One of the last bow rudders for a while at least (left). Now with the addition of a DSS foil Wild Joe remains one of the last CBTF survivors in original configuration. Even today the hydrodynamics of CBTF remain excellent but the mechanics were heavy and prone to friction and linkage play – plus optimising steering ratios between fore and aft rudders for different sailing conditions was a nightmare. But Tom Blackaller’s twin-rudder 12 Metre USA showed what Dennis Conner recalls as ‘scary’ bursts of speed in Fremantle in 1987 so maybe the CBTF story is not over yet. With good design and engineering the DSS system (above) takes up surprisingly little internal volume – though slender this 60-footer does have reasonable freeboard
terms of displacement and VCG change. (An impressive piece of work by the way). The largest weight saving came by
replacing batteries. Typical of many older yachts, Wild Joe carried a large 24V lead battery bank to power the yacht systems. This battery had to be replaced, firstly to reclaim the weight, and secondly to increase the maximum power available. New mod- ern batteries maintained the overall capac- ity at around 9kW/h but, more importantly, saved 110kg and increased the usable power by some 50 per cent. The yacht could now day race under battery power alone with no charging needed once off the dock. The DSS case itself needed to be installed
pretty much where the hydraulic tank and pump set had been, meaning that these were next in focus. To generate high flow for the original canting-keel system Wild Joe had been fitted with three pump sets, with total hydraulic power around 10kW. Each one of these pump sets weighed in around 20kg,
44 SEAHORSE
and when working hard pushed a lot of heat into the yacht. We took an early decision to integrate
the new hydraulic tank into a side berth and upgraded the pump system to a variable- speed AC motor. The advantages are many – reduced weight (another 40kg back in the bank), reduced heat output and super-com- pact size. As we now had smaller modular components for the keel system, installation was further optimised, shortening hose runs to the minimum and relocating the oil tank and pump much closer to the keel rams. More weight saved. Removal of any
redundant equipment, and careful place- ment of smaller yacht systems rounded out the weight saving. We now had some weight to spend on DSS controls. The DSS foil in Wild Joe is a transverse
system. Maverick, the Infiniti 46R, used twin scimitar-shaped foils, each with manual line drivers to retract and extend the foils. The line-driven system was simple,
reliable and light. Choosing a plain bearing line pull system for Wild Joe also made sense and kept the transverse system simple. VoltSport developed a custom line driver
for the Wild Joe foil, capable of 520kg line pull at up to 25m/min. This system includes another smaller AC motor, complete with speed control, compact inline gearbox and custom large-diameter line drive pulley. All this came in under the 20kg budget, and so the neutral overall budget was achieved. The yacht’s DSS control is push-button
at the helm. Five positions are possible – full extension, flush with hull, and centred (for docking). The Wild Joe DSS foil also fea- tures integrated magnetic target locations with position sensors within the foil case. The PLC controlling the DSS also modu- lates speed of travel to prevent overrunning the target – you cannot stop such a large foil instantly – and so we predict-position and soft-stop the foil on the target location. Repeatability is excellent, and feedback of
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