in this month’s ORC Column (pg26), where the modified M37 Low Noise I is used as the reference boat.
Design 50 was among the best of the light-displacement family, Design 70 represented a slightly heavier family with a higher Beam to Canoe-body-draft Ratio (BTR) and Design 73 is part of the same family but with a higher displacement to sail area ratio. This related well to what I was observing on the water when racing on Low Noise I, and that gave me the confidence to proceed in refining the concept. The final geometry comes from a refinement of Design 73, which has proved best in the initial target wind range on W/L courses. It is not extreme in any way and presents a narrow upright waterline that rapidly widens as the boat heels while pre- serving longitudinal symmetry. Appendage design in handicap racing is where the largest gains can be achieved because efficiency is mainly related to the pure draft. Therefore, once this parameter is selected the objective is to find a geo - metry with the lowest possible induced drag without compromising the ease of getting the boat to its target speeds. Numerous keel configurations were con- sidered, but the best options were keel and torpedo in a reversed T and an L configura- tion. Using RANS CFD, typical sailing conditions were simulated. Results showed good performance of the L configuration, being more efficient upwind with less drag downwind; however, taking into consider- ation the ORCi rating, the best compro- mise was achieved with a reverse T keel. The sail and rig design were carried out in close collaboration with North Sails, who made available their proprietary soft- ware for analysing three different sail plans; I was interested in investigating the efficiency related to the different distribu- tion of sail area between the mainsail and the headsails. Three sail plans with equal upwind area but with different mast loca- tions were designed and run through North’s VPP. The final comparison in terms of performance/rating highlighted the aftermost mast position as the best solution – though not by a large margin. It
was, however, finally selected because it implied lower aspect ratio jibs along with spinnakers that are easier to trim. For downwind sailing the mast and deck plan are set up for both asymmetric and symmetric sails, depending on the event. Masthead asymmetric sails on a bowsprit are favourable for IRC and off- shore racing, while symmetric fractional spinnakers are best around the cans.
Deck and interior
Generally when designing a pure racing boat there is little left over for interior volume, aesthetics and comfort, but in this case these factors had to be considered together with functionality, ergonomics and aerodynamics. On such a small boat the coachroof was mandatory to obtain enough interior height, therefore the whole deck has been developed around it. The primary need was to allow an easy and functional headsail control system while maintaining interior space. Using transverse jib tracks with up-down and in- out purchases, a quick trimming system has been achieved permitting a wide range of set-ups. The jib can be sheeted in to 5° upwind, but in a second can be dropped to 18° which is ideal when sailing the offset leg in a windward/leeward race; this has proved a particularly useful tool on these offset legs and is a weapon against com- petitors using longitudinal tracks. Interior volume is generous with an internal height of 1.8m in all the walkable areas aft of the mast. Cockpit seats and coamings give just enough comfort for four people sitting in cruise mode and significantly enlarge the interior volume without compromising racing. For cruising two additional seats can be added to allow four more people plus lots of storage. A twin-wheel steering system is also possible, preserving the functionality of the cockpit in both race and cruising modes. The hull-deck join presents a chamfered bulwark for improved aerodynamics and torsional stiffness, but most importantly for hiking comfort. The forward position of the rudder and tiller permits a good view of the telltales for the helm, who is also
positioned on the widest part of the deck for maximum righting moment. The aft position of the mainsail trimmer also benefits from maximum deck width. The interior layout was kept simple, the key objective being to keep weight concen- trated in the middle while giving all the areas enough space and comfort. There are six berths plus a proper chart table and galley. Batteries, tanks and engine are very close to the overall centre of gravity, and even the liferaft storage has been kept as central and low as possible. There is no door in the bow cabin to save weight for- ward, generating a nice open space which is handy when taking down the chutes… Aft there is a cabin on the port side and to starboard the head compartment. This interior arrangement allows enough pri- vacy when cruising but is open enough for stacking sails in offshore races. It is also possible to fit a retriever tube, particularly helpful when dousing big asymmetric kites. All the bunks and most of the furni- ture are structural to minimise element redundancy and increase stiffness. Cabin lockers are made of sail cloth and are easily removable. A laminated teak finish adds a warm touch to the interior.
Results
The first boat (Low Noise II) launched in September 2014 and started club racing in northwest Italy. The Low Noise team were very happy with her excellent performance out of the box, and her immediate collec- tion of wins was a pleasant way to begin. Together with the crew and sail designer, we worked hard over the winter to develop the whole package and find the best rig tune. At the beginning of the 2015 season Low Noise II continued its success, now against its strongest class rivals: an X35, a Grand Soleil 37 and two-time ORC world champion, the NM38 Scugnizza. Apart from the corrected time victories, it has also been gratifying to see that perfor- mance on the water is competitive enough against these bigger boats, even in strong conditions, allowing Low Noise II to take line honours on several occasions. Approaching the ORC Worlds in Barcelona we decided to set up the boat for medium air, but it turned out to be a light and often choppy event. Moreover, the high level of the crowded Class C fleet and the smaller size of our boat made this venue not exactly an easy call for the crew. However, apart from one race where a wrong sail choice proved fatal, scores were always in the top five, resulting in overall victory with a substantial 8pt margin. From a sales perspective, the boatshow season is about to begin and we have already sold five boats, two in Italy and three around Europe. The Italia 9.98 fuoriserie is also getting a lot of interest outside the pure racing field – so much so that she has been nominated for European Yacht of the Year 2016 in the performance cruiser category! Matteo Polli
SEAHORSE 43
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