Above: spectacular in every way, the first Infiniti 52 DSS Tulikettu quietly at rest on the River Hamble on the evening of her launch. These internal renders particularly highlight the way in which by employing the optimum radiused rather than straight DSS foil there is surprisingly little impact on interior space. With better bearing systems the previous electric drive for the foil-control lines was dispensed with and replaced by lighter, more reliable winch power. With TP52s having proved the virtues of this size in both IRC and ORC there is now a lot of interesting development taking place outside the constraints of the TP rule itself with more offshore focus
then on top of this we can ring the changes in the sail wardrobe… and here we really get into the hard yards of determining the overall performance profile. On all of these new fast yachts having
sails that complement the potential perfor- mance profile is key. Stu Bannatyne of Doyle Sails ran this aspect of the design process for us, quite apart from also bring- ing his wide-ranging experience to all areas of the boat and how it should work. We’ve seen from the performance of
today’s two-handed fleets how much it can pay not to be carrying superfluous bodies and supplies around the racetracks, and that too applies to extra sails. So good wind range overlaps between sails are essential, able to deal with the rapid changes of TWA and TWS as these very quick boats acceler- ate and the foil effects kick in. Fewer sails and fewer changes also help
to preserve the energy levels of a smaller crew, while adding powered winches allows maximum concentration and speed of trimming to keep the boat humming. Rule changes under IRC did give us a
few hiccups along the way – the rating changes of flying headsails forced a re- evaluation of reaching configurations, while the introduction of a new lifting appendage formulation was cause for a bit
of head scratching. Fortunately it appears that the 52 just squeezed in as designed and, with the extensive analysis that had been put into all the key areas of the boat, we were eventually able to freeze the design in good time and start the build. One of the findings when having to
consider multiple rating systems was how differently the systems would look at, say, water ballast as an example. Here we found some real anomalies in the scoring of different races run under ORC and ORR, with their implied wind speeds, where these could have quite an impact on race results. One such example is illus- trated overleaf in Figure B – based on the ORR scoring of the last Bermuda Race. DSS and other lifting appendage config-
urations have also posed their problems for the rating offices – there is no simple linear correlation with wind speeds or sail- ing angles, and at this stage one can only say that the ORC treatment is possibly slightly more favourable overall than IRC. On the water, though, is where we get
the feedback to then make decisions on how to configure a new design or update of an older boat. The 46ft Maverick (cant- ing keel plus DSS) had great results under IRC in a couple of Middle Sea Races, both of which had the usual range of conditions
from drifting up the Messina Strait to full-on blast-reaching later on; and then as preparation for a crack at the Transpac she won the ORR-scored SoCal 300. Again another race of widely varying conditions. So we knew that the basic logic around
the boat was sound. Then, with the devil as usual in the detail, we ran many optimi- sation loops to arrive at a refined solution. The 52ft size has proved to be one of the
sweet spots in both currently popular rating rules and also the physics of racing yacht size ranges – so that was always going to be a good place to start the design process. There were also plenty of examples in the past where we saw the 40ft IOR One Tonners and the IOR 50s being uni- versally successful, while the intermediate 45-footers always seemed to struggle. Most of that was down to stability and
how that was derived, but these days we have more solutions and much lighter base boats that should have blurred the bound- aries; yet the 52s still stand as the bench- mark that seems to figure best in most racing around the world. Many older TP52s have now been IRC-
optimised and taken out of the TP rule, often proving extremely successful while rating a bit less and being more offshore capable than their specialist inshore sisters.
SEAHORSE 53
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