Series 50 is the largest U.S. planing hull series. Originally developed for semi-planing PT boat type hulls, the tests were conducted in 1940-1941 and consisted of twenty 1m long models tested at nine loading conditions each and a range of speeds for a total of over 2000 test runs. The volumetric Froude numbers tested ranged from 1 to 6. The parent hull of the series has warp, rocker in the buttock lines and a tapered stern, features that are undesirable in very high speed craft, but are often necessary in the design of semi-planing hulls such as motor yachts. Analysis of all of the series data showed that the flow was not fully turbulent on all of the runs, especially conditions with wide beam and short wetted lengths. A thorough re-analysis of the data was undertaken and for runs with suspected transitional flow, the lift, wetted length and trim angle were used to determine resistance, using a modification of methods employed for prismatic planing hulls. Plots are developed showing mean wetted length and residuary resistance to weight ratio as a function of Froude number, allowing the data to be rapidly expanded to any scale ratio. Corrections for aerodynamic resistance, trim flaps and appendages are discussed, and example calculations are provided.

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