46 C.F.R. § 42.20-70
(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) For vessels below 820 feet in length,
0.672L[1−(L/1640)][1.36/(Cb + 0.68)] inches;
where: L is the length of the vessel in feet. Cb is the block coefficient which is to be taken as not less than 0.68.
(2) For vessels of 820 feet and above in length,
275.6[1.36/(Cb + 0.68)] inches;
where: Cb is the block coefficient which is to be taken as not less than 0.68.
(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:
[CGFR 68-60, 33 FR 10066, July 12, 1968, as amended by CGFR 68-126, 34 FR 9016, June 5, 1969]