Section 42.20-50 - Effective length of superstructure(a) Except as provided for in paragraph (b) of this section the effective length (E) of an enclosed superstructure of standard height shall be its length.(b) In all cases where an enclosed superstructure of standard height is set in from the sides of the vessel as permitted in § 42.13-15(j) , the effective length shall be the length modified by the ratio of b/Bs,where:
"b" is the breadth of the superstructure at the middle of its length;
"Bs" is the breadth of the vessel at the middle of the length of the superstructure.
(1) Where a superstructure is set in for a part of its length, this modification shall be applied only to the set in part.(c) Where the height of an enclosed superstructure is less than the standard height, the effective length shall be its length reduced in the ratio of the actual height to the standard height. Where the height exceeds the standard, no increase shall be made to the effective length of the superstructure.(d) The effective length of a raised quarter deck if fitted with an intact front bulkhead, shall be its length up to a maximum of 0.6L. Where the bulkhead is not intact, the raised quarter deck shall be treated as a poop of less than standard height.(e) Superstructures which are not enclosed shall have no effective length.CGFR 68-60, 33 FR 10065, July 12, 1968