In late 2013 we received an e-mail inquiry from Italy for a design in the 60’ range. As we learned more about the client and his team, the pieces began to fit together to form a very promising and productive design opportunity. Their brief for a high performance Racer/Cruiser is always a difficult request, often compromising both sides of the equation, but this client was a little different…
Roberto Lacorte is a very dynamic person, a successful businessman who drives for the Sport Prototype racing team he sponsors, races his 2012 Vismara 47 LadyNikka as well as cruising it in summer with his family, and when he felt there was too little offshore racing in North West Italy he founded the thriving 151 Miglia race www.151miglia.it to change things. This race plus others like the Giraglia, the Rolex Middle Sea Race, and the Maxi Worlds formed the target for the new design, in a vision not just to combine racing with cruising, but to create something powerful and beautiful to do both in. The new boat had to look extraordinary as well as race effectively before being fitted out for family cruising. In cruising trim the requirements included sub-3m draft, powered winches, dinghy storage in the transom, a retracting bow thruster, and an anchor windlass, on top of the two en-suite double cabins aft and the master suite forwards. To get a feel for his options at this size Roberto chartered the 65’ Cruiser/Racer Stig for the 2013 Middle Sea Race and placed second overall as Nikka 65, showing the teams skill and learning a lot about what they wanted from a new design.
A core part of Roberto’s team is builder Alessandro Vismara, head of the large Vismara Marine facility in Viareggio where he has produced 2 of Roberto’s previous boats. The design responsibility would be a joint effort with Vismara, an experienced designer himself whose large technical office had already produced a detailed preliminary layout for SuperNikka. This allowed us to focus on our strengths in producing the external geometry for hull and deck, appendages, and rig sizing while the Vismara team produced the structures, layout, and systems. We agreed that the basic boat needed to be as aggressive as possible and concentrated on separating the racing and cruising configurations by making cruising gear removable such as the retractable bow thruster, anchor windlass, and replacing the transom door/swim step with a lighter panel, and gaining draft with a lifting keel arrangement, lowering the bulb to 4.2m. Armed with a target racing measurement condition displacement of 16,150kg and resulting weight distribution we could begin to shape the design around the requirements.
To develop the SuperNikka hull and appendages we relied on the development program originally created with performance prediction and analysis experts KND/Sailing Performance for our2014 Maxi 72’ World Champion design Alegre. This process is now a fundamental part of our performance design procedure, and begins with an analysis of the weather conditions and expected racecourse types to build a weighting matrix favouring performance in the particular conditions we want the boat to excel in. The racing event profile was Mediterranean and primarily offshore, suggesting a light/medium bias and a more even mix of wind angles than our more usual inshore event (WL) orientation. This larger reaching component favours a wider, lighter boat, with chines, and a healthy sail plan to keep moving though a quiet Med offshore night.
Working with KND partner and panel code specialist Roland Kleiter using custom aero coefficients from designers at North Sails Italy we began to analyse a range of hull shapes using the North Sails VPP. We began with a development of Alegre with soft chines well inboard, and began sequentially comparing that with more aggressive shapes using more powerful chines further outboard which proved to be very effective upwind. Over more than 20 iterations we developed the harder chined hullform until we were happy that it presented minimal negatives in the light airs more upright condition, and was clearly beneficial when heeled in a breeze.
The balance when drawing hulls of this type is firstly to try and use as much hull length especially when heeled without a wetted transom that results in a drag increase, and then to gain as much stability as possible in the powered-up heeled condition upwind and reaching without an imbalanced helm or ending up sticky as a result of too much wetted surface area upright in light airs. Boats just intended for reaching are less troubled by these issues, while boats racing on Windward/Leeward courses find that balance more difficult, explaining why hard chines aren’t common on inshore designs like TP52’s and Mini-Maxis. With a significant reaching component SuperNikka has a wide enough performance profile to make chines an attractive compromise, while retaining the need to perform in light conditions and carry added loads in cruising trim.
The North Sails VPP integrates the lift and drag solutions produced by the DasBoot panel code with the other speed producing factors such as sail area, aero coefficients, stability, etc. to produce the final performance output. Use of panel code allows a wide range of potential solutions to be evaluated more quickly thanks to a simplification of the governing equations (in essence their validity excludes boundary layer effects), but this has the tendency to over-predict powerful solutions like wide transoms and full bows. Validating the final stages of hull shape development using RANS CFD is an integral part of the process. 3D Reynolds Averaged Navier Stokes Equations RANS yield the most accurate solutions at the cost of a large volume of computation (thousands of iterations on million elements grids). In return, one can expect a very good assessment of the wave and viscous drag and catch any drag under-prediction from the panel code stages.
Using a setup developed for the KND Volvo 65 RANS program the appended model featured 10 million elements, evaluating drag, rudder angles across the range of heel, and helm balance. Appendage sizing and positioning is a major component for performance, especially upwind in light airs. In the past it was common for designs of this size to find it difficult to achieve good balance, requiring large amounts of rake to get reasonable rudder angles which is a key factor in upwind performance. Having resolved this issue during the design of Alegre we were confident regarding predicted balance, even on a relatively wide hull form with a single rudder and sizable sail plan. The RANS phase confirmed the design was on the right track with smoother stern sections, a relatively high chine aft, and moderate bow sections which produced the most promising combination in our race model.
Having originally proposed a large rig for a racer/cruiser, we agreed after discussions with the team and their North sailmaker Alessio Razeto to ensure no compromise was made with performance in light conditions, and went back to compare increased rig sizes with their rating impact. One factor in this decision was our experience that VPP’s are insensitive to the negative effects of righting moment in light conditions. This may partly be down to sailor expectations that heeling early in the light feels faster, but it seems to be backed up by experience racing in the Mediterranean that Heeling Moment and Righting Moment work best in a certain range. Our revised rig sizing moved the HM/RM relationship towards the better feel end of that band, a step made possible by the powerful hull shape being amenable to the increase in power further up the wind range.
Once the hull shape was finalised we prepared preliminary deck shapes to combine an effective Racer/Cruiser deck layout with the aesthetic demands of the client for a sleek powerful machine, in his words ‘A Missile’! At a meeting in Viareggio with Roberto and Alessandro and the other key players in the team this initial suggestion for a wide low coachroof with chines and angular cockpit sides to complement the hull shape was refined into the final configuration, allowing the boat to be effectively sailed by a range of crew numbers as well as creating a safe confined space to enjoy family sailing.
The interior is a development of Roberto’s previous LadyNikka, similarly finished with minimalist Italian style. It boasts a large open saloon with galley and desk either side of the main hatch, double guest cabins aft and a large owners cabin forwards. Carbon/foam construction incorporates many techniques and ideas from the practical and resourceful Alessandro Vismara and his team who have one of Europe’s longest track records with stylish performance Racer/Cruisers, one that perhaps is not well known outside of Italy.
SuperNikka’s first race was the 2015 151Miglia, where she romped home as first to finish ahead of larger boats and 2nd on corrected time, a great result for the team. Yet again for Mills Design the best projects exhibit a team mentality. The SuperNikka project has been one of the most pleasurable we have undertaken, working with a gifted enthusiastic owner and a very professional yard as partners. I look forward to enjoying the launching and trials with the team in March 2015, and to working with Vismara Marine on new projects in the future.
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