46 CFR §171.065

1. (a)Except as provided in paragraphs (c) and (f) of this section, the separation between main transverse watertight bulkheads on a vessel, other than one described in paragraph (b) of this section, must not exceed—
2. (b)The factor of subdivision used to determine compliance with paragraph (a) of this section must be the smaller of 0.5 or the value determined from Table 171.065(a) if—
   1. (1)The vessel is 430 feet (131 meters) or more in LBP; and
   2. (2)The greater of the values of Y as determined by the following equations equals or exceeds the value of X in Table 171.065(b):
3. (c)The distance A in Figure 171.065 between main transverse watertight bulkheads may exceed the maximum allowed by paragraphs (a) or (b) of this section if each of the distances B and C between adjacent main transverse watertight bulkheads in Figure 171.065 does not exceed the smaller of the following:
   1. (1)The floodable length.
   2. (2)Twice the separation allowed by paragraphs (a) or (b) of this section.
4. (d)In each vessel 330 feet (100 meters) or more in LBP, one of the main transverse watertight bulkheads aft of the collision bulkhead must be located at a distance from the forward perpendicular that is not greater than the maximum separation allowed by paragraph (a) or (b) of this section.
5. (e)The minimum separation between two adjacent main transverse watertight bulkheads must be at least 10 feet (3.05 meters) plus 3 percent of the LBP of the vessel, or 35 feet (10.7 meters), whichever is less.
6. (f)The maximum separation of bulkheads allowed by paragraphs (a) or (b) of this section may be increased by the amount allowed in paragraph (g) of this section if—
   1. (1)The space between two adjacent main transverse watertight bulkheads contains internal watertight volume; and
   2. (2)After the assumed side damage specified in paragraph (h) of this section is applied, the internal watertight volume will not be flooded.
7. (g)For the purpose of paragraph (f) of this section, the allowable increase in separation is as follows:
8. (h)The assumed extents of side damage are as follows:
   1. (1)The longitudinal extent of damage must be assumed to extend over a length equal to the minimum spacing of bulkheads specified in paragraph (e) of this section.
   2. (2)The transverse extent of damage must be assumed to penetrate a distance from the shell plating equal to one-fifth the maximum beam of the vessel and at right angles to the centerline at the level of the deepest subdivision load line.
   3. (3)The vertical extent of damage must be assumed to extend vertically from the baseline to the margin line.
      1. (i)The maximum separation between the following bulkheads must not exceed the maximum separation between main transverse watertight bulkheads:
         1. (1)The collision bulkhead and the first main transverse watertight bulkhead aft of the collision bulkhead; and
         2. (2)The last main transverse watertight bulkhead and the aftermost point on the bulkhead deck.
9. (j)The minimum separation between the following bulkheads must not be less than the minimum separation between main transverse watertight bulkheads:
   1. (1)The collision bulkhead and the first main transverse watertight bulkhead aft of the collision bulkhead; and
   2. (2)The last main transverse watertight bulkhead and the aftermost point on the bulkhead deck.