SavCtsky^ Roper > and Benen 



speed craft is an essential complement to this fleet. These small 

 craft are called into service to assist in ASW operations ; to patrol 

 in coastal and riverine environments ; and to act in concert with larger 

 naval units. Although ubiquitous in numbers, small craft are not in- 

 dividually a high portion of total naval capability, cost, or personnel. 

 In fact, on an equal cost basis, it appears that more units can be pro- 

 cured which can cover more areas than can larger ships. These fea- 

 tures have made the small, high-speed craft attractive as the princi- 

 pal naval force for many small countries with large coastlines. 



There are basically four different types of small, high-speed 

 craft, i. e. , round-bottom boats, hard-chine planing craft, hydrofoil 

 boats, and various forms of air-supported vehicles. The most nu- 

 merous of these craft is by far the hard-chine planing hull-especially 

 when considering speed-length ratios in excess of approximately 2. 

 where dynamic lifting forces are significant. Because they are equip- 

 ped with large power, lightweight engines, it is not uncommon for 

 planing craft to operate at speed-length ratios in excess of 5. 0. 

 Further, it is also not uncommon for these craft to operate sufficient- 

 ly removed from the coastline so that moderate to high sea states are 

 their normal environment. Thus, the small boat designer is faced 

 with the formidable task of producing craft whose high speed potential 

 is not seriously compromised in rough seas. 



The purpose of the present paper is to describe the hydro- 

 dynamic development of a new planing craft intended for sustained 

 high-speed operation in a seaway. The design philosophy is presented 

 and then implemented to achieve optimum hull form and loading for 

 both smooth and rough water operation of the craft. The resultant hull 

 form is a high length-beam ratio (6. 5), highly loaded (beam loading = 

 0. 75), moderate deadrise ( /3 =20°), double chine configuration 

 which provides good seakeeping, high speed, and large maneuverabi- 

 lity. Extensive model tests were conducted to predict the SHP ; EHP ; 

 seakeeping ; course-keeping stability ; and turning characteristics of 

 the design. The extensiveness of the model test program and data ana- 

 lysis are unique for a planing craft. The present paper presents these 

 results in a form which should be of general interest to designers of 

 high-speed planing hulls. 



POSTULATED PERFORMANCE OBJECTIVES 



The design of any marine craft is based upon specifications 

 which have been prescribed to achieve desired performance objecti- 

 ves. Among the more significant requirements which have a pronounc- 

 ed influence on hull form are : operational speeds ; dimensions and 



420 



