existing Js, and the five that performed best were then run through a Computa- tional Fluid Dynamics (CFD) program to see if the results we found in the VPP reflected those in CFD.
Even within our family of larger Js, the differences between the various designs in length, beam, volume distribution, wetted surface and keel shapes were considerable. These designs were then also run through the JCA’s own handicapping system to determine which design was optimal on corrected time. The results showed that certain designs performed better in light air, others in heavy air and, notably, several behaved very differently in waves. JH1 Lionheart was eventually chosen, a design based on the lines of one of the Ranger syndicate designs made in 1936, but never built. The IP rights for this design were bought and the team got to work on how the design could be optimised within the rules. This began with her aluminium structure which was run through a Finite Element Program to optimise longitudinal stiffness at high runner loads. Hull stiffness is not a measured element within the handicap system so a bonus could be possible here compared to existing Js. The existing fleet had generally until now carried a maxi- mum headstay load of 25 tonnes, but to improve stiffness and upwind perfor- mance, a new main longi tudinal structure was designed for an increased headstay load of up to 36 tonnes.
During the design and build we always work closely with the sailmakers as well as the manufacturers of the deck equipment, mast and rigging to optimise weights, deck layout and sail handling. With the consid- erably higher loads we are now targeting, as well as the constant development (ie increase) in line speeds, we require the most out of the winches and hydraulic sys- tem. This becomes most evident in a gybe- set manoeuvre, when most of the deck winches need to work simultaneously at different speeds and loads, asking different flows and pressures from the hydraulics. Today’s J-Class boats all also now boast full carbon spars and carbon rigging. This, combined with the latest more rigid sail materials and sheets and halyards, means that with little stretch available deforma- tions are so slight that the dynamic loads have increased substantially throughout the sail-management systems. Much research has also been done by our team, together with Southern Spars and North Sails, on the optimal stiffness of the mast and rigging, and the interactions with both sail shapes and rig weight and CoG. Under the current J-Class rules the boats sail against each other using a handicap determined by the actual boat parameters and a measured stability. For this reason we remain involved in all of our projects after launch to optimise each design to its handicap to keep a little edge on the com- petition… Differences in weight, stability and sail areas are carefully calculated
28 SEAHORSE
within our CFD software to compare actual difference with the calculated differ- ence in handicap.
Of course, the new Js are not only designed for racing but also for cruising, and emphasis has necessarily been given to optimise deck layouts for both. With her unusual double cockpit layout, Lion- heart’s large centre cockpit is used for sail
storage during racing, while in cruising mode it accommodates a large dining table for eight to 10 guests.
Rather crucial on the Js with their large fractional rigs and inline spreaders are the runners, and when racing these can be operated conveniently and without dis- traction while standing in the smaller aft cockpit. In cruising mode this aft cockpit
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