[Code of Federal Regulations]
[Title 46, Volume 7]
[Revised as of October 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 46CFR170.295]

[Page 109-110]
 
                           TITLE 46--SHIPPING
 
   CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)
 
PART 170--STABILITY REQUIREMENTS FOR ALL INSPECTED VESSELS--Table of Contents
 
                         Subpart I--Free Surface
 
Sec. 170.295  Special consideration for free surface of passive roll stabilization tanks.

    (a) The virtual increase in the vertical center of gravity due to a 
liquid in a roll stabilization tank may be calculated in accordance with 
paragraph (b) of this section if--
    (1) The virtual increase in the vertical center of gravity of the 
vessel is calculated in accordance with Sec. 170.285(a); and
    (2) The slack surface in the roll stabilization tank is reduced 
during vessel motions because of the shape of the tank or the amount of 
liquid in the tank.
    (b) The virtual rise in the vertical center of gravity calculated in 
accordance with Sec. 170.285(a) for a stabilization tank may be reduced 
in accordance with the following equation:

E.F.S.=(K)(F.F.S.)

where--

E.F.S.=the effective free surface.
F.F.S.=the full free surface calculated in accordance with 
Sec. 170.285(a).
K=the reduction factor calculated in accordance with paragraph (c) of 
this section.

    (c) The factor (K) must be calculated as follows:
    (1) Plot (I/d)tan T on Graph 170.295 where--
    (i) (I) is the moment of inertia of the free surface in the roll 
tank;
    (ii) (d) is the density of the liquid in the roll tank; and
    (iii) (T) is the angle of heel.
    (2) Plot the moments of transference of the liquid in the roll tank 
on Graph 170.295.
    (3) Construct a line A on Graph 170.295 so that the area under line 
A between T = 0 and the angle at which the deck edge is immersed or 28 
degrees, whichever is smaller, is equal to the area under the curve of 
actual moments of transference between the same angles.
    (4) The factor (K) is calculated by determining the ratio of the 
ordinate of line A to the ordinate of the curve of (I/d)tan T, both 
measured at the angle at which the deck edge is immersed or 28 degrees, 
whichever is smaller.

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