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The authors wish to thank the discussers for their comments and questions. Some questions were raised because we could not include all specific details and explanations concerning the layout of the Series '89 due to space limitations. We are grateful to Dr. Savitsky for his friendly introduction to our subject.

A mathematical representation of calm-water resistance for contemporary planing hull forms based on the USCG and TUNS Series is presented. Regression analysis and artificial neural network (ANN) techniques are used to establish, respectively, Simple and Complex mathematical models. For the Simple model, resistance is the dependent variable (actually R/∆ for standard displacement of ∆ = 100000 lb), while the Froude number based on volume (F nV ) and slenderness ration (L/V 1/3 ) are the independent variables. In addition to these, Complex model's independent variables are the length beam ratio (L/B), the position of longitudinal centre of gravity (LCG/L) and the deadrise angle (β). The speed range corresponding to F nV values between 0.6 and 3.5 is analyzed. The Simple model can be used in the concept design phases, while the Complex one might be used for various numerical towing tank performance predictions duringall design phases, as appropriate.

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Contemporary propulsors in tubes (waterjets, nozzles, side thrusters) are relatively cumbersome and definitely stem from simpler unshrouded installations. For shrouded installations, tip-driving is almost a natural solution. Although a novel concept, Mechanical Tip-Driven Propulsor (MTDP) is technically and economically feasible. Some noteworthy features of tip-driven propulsors are compact design, possibly higher efficiency, shrouded propeller, contra-rotation in the nozzle for steerable installations, etc. The TDP operates under undisturbed hydrodynamic conditions resulting in higher efficiency. The complete propeller disc is exploited for propulsion since the propeller shaft, the boss, the thrust column, etc. do not exist. Anticipated problems are sealing of the circular chamber and the gearbox. It is expected, however, that the gain in efficiency is to be larger than are the sealing frictional losses. A number of possible applications of TD concept in marine vessels are given, as for example contra-rotating lip-driven rudder-propeller, lip-driven waterjet, etc.

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Mathematical representations for the resistance, trim, and wetted length of the Experimental Model Basin Series 50 have been developed using conventional regression analysis techniques as well as artificial neural networks. Series 50 is a standard series of 20 V-bottomed motor boats tested in 1941. These hulls could be representative of today's semidisplacement hulls. Recently, the series has been reanalyzed and published using contemporary planing coefficients, enabling resistance prediction in design stages. In the present study, mathematical representations are developed for the Series 50 as an alternative to using charts or data tables. Two methods are used, regression analysis and artificial neural networks. This study provides a useful resistance prediction method for designers and an opportunity to compare and contrast regression analysis and artificial neural networks applied to standard series. The main finding of the study is that both techniques were capable of developing stable and accurate models. A detailed quantification of the differences between methods is provided.