Much research by theory and experiment has been devoted to the improvement 

 of the operational qualities of ships. Emphasis is strongly veering towards the develop- 

 ment of the best shape of hull and distribution of load for seagoing conditions rather 

 than for calm water, to which much attention has been devoted in the past. This is 

 evident from the new facilities being constructed in America and Great Britain and 

 that recently completed in the Netherlands for realistic investigations of seaworthiness 

 and ship motion. There is also a rapidly expanding interest in cavitation and addi- 

 tional facilities for investigating this phenomenon are being provided in various coun- 

 tries. The boundaries of research are being thus extended in order that ships may 

 clear the hydrodynamic barriers as far as possible. We may look forward to faster, 

 steadier, handier and more economical ships, although advance will continue to be 

 circumscribed by the physical limits imposed by the density and viscosity of water and 

 of air and of the vapour tension, gas content and surface tension of water. 



Much fuel is squandered by ships in overcoming the skin friction resistance 

 of the hull and to a smaller extent the propeller. There has been an improvement in 

 this respect of about 10 per cent following the advent of welded hulls. If a ship could 

 be built as smooth say as bonded plastic asbestos, research informs us that the frictional 

 resistance of a clean hull might be further reduced by say 10 per cent. Luxurious 

 animal and vegetable life thrives on a ship's hull to such an extent that the frictional 

 resistance may be increased by 25 per cent when six months out of dock. This is 

 about one half the increase that obtained some years ago, which is one indication of 

 the achievement of research. Thus the door to the barrier of viscosity is being pushed 

 slowly open. 



The inventor seeks to break through by clothing the ship with air but is 

 defeated by the excessive power of the necessary air compressors. Laminar flow and 

 boundary layer control offer entrancing theoretical prospects but formidable problems 

 are presented including a revolution in shipyard practice to obtain the necessary 

 smoothness of hull finish and the annihilation of the barnacle and its fellow travellers. 



Rough weather can severely limit the overall operational performance of a 

 ship due to the consequential oscillations in the six degrees of freedom, shipping heav- 

 ing seas over the bow and exposed operational positions, and by reducing speed. 



It may be necessary to ease the speed below that obtainable from the propelling 

 machinery to reduce the ship motion and prevent structural damage. Generally con- 

 ditions are most severe in seas of a length somewhat greater than that of the ship, 

 for example, studies on a model of a carrier about 700 feet long indicated that the 

 speed would be a minimum in steep seas about 800 to 900 feet long and about 40 

 per cent of the full speed. Ninety-five per cent of the full speed could be obtained in 

 waves about half the critical length. By and large the severity of the motion changes 

 similarly with the length of wave. Detailed investigation indicated that the probability 

 of the carrier meeting conditions limiting flying operations was on a conservative basis 

 18.5 per cent in the North Atlantic and 12 per cent as an average of all the oceans of 

 the world. 



If the ship were twice the size, namely 1400 feet length the probability would 

 be expected to be about halved, although this has not been examined in detail. Thus 

 a definite if not very striking gain in sea-keeping qualities would be expected if the 

 size of ship could be increased well above the present maximum length of about 1000 

 feet. 



Ships generally are much smaller than the few giants of about 1000 feet length. 

 The probability of objectionable motion is greatly enhanced as critical seas are more 

 frequently encountered. Model experiments have shown that the pitch and heave 

 amplitudes can be reduced by a worthwhile amount by suitable shape of hull ('V 

 sections forward and flat sections aft are one example) and by about 50 per cent if 

 longish passive fins are fitted. The damping varied with speed of model and size of 

 wave. The relative gain was less in short waves but the motion was then small. Thus 

 there could be a considerable advance if the fin device were considered practicable, 



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