Section 28.535 - Inclining test(a) Except as provided in paragraphs (b) and (c) of this section, each vessel for which the lightweight displacement and centers of gravity must be determined in order to do the calculations required in this subpart must have an inclining test performed.(b) A deadweight survey may be substituted for the inclining test, if there is a record of an inclining test of a sister vessel. A vessel qualifies as a sister vessel if it is built to the same basic drawings and the undocumented weight difference between the two vessels is less than 3 percent of the lightweight displacement of the vessel which was inclined and the location of the longitudinal center of gravity differs less than 1 percent of the vessel's length.(c) A deadweight survey may be substituted for the inclining test, or the inclining test may be dispensed with, if an accurate estimate of the vessel's lightweight characteristics can be made and the precise location of the position of the vessel's vertical center of gravity is not necessary to ensure that the vessel has adequate stability in all probable loading conditions.(d) ASTM F 1321 (incorporated by reference, see § 28.40 ), with the exception of Annexes A and B, may be used as guidance for any inclining test or deadweight survey conducted under this section.CGD 88-079, 56 FR 40393, Aug. 14, 1991, as amended by USCG-1999-5151, 64 FR 67176, Dec. 1, 1999