This report contains the results of resistance tests on a systematic series of fast round-bilged displacement type model hulls, and formed part of a programme of research into this type of vessel undertaken by Ship Division of the National Physical Laboratory.

There is an obvious lack of design data available for this class of vessel. Most of that which is available is empirical, for example Barnaby (ref. l), Marwood and Silverleaf (ref .2), and only Taylor (ref .3) has presented comprehensive data based on a systematic model series. Unfortunately, this standard series is based on a normal ship form, which is not really intended for the higher speeds associated with round-bilge craft. Similar work by Yeh (ref.4) and Nordström (ref.5), though based on suitable hull forms, is limited in scope. The desire to provide data sufficiently comprehensive and extensive to cover the range of length-displacement ratio (M), encountered in this type of vessel, prompted the decision to carry out the work described here. Examples of vessels covered by these data in this report are patrol vessels, launches, work and river boats and vessels approaching .destroyer form such as corvettes and frigates.