SHIP MOTIONS 



199 



-o 



o 



4 G 8 10 



Periods of Encounter-Seconds 



IZ 



Fig. 39 Relation between pitching period and period of en- 

 counter (from Admiralty Ship Welding Committee, 195 3) 



were summarized in tables. An abstract from the.se 

 tables is given in Table 9 for five observation periods. 

 Observations 18 and 77 correspond to Figs. 45 and 46. 



Fig. 45 and observation No. 18 in Table 9 correspond 

 to a mild quartering sea. They disclose an interesting 



40 



30 



^ 20 



10 



Average Natural Rolling Period 

 in Ballast -9.5 Seconds 



■Westbound Crossings 

 C In Ballast) 



Average Notural Rolling Period 

 when Loaded-10.8 Seconds 



^^^^Eastbound Crossings 

 . (Loaded) 



\ 

 \ 



\ 





9 10 II \Z 13 14 



Periodic Time of Roll in Seconds 



Fig. 40 Distribution of rolling periods over a typical period of 

 one year. Note: Values on which these curves are based are 

 taken from six crossings in each direction. There are inevitable 

 slight differences in GM between crossings, which will result in 

 some variations in mean of natural period of roll for individual 

 crossings (from Admiralty Ship Welding C^ommittee, 1953) 



Table 9 Data on the Voyage of the SS Nissei Maru 



(Abstracted from Experiment Tank Committee of Japan, 1954) 



Observation number 18 09 74 77 79 



1 )isplac-ement, tons 6440 .— 13,450 



Course, <legrees 62 232 265 250 270 



Wind absolute, Beaufort W5 S/EG \\7X7 W7 WN\V5 



Wind al>solute, direction deg, . 207 164 2S() 270 290 



Wind absolute, velocity m/s. . 12.0 12 4 15 2 18 1 10 8 



Wind relative direction, deg. . P/ISO P50 SI2 S20 S20 



Wind relative velocitv, m/s. . . 0.5 15 19 5 21 15 



Wave length, m 30 55 100 1.50 120 



Wave height, m 1.5 3 5 (i 5 



Wave direction, deg P/140 P40 S5 S20 SIO 



Ship speed, knots 13.47 9 8 73 0.10 8.73 



HPM 92.3 89.7 87.1 78.8 85 5 



SHP 2379 3009 3389 2801 .3028 



Torque (mean), tm 18.50 24 52 27 SO 20.02 25.37 



Torque (fluctuation ampl), 



percent 39 .34 27 45 40 



Pitching (maximimi), deg — 3.5 4.8 0.0 5.2 



Pitching (mean), deg — 1.7 3.1 3.0 3.4 



Pitching period, sec. — 7.5 8.2 8.0 8.0 



Rolling (maximum), deg — 2.5 0.5 10.1 8.3 



Rolling mean, deg — 1.3 2.8 01 57 



Rolling period, sec — 12.8 12.9 12.9 12 



'I'awing (maximum), deg 5.0 2.0 4.9 5.4 3.8 



^'awing (mean), deg 2.2 — — — — 



Rawing period, sec — 0.2 9 5 9 10 



Helm angle (maximum), deg. . 14.0 17.5 17 5 10 4 9 



Stress" (ma.ximumi, kg/cm2... 113.5 265.0 303 410 41(iO 



Stress (mean), kg/cm2 74.4 130.0 144 182.0 100 



"» Near the edge of the deck, .)Ust .aft of Xo. 3 cargo hatcli and in front of (he ^ 

 ture. 



270 



W/N6 



283 



13 1 



SIO 



10 



140 



5 



S5 



5 61 



69.0 



2042 



21.20 



55 



8.5 



2.4 



0.7 



5 



1 8 



10 



18. I 

 378.0 

 100 5 



U])erstruc- 



