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Stability has to be a "built in" attribute if a water-speed contender is to be both safe and successful. The craft's shape and weight distribution must be very carefully worked out long in advance of construction. To help define and then refine the shape of the Quicksilver craft, the team has undertaken extensive testing of scale models in windtunnels and on water, combined with computer-based studies. We have designed a boat that is going to travel at aircraft speeds. It is still undeniably a boat, but the forces acting upon Quicksilver at extremely high speeds will, to a very large extent, be the same forces an aircraft has to cope with – aerodynamic forces generated by the airflow interacting with the craft. Once Quicksilver has accelerated up onto her planing surfaces, she will have very little contact with the water. She will be surrounded almost entirely by air. The behaviour of the air as it interacts with our boat therefore has a far greater influence than is the case with slower, more conventional boats – more especially since Quicksilver will be the fastest boat ever built, and the faster the speed, the greater the aerodynamic influence. When designing any machine that is going to travel at high speed – whether it is a road-going car, a racing car, a truck, a locomotive, a powerboat, or an out-and-out speed machine like Quicksilver – it is safer, more economical and plain engineering good-sense to test the concept in a wind-tunnel before committing to building the real thing. The concept’s shape is a crucial factor governing its performance, but so too is its weight and weight-distribution. Stability, speed, safety; all derive from the combination of those three influencing factors. Wind-tunnel testing tends to be a process of trial and error, but guided by the established principles of aerodynamics. And there is always something new to learn. The test data Quicksilver’s designers have been particuarly interested in pertain to lift (you don’t want to the boat to become airborne or to run too lightly on the water), drag (because poor streamlining limits the craft’s acceleration and ultimate speed), and pitching moment (that’s any tendency – to be avoided at all costs – for the boat to flip over backwards). Quicksilver’s wind-tunnel testing has involved mounting scale models representing a variety of different craft concepts in two facilities at opposite ends of England. Initially, our wind-tunnel testing was undertaken at the University of Southampton and the models ranged in size from one-eighth-scale up to one-fifth-scale. The wind-tunnel used in many of those tests had a "moving ground" to simulate the presence of the water's surface passing beneath the craft. More recently, Quicksilver's wind-tunnel testing has taken place at the University of Salford, using a one-tenth-scale model kindly manufactured for the team by the Innov8es company. In the case of both the University of Southampton and the University of Salford, our research has been a collaborative effort involving undergraduates working side-by-side with Quicksilver’s designers. The craft being built today is the result of a total of almost 50 days of research conducted in the two wind-tunnels. Various concepts were either abandoned or refined after much experimentation. Knowledge was gained that is standing us in good stead. There were many, many, false dawns. Eventually we arrived at a design we felt entirely happy with. Particular praise is due to our chief aerodynamicist, Mike Green, for guiding the conceptual design project to a successful conclusion. Mike was formerly the chief aerodynamicist at British Aerospace's Woodford, Cheshire, facility. He joined the Quicksilver team in 2005. The team is also grateful to Dr Thurai Rahulan of Salford University for his on-going role in our aerodynamic research programme, and acknowledges the enormous contribution made at an earlier stage by the late Ken Burgin of the University of Southampton. Wind Tunnel Testing at Salford - 1 Wind Tunnel Testing at Salford - 2 Just as Quicksilver's aerodynamic performance has been refined by windtunnel tests, so the hydrodynamic performance has been refined by water-tank towing tests and testing of free-running models operated by radio control. Not only the current shape, but other completely different shapes, were tested over the years. For example, an intensive series of waterborne tests of a reverse four-pointer concept (pictured above on a demonstration run in the towing-tank at the University of Southampton) was conducted with a one-eighth-scale model in the quarter-mile-long towing tank at the Centre for Marine Technology at Haslar, near Portsmouth. For more details of model testing involving earlier Quicksilver craft concepts, please visit the Earlier concepts page. |