up for its small area compared to a hull forebody. At high planing speeds where the 

 ski wake clears the fuselage, the water resistance can approach that of the planing 

 surface alone, depending primarily on wetted aspect ratio and angle of attack. 



Spray. — Large amounts of spray are generated by a small ski gear, particularly 

 during emergence when the angle of attack is high and the ski nose is breaking the 

 surface. The spray remains severe at planing speeds because of the high hydrodynamic 

 loading. Most of this spray is relatively harmless, but makes a high degree of water- 

 proofing and corrosion resistance important in the engineering design. 



Rough-water qualities. — Highly loaded skis increase the effective stroke during 

 water impacts to a degree dependent on their size and shape, and thus offer a further 

 fundamental improvement in rough-water capabilities. This quality has been observed 

 generally in model experiments as well as full-scale operation, and is substantiated by 

 impact theory. Since the loads are localized in the ski struts, additional alleviation for 

 the airplane can be provided by mechanical shock absorbers (ref. [7]), although this 

 elaboration may be fundamentally redundant if the ski size can be made small 

 enough. 



Ski arrangements. — Many ski arrangements are possible for applications of the 

 principle; they may be single or multiple, twin or tandem, retractable into different 

 airplane components, etc., In any event, variations in the system must obviously, as 

 for landplane gears, suit an established operating sequence requiring the minimum 

 of attention and special control from the pilot. 



Additional Hydro-Ski Applications 



The Convair F2Y-1 Sea Dart represents the only literal application so far of 

 the bold hydro-ski principle as originally conceived. Several additional concepts have, 

 however, appeared from military attempts to evaluate the usefulness of the idea, which 

 are of potential importance. These concepts are summarized in Figure 4. 



PANTOBASE 

 GEAR 



A. 



/ / ; / / r >'/ s / 



WATER 



SOFT SURFACES HARD SURFACES 



HULL 

 AUXILIARY 



DITCHING 

 AID 



LAND -WATER 

 GEAR 



7;/////'-' 



WATER 



RAMP OR BEACH 



SERVICE AREA 



Figure 4. Additional hydro-ski applications. 



188 



