HIGH PERFORMANCE MARINE VESSELS
Liang Yun, Alan Bliault
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Speed is not simply about velocity in air or water but should be considered in context with its purpose and the tools available. Until recently in historical terms, the motive power available for travel over the water was manpower itself or wind. Over many centuries sailing vessels have been refined so that they could harness more of its power efficiently, and reach higher into an oncoming wind so as to perform a more direct route to the objective. The wind is not available to order nevertheless, and so "speed" achieved is not constant. The invention of reciprocating engines, initially steam driven, made a step change for maritime transport, just as it did on land a little over two centuries ago. It changed the meaning of speed over water, since not only could a vessel be designed to travel directly to its destination, but also could transport much greater payloads than possible previously, and could deliver independent of the weather environment. In the first century of powered marine craft, speeds increased from around 20 knots to about double that. At such speed, there are challenges even for large craft due to rapid increase of drag on the hull if a boat continues to try to push its way through. The propeller driving such a vessel also loses efficiency due to a phenomenon known as cavitation unless specially designed to harness it. In the early part of the twentieth century, pioneering engineers conquered both problems and developed planing craft that could travel much faster by skimming over the water surface. The racing fraternity that grew in this period took things to the limit and produced craft that were in danger of flying if a stray gust of wind should hit...
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