SHIP MOTIONS 



201 



Length bet' Perpendiculars — 128.00 m 



Breadth moulded 11. 50m 



Depth moulded 10.40 m 



Top of ShelU 



Poop Deck Side Line 



Upper Deck Side Line 

 2nd Deck Side 



Designed Full Load Condition, Draught moulded 8.25 m 



Displacement (inc.skln)-13,870 tons 



Black Coefficient 0.728 



Prismatic Coefficient — 0.738 



Midship Coefficient 0.987 



Long. Position of C.of Buo^anc^ 

 0.42 m Forword of Midship 



ow Chock 



Shell 



Top of She! 



2a6 



Fig. 42 Body plan, stem and stern contour of the Nissei Maru (from Experiment Tank Committee of Japan, 1954) 



Upper PeckSide Line 

 2nd Deck Side Line 



10 



I 2 



50 100 



Wave Length \.(m) 



150 



200 



Fig. 43 Relation between wave height and wave length ob- 

 served (from Experiment Tank Committee of Japan, 1954) 



tlie irregularity of the .sea and its effects. The observers 

 on the SS Nissei Maru, however, stressed this aspect 

 more than it has been done in the past and also gave 

 various graphs and iHscussions comparing ship behavior 

 in irregular sea waves with model beha\-ior in regular 

 t owing-tank waves. However, they had no practical 

 means of measuring sea irregularity and establishing 

 the quantitati\-e relatifniship between irregular wa\-es 

 and ship motions, which was done by C'artwright (1957, 

 1958) and Cartwright and Rydill (1957). 



5.16 Additional data oq sea voyages. Rexiews of 

 observations at sea, particularly of ship stresses can be 

 found in the work of Koop (19o2) and in Admiralty 

 Ship Welding Committee Report No. 8 (I95o). 



Williams (1952) gave data on the distribution of roll- 

 ing amplitudes and periods measured at sea on British 

 cruisers. He pointed out that, on the average, rolling 



100 ISO 



Wave Length \(m) 



250 



Fig. 44 Relation between wave period and wave length ob- 

 served (from Experiment Tank Committee of Japan, 1954) 



records conform to Rayleigh's distribution law although 

 indi\-idual records vary. In the appendix to his paper, 

 Williams gave the derivation-' of Rayleigh's law for the 

 frequency distribution of wave heights of randomly 

 varying sea waves. He also ga\'e some data on damping 

 in roll as detei'inined by the artificial rolling of ships. 



Captain Patterson (1955) described many cases of ship 

 behavior and handling during severe storm conditions. 



Cartwright (1957, 1958) and Cartwright and Rydill 

 (1957) opened a new era in the field of c|uantita- 

 ti^'e ship measiu'ements at sea. For the first time a ship- 

 l)orne wave-height recorder was used simultaneously 

 with the accelerometers and gyros recording ship motions. 



AVarnsinck and St. Denis (1957) described comparative 



-' The deriv:iticiiifi were maiU- l)v X. F. Barljer. 



