Davis and Oates 



HISTORICAL NOTE 



The design study and stability analysis reviewed in this paper commenced 

 in October 1960 and has led to the current contract to design and build a 200 ton 

 development prototype ship known as the FHE-400, for the Royal Canadian Navy. 



The initiative came from the Canadian Defence Research Board, following 

 many years of surface piercing foil system development at the Naval Research 

 Establishment, Halifax, Nova Scotia. 



In 1959 N.R.E. published a report which considered the feasibility of a 200 

 ton ship based upon a canard arrangement, of fixed surface piercing foils. 

 N.R.E. recognized the advantages of a canard arrangement in reducing head sea 

 accelerations and improving stability in following seas. In addition, they fore- 

 saw the need to develop a foil design method to provide optimum foil angle of 

 attack range in high sea states. Further, N.R.E. emphasized the value of de- 

 signing a foil system to provide maximum damping in the hullborne mode of op- 

 eration which is particularly important in a military search mode. 



Encouraged by the technical interest of other NATO navies, the Canadian 

 Government agreed with N.R.E, 's contention that a thorough design study should 

 be made and awarded a contract to De Havilland (Canada) in 1960. 



The work statement drawn up by the Defence Research Board in consultation 

 with the R.C.N., laid down the parameters to be considered. These included the 

 development of design methods for foils, response characteristics in random 

 seas and the performance to be achieved. N.R.E. supported the programme with 

 their 3-1/2 ton experimental test craft and an experienced trials team to con- 

 duct sea trials of the foil system developed by De Havilland. The trials con- 

 ducted from 1961 to date have substantiated the predictions made by N.R.E. in 

 1959. 



This paper discusses the design and stability studies and the supporting 

 N.R.E. trials of the RX craft fitted with a representative foil system, 1/4 scale 

 full size. 



DESIGN METHOD 



As there are many factors to be considered in relation to the dynamic sta- 

 bility it is helpful to have a clear picture of the relation of this study to the 

 other design parameters. 



Once the basic role has been decided upon, the required performance, 

 range, load carrying capacity and approximate craft size can be determined; the 

 latter of course, will be dictated to some extent by the sea state in which the 

 craft will have to operate, as the hull will have to clear all but the larger waves. 

 Parametric studies have to be carried out to determine the optimum configura- 

 tion and size to meet the design requirements. These parameters then dictate 

 the foil areas that are necessary to support the craft throughout the required 

 foilborne speed range. Foil section thicknesses and section types are dictated 



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