Stability has to be a "built in" attribute if a water-speed contender is to be both safe and successful. The craft's shape, weight and weight-distribution must be very carefully worked long out 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 – namely, aerodynamic forces generated by the fast-moving airflow interacting with the craft. After Quicksilver has accelerated up onto its planing surfaces, most of its hull area will be swathed in fast-flowing 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 as Quicksilver will be the fastest boat ever built, because the faster the speed, the greater the aerodynamic influence.
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 – namely, aerodynamic forces generated by the fast-moving airflow interacting with the craft. After Quicksilver has accelerated up onto its planing surfaces, most of its hull area will be swathed in fast-flowing 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 as Quicksilver will be the fastest boat ever built, because the faster the speed, the greater the aerodynamic influence.
When designing any machine that is going to travel at high speed – whether it be 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 in the long run, and plain engineering good-sense, to test the concept in a windtunnel before committing to building the real thing.
As stated, the concept’s shape is a crucial factor governing its performance, but so too is its weight and its weight-distribution. Stability, speed, safety; all derive from the combination of those three influencing factors.
Windtunnel 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 particularly 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 is any tendency – to be avoided at all costs – for the boat to flip over backwards at high speeds).
Quicksilver’s windtunnel testing has involved testing scale models representing a variety of different craft concepts in two facilities at opposite ends of England. Initially, our windtunnel testing was undertaken at the University of Southampton and the models ranged in size from 1/8th-scale to as large as 1/5th-scale. The windtunnel 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 windtunnel testing has taken place at the University of Salford, using a 1/10th-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 testing conducted in the two windtunnels. 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 aerodynamicist, Mike Green, for guiding the conceptual design process to a successful conclusion, working in close conjunction with our marine architect, Lorne Campbell, who undertook extensive analysis and refinement. Mike was formerly chief aerodynamicist at British Aerospace's Woodford, Cheshire, facility. He joined the Quicksilver team in 2005. Lorne is a world-renowned marine architect who has played a key part in the development of the Quicksilver craft since the days when Ken Norris's early concepts were being assessed, but his contribution became particularly strong from 2005 onwards, when the boat design process underwent a major change of direction.
The team is also grateful to Dr. Thurai Rahulan of Salford University for his ongoing role in our aerodynamic research programme. Acknowledgment is also due for the enormous contribution made at an earlier stage in the project by the late Ken Burgin of the University of Southampton.
To see a clip featuring an interview with Dr. Thurai Rahulan on the Quicksilver windtunnel testing programme at Salford University, click here.
For a clip, featuring an interview with Nigel Macknight, on Salford University's contribution to the Quicksilver project, click here.
To see a clip featuring an interview with Dr. Thurai Rahulan on the Quicksilver windtunnel testing programme at Salford University, click here.
For a clip, featuring an interview with Nigel Macknight, on Salford University's contribution to the Quicksilver project, click here.
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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 many years of development. For example, an intensive series of waterborne tests of a reverse four-pointer concept was conducted with a 1/8th-scale model in the quarter-mile-long towing tank at the Centre for Marine Technology at Haslar, near Portsmouth.
For more information on model testing involving earlier Quicksilver craft concepts, please visit the Earlier concepts page.