46 CFR §42.20-70

1. (a)The bow height defined as the vertical distance at the forward perpendicular between the waterline corresponding to the assigned summer freeboard and the designed trim and the top of the exposed deck at side shall be not less than:
   1. (1)For vessels below 820 feet in length,
   2. (2)For vessels of 820 feet and above in length,
2. (b)Where the bow height required in paragraph (a) of this section is obtained by sheer, the sheer shall extend for at least 15 percent of the length of the vessel measured from the forward perpendicular. Where it is obtained by fitting a superstructure, such superstructure shall extend from the stem to a point at least 0.07L abaft the forward perpendicular, and it shall comply with the following requirements:
   1. (1)For vessels not over 328 feet in length it shall be enclosed as defined in § 42.13-15(j); and,
   2. (2)For vessels over 328 feet in length it need not comply with § 42.13-15(j) but shall be fitted with closing appliances to the satisfaction of the assigning authority.
3. (c)Vessels which, to suit exceptional operational requirements, cannot meet the requirements of paragraphs (a) and (b) of this section may be given special consideration by the assigning authority.