Shifter
The National 12 class in the UK has been the breeding ground for several particularly creative and free-thinking modern yacht designers including Bol d’Or champion designer Jo Richards and DSS inventor Hugh Welbourn. With few constraints and hydro and aerodynamic efficiency paramount, this non-trapeze class has seen imaginative solutions to very diverse questions. Now it is the setting for about as big an efficiency challenge as you could ask for… Designer Gavin Willis talks to current national champion Graham Camm
National 12 evolution since 2009 – and the concept of shape shifting The National 12 is a well-established UK development dinghy class. The boats have a light hull, just two sails and a crew of two. The first 12s hit the water in 1936 and designs have continued to evolve ever since. Modern boats are carbon-foam sandwich while many beautiful wooden vintage boats are still sailing, particularly on inland waters where a well-sailed older design can still be competitive in the right conditions. Thirty-two years after he appeared in
the class in 1977 with his dramatic Bouncer design (with which he won that year’s championships) a decade ago Jo Richards made waves again in the National 12 class with his remarkable
56 SEAHORSE
Dead Cat Bounce (DCB) design. Jo’s inno- vations in Dead Cat included a trim tab centreboard and a clever fat-head mainsail and jib, but the bigger step forward was probably the use of an unusual amount of hull rocker combined with aggressive use of a large rudder foil adjustable from inside the boat. Jo and his crew Sophie Mackley took the 2009 National 12 title with six wins and discarding a second. Since the 2009 wing revolution the
National 12 class has continued to evolve at a steady pace with competitors trying out different winged rudder configura- tions, until this year when Gavin Willis launched his radical shape-shifting Para- digm 4 design which can now also change hull shape to match the conditions. This
article describes the steady evolution over the past decade and explains the concept behind the Paradigm 4.
Wing development Winged rudders had been tried on National 12s before 2009 but with limited success. What Jo did on the original DCB was make them work in a wide range of wind strengths. The DCB wings were large, positioned close to the surface to intercept the vertical component of the stern wake, swept back and angled up (dihedral) to help with boat handling. Combining with the DCB hull shape that had a low wetted surface area and a noticeable bustle at the stern meant the DCB could be sailed competitively with wings on all the time. The wings have several benefits, includ-
ing reducing drag by flattening the wake and smoothing the transition to planing – there is no more steep hump to get over in order to get on the plane. Being only 12ft long and typically with a
narrow bow, 12s tended to nosedive in a blow and they also had an upper speed where they became quite a handful. With the wings there is no longer a speed ceiling and as you go faster the wings can be eased off, keeping the bow just out of the water. Sailing with wings does, however, require an adjustment to tacking and gybing tech- niques as manoeuvres need to be slower and smoother. Following the successful wing configu- ration on the original DCB there have been
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