Section 171.073 - Treatment of stepped and recessed bulkheads in Type II subdivision(a) A main transverse watertight bulkhead may not be stepped unless additional watertight bulkheads are located as shown in Figure 171.067(a) so that the distances A, B, C, and D illustrated in Figure 171.067(a) comply with the following:(1) A and B must not exceed the maximum bulkhead spacing that permits compliance with § 171.070 ; and(2) C and D must not be less than the minimum spacing specified in § 171.070(e) .(b) A main transverse watertight bulkhead may not be recessed unless all parts of the recess are inboard from the shell of the vessel as illustrated in Figure 171.067(c).(c) If a main transverse watertight bulkhead is recessed or stepped, an equivalent plane bulkhead must be used in the calculations required by § 171.070 .