V. New Configuration and Concepts 



High-Speed Hulls 



The classic hydrodynamic solution for a large water-based airplane remains the 

 flying-boat hull which combines the functions of the fuselage, floatation, and landing 

 gear. Such a hull for a high-speed jet-propelled configuration reflecting several features 

 resulting from post-war research and development is shown in Figure 2. 



BOTTOM VIEW 



FRONT VIEW 



L.W.L. 



PROFILE 



Figure 2. Typical high-speed hull. 



Overall proportions. — One of the basic contributions has been an emancipation 

 from arbitrary beam formulas, provided the hydrodynamic lengths are selected to suit. 

 When the beam is reduced to reduce frontal area, the required lengths, particularly 

 the forebody length, increase at a slower rate, resulting in a smaller bottom area 

 without sacrifice of essential hydrodynamic qualities (ref. [1, 2, and 3]). The higher 

 beam loading results in lower wetted aspect ratios and more intense side spray at the 

 hump and planing speeds (ref. [4]); on the other hand, it provides a significant allevi- 

 ation in water impact loads and motions (refs. [2 and 5]). This beneficial process can 

 be carried to a practical limit from the construction point of view and embraces 

 hydrodynamic length-beam ratios entirely compatible with the high body fineness 

 ratios and low frontal areas mandatory for low drag at supersonic speeds. 



Forebody. — With a hull of the type shown, the long streamlined forebody is 

 hydrodynamically necessary for buoyance, cleanness of running, and low water resist- 

 ance at pre-hump speeds. The relatively high angles of dead rise favorable for absorp- 

 tion of impacts at high water speeds are also advantageous with regard to low-speed 

 spray (ref. [6]). The heavy main spray can be controlled to some extent by horizontal 

 chine flare, or even vertical chine strips or "spray dams," but the close coupling of 

 high-speed configurations still makes high wing and tail positions desirable for sea- 

 worthiness. 



Step. — The trend in step design as shown is the use of a highly tapered plan 

 form with some form of step fairing. These features minimize the aerodynamic and 

 structural discontinuities and appear hydrodynamically acceptable if not carried too 

 far. The tapered plan form tends to reduce impact loads (ref. [7]) and to improve 

 the landing stability with shallow step depths. 



Afterbody. — The long clean afterbody and low angle of afterbody keel are 

 almost mandatory in a high-speed hull for buoyancy and fairing purposes. This type 



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