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1859 was accomplished when he was in his late teens. He was probably without schooling in naval architecture and therefore had not been taught that powerboats could go no faster than sailboats. He built and proved his dream before he knew it wasnt supposed to be possible. Analogous to the big bang? theory with regard to the universe, I take ornycrofts steam launch Ariel as the beginning of time? for measuring evolving technology for developing advanced performance of round-bilge and hard-chine monohull vessels. As a discriminator of time periods, I use the type of propulsion machinery to address related technologies evolving during each period. is seems logical, as advanced craft have gen- erally been developed around best available engines at the time of a project. Reciprocating steam engines From Ariel in 1863 to steam yacht Arrow in 1902, the high-est speeds of steam-powered vessels (launches, yachts, and military) increased from 12+ to 39+ knots, averag- ing seven knots per decade. However, the average rate of absolute speed increase does not indicate a smooth rate of technology development with respect to Froude number. Miranda s F nL = 0.82 in 1871 was not equaled or exceeded until 1890 when steam yacht Norwood , designed and constructed by American Charles Mosher, sea trialed at F nL = 0.98. Before 1890, most of the examples of speed gains resulted from a combination of increases in both hull length and installed propulsive power. However, the fastest dimensionless speed reciprocating steam powered vessel, FnL = 1.15, was achieved by the American designed and built steam launch Ellide in 1897. Key craft having performance increases over time are shown, along with important builders, in Figures 1 and 2. Lets look at technology advances from 1863 to 1902. Reciprocating steam engine technology expanded dra- matically during this perio d, advancing from simple engines to compounding two, three, and then four cylin- ders. Each cylinder of compound engines had di erent diameters, constant stroke (thus different swept vol- umes) and all pistons were connected to a common rpm crankshaft. High-pressure steam from a boiler entered the smallest diameter cylinder, exhausted into the next larger diameter, and so on, until nally exhausting into the atmosphere. Compound double and triple expansion engines were reasonably reliable. Quadruple expansion engines were only successfully developed by a few man- ufacturers as it was di cult to avoid water vice steam entering the fourth cylinder. Matching boiler steam pressure and volume ow rate with engine characteristics with a propeller directly cou- pled by a shaft to the crankshaft was often a trial-and-error process. e highest F nLvessel, Ellide, had a quadruple expansion engine. e second highest Froude number vessel, at F nL = 1.03, was Turbinia , which had steam tur- bine power, and which will be examined separately. Ferdinand Schichau, a German shipbuilder in Elbing, Prussia manufactured in 1884 the rst triple expansion reciprocating steam engines of the shipyards design on the European continent for German navy S1 torpedo boats. In 1896, the HAI LUNG class of torpedo boats were designed and built by Schichau for China and were the www.sname.org/sname/mt April 2013 Figure 1: Build dates of signi? cant vessels and record speeds