for the next American Magic Cup campaign, then we might put down some of our own money on the New York YC finally getting their trophy back. We shall see. Having won the Cup with Oracle in 2013, Slingsby is today schooling all his America’s Cup rivals in the Sail GP series as skipper of Team Australia while also making Cup winners Burling and Tuke look rank amateurs by comparison. In winning the 2021 Moth Worlds at Garda (here) on his Bieker Moth Slingsby took 13 of the 14 races, discarding a 1st and 2nd place – while at the end of the regatta the Mackay-built Bieker Moths had filled the top six places overall. As well as ‘macro’ improvements, including much deeper foils (left) to increase righting moment, the much finessed new design features beautiful detailing with every effort made to keep the package aerodynamically clean in every area. The FEA model (above) shows where all the heavy structural lifting is done when the boat is fully cranked up at the point of maximum dynamic righting moment… not in the bow, that’s for sure
what made it to the water would be as close as possible to what we designed. America’s Cup campaigns use hundreds
of thousands of dollars of computer analysis to fine-tune the aero and hydrodynamics of their boats and foils. Our Moth effort had very limited access to these sorts of tools. We had a bit of RANS analysis help on the lifting foils from Nicolas Rousselon, plus I was able to use a Rhino plug-in called OrcaCFD to do some simple analysis of hull takeoff. The aero-related shaping of the hull and hiking wings was done by eye (although I have been able to use another Rhino plug-in called Rhino Flow RT to do some RANS aero analysis).
Hull and wings It is tempting to pare the volume of the hull down as much as possible in an effort to minimise aerodynamic drag but this has
to be balanced against the reality of need- ing to float a wide range of crew weights. This has become more challenging as
the median competitive crew weight and apparent wind speeds continue to increase hand in hand (that ‘might makes right’ thing). I took a step towards a smaller hull – reducing the stem height by around 50mm compared to the Exocet and remov- ing the foredeck (substantially reducing frontal area and greatly improving flow around the base of the mainsail). Rather than using a chined hull shape
like the Mach 2 I chose a more rounded hull shape (again like the Exocet). The thought behind this was that the better straightline aerodynamics of a rounded hull would outweigh the improved takeoff of a chined hull. I think the future will see further reductions in hull volume but there will be some drawbacks to this path.
Having pared down the hull I went after
the hiking wings. If you look at the Moth from a nominal apparent wind angle it is pretty clear that the hiking wings are a substantial proportion of the frontal area and surface area of the hull/hiking wing package. I’ve always been puzzled by why typical Moth wings extend all the way to the stern. Anyone familiar with hydrofoil boats (or even paper airplanes) knows that there is a real limit to how far aft you can position the weight before the package becomes seriously unstable in pitch. With that in mind I took a stab at min-
imising the fore and aft extent of the racks. Even though this provides the crew with less grovelling space aft as they endeavour to get around the deck-sweeper in manoeuvres I think the aero gain is well worth the inconvenience. In addition to reducing the fore and aft extent of the
SEAHORSE 51
MACKAY BOATS
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
