(a) Each mechanically propelled or non-self propelled vessel other than a pontoon vessel must be shown by design calculations, in each condition of loading and operation, to have a metacentric height (GM) in feet (meters) of not less than the value given by the following equation:
GM = [(W/Δ)(2⁄3)(b)]/(tan(T))
Where -
Δ = displacement of the vessel in long (metric) tons.
W = total weight in long (metric) tons of persons other than required crew, including personal effects of those persons expected to be carried on the vessel.
T = 14 degrees or the angle of heel at which the deck edge is first submerged, whichever is less; and
b = distance in feet (meters) from the centerline of the vessel to the geometric center of the passenger deck on one side of the centerline.
(b) The criteria specified in paragraph (a) of this section are limited in application to the conditions of loading and operation of vessels for which the righting arm (GZ) at the angle (T), calculated after the vessel is permitted to trim free until the trimming moment is zero, is not less than the minimum metacentric height (GM) calculated in paragraph (a) of this section multiplied by sin(T). In conditions not meeting this requirement, the Coast Guard Marine Safety Center requires calculations in addition to those in this section.
(c) A vessel that complies with the requirements for passenger ships contained in the International Code of Intact Stability, 2008 (2008 IS Code) (incorporated by reference, see § 171.012) need not comply with paragraphs (a) or (b) of this section. Vessels complying with the 2008 IS Code must use the Assumed Average Weight per Person obtained according to § 170.090 of this title to be exempt from the other requirements of this section.
[USCG-2007-0030, 75 FR 78085, Dec. 14, 2010]