(a) Where the effective length E of superstructures and trunks that meet the requirements of subpart D of this part is 1.0L, the minimum summer freeboard may be corrected by subtracting 1⁄2 Hs.

(b) Where the effective length of superstructures and trunks is less than 1.0L the minimum summer freeboard may be corrected by subtracting a percentage of one-half of the standard superstructure height (Hs) determined by the formula:

Percentage = (E/2L) (1 + E/L) × 100

(c) To be eligible for the correction a trunk must—

(1) Be at least as strong and as stiff as a superstructure;

(2) Have no opening in the freeboard deck in way of the trunk, except small access openings;

(3) Have hatchway coamings and covers that meet §§45.143 through 45.147;

(4) Provide a permanent working platform fore and aft with guardrails;

(5) Provide fore and aft access between detached trunks and superstructures by permanent gangways;

(6) Be at least 60 percent of the breadth of the ship in way of the trunk; and

(7) Be at least 0.6 L in length, if no superstructure, is provided.