Chapter 3-STABILITY AND BUOYANCY 





o 

 z 



H 

 X 

 O 



CA 



CURVE OF GGiXsine 



GGi=2.1 



10 20 30 40 50 60 70 



ANGLE OF HEEL IN DEGREES 



80 90 



147.36 



a 

 b 



Z 



►H 



s 



< 



O 



Z 



P 



S 



o 



Figure 3-20.— Sine curve superimposed on original stability curve. 



GG X sin d 



CURVE OF LOSS OF RIGHTING ARM 



GGi 



ANGLE OF HEEL IN DEGREES 



147.37 



Figure 3-21. — Curve of static stability as corrected for loss of 

 stability due to a vertical weight shift. 



remain at this angle and in a seaway it will 

 roll about this angle of permanent list. This 

 shift of G can be computed from the formula 



^iS 



wd 

 W 



where 



^1^2 



athwartship shift of G, in feet 



w = weight moved over, in tons 

 d = distance w moved, in feet 

 w= displacement of ship, in tons 



Going back to our original problem, let us 

 further assume that ship's stores totaling 185 

 tons are shifted from port storerooms to star- 

 board storerooms, a horizontal distance of 

 56 feet. Using the formula: 



^iS 



^ 185 X 56 

 11,500 



0.90 foot 



In figure 3-22 the righting arm has been re- 

 duced from GjZ]^ to G2Z2 by this weight shift. 

 G2Z2 is smaller than GlZi. However, the dis- 

 tance GiT is equal to G1G2 x cos G. Thus, the 



47 



