Coast Guard, Dept. of Homeland Security § 45.77

The superstructure deck must not be (2) For vessels having a length great- less than standard height above this er than 550 feet, curve at any point. This curve must be (341.6—0.227 L) inches—actual bow height used in determining the sheer profile for forward and after halves of the ves- (b) Where the bow height is obtained sel. by sheer, the sheer must extend for at (e) The maximum decreased for ex- least 15 percent of the length of the cess sheer must be no more than 11⁄2 vessel measured from the forward per- inches per 100 feet of length. pendicular. (f) Where the deck of an enclosed su- (c) Where the bow height is obtained perstructure has at least the same by a superstructure, the superstructure sheer as the exposed freeboard deck, must be enclosed and extend from the the sheer of the enclosed portion of the stem to a point at least 0.06 L abaft the freeboard deck cannot be taken into forward perpendicular. account. (d) Vessels which, to suit exceptional operational requirements, cannot meet § 45.67 Sheer measurement. the requirements of paragraph (c) of (a) The sheer is measured from the this section may be given special con- freeboard deck at side to a line of ref- sideration by the Commandant. erence drawn parallel to the keel (e) The bow height is defined as the through the sheer line at amidships; vertical distance at the forward per- (b) In ships designed with a rake of pendicular between the waterline cor- keel or designed to trim by the stern, responding to the assigned summer the sheer must be measured in ref- freeboard at the designed trim and the erence to a line drawn through the top of the exposed deck at side. sheer line at amidships parallel to the design load waterline. § 45.71 Midsummer freeboard. (c) In flush deck ships and in ships The minimum midsummer freeboard with detached superstructures, the (fms) in inches is obtained by the for- sheer must be measured at the mula: freeboard deck. fms=f(s)¥0.3Ts (d) In ships with a step or break in the topsides, the sheer must be meas- where: ured from the equivalent depth amid- f(s)=summer freeboard in inches ships. Ts=distance in feet between top of keel and (e) In vessels with a superstructure of the summer load line. standard height that extends over the whole length of the freeboard deck, the § 45.73 Winter freeboard. sheer must be measured on the super- The minimum winter freeboard (fw) structure deck. Where the height of su- in inches is obtained by the formula: perstructure exceeds the standard, the fw=f(s)+T s (200)/L least difference (Z) between the actual and standard heights must be added to where: each end ordinate. Similarly, the inter- L=length L in feet but not less than 400 feet. mediate ordinates at distance of 1⁄6 L and 1⁄3 L from each perpendicular must § 45.75 Intermediate freeboard. be increased by 0.444 Z and 0.111 Z re- The minimum intermediate spectively. freeboard (fI) in inches is obtained by the formula: § 45.69 Correction for bow height. f =f(s)+T s(100)/L (a) The minimum summer freeboard I of all manned vessels must be increased where: by the same amount in inches as any L=length L in feet but not less than 400 feet. deficiency which may be shown by the following formulas: § 45.77 Salt water freeboard. (1) For vessels having a length of not (a) The salt water addition in inches less than 79 feet and not greater than to freeboard applicable to each fresh 550 feet, water mark is obtained by the formula: 0.593 L (1.0–L/1640) inches—actual bow height Addition=D/41T 81

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where: § 45.109 Strength of superstructures D=displacement in fresh water, in tons of and deckhouses. 2,240 pounds, at the summer load water- Each superstructure or deckhouse line. T=tons per inch immersion, of 2,240 pounds, used for accommodations of the crew in fresh water at the summer load water- must be approved by the Commandant line. or the approved assigning authority with regard to general strength and (b) When the displacement at the weathertightness. The Commandant summer load waterline cannot be cer- may use the requirements of the as- tified, the addition in inches to the signing authority as a guide. minimum freeboard in fresh water may be obtained by multiplying 0.25 by the § 45.111 Strength of bulkheads at ends summer draught in feet measured from of superstructures. the top of the keel to the center of the Bulkheads at ends of enclosed super- load line diamond. structures must have sufficient strength to withstand impact of board- Subpart D—Conditions of ing seas. Assignment § 45.113 Access openings in bulkheads § 45.101 Purpose. at ends of enclosed superstructures. This subpart prescribes conditions (a) Access openings in bulkheads at that a vessel must meet to be eligible ends of enclosed superstructures must for assignment of a loadline under this have doors of steel or material as part. strong as steel that are permanently attached to the bulkhead and framed, § 45.103 Structural stress and stability. stiffened, and fitted so that the bulk- (a) The nature and stowage of the head and door are as strong as the cargo, ballast, and other variable bulkhead and weather tight when weights must be such as to make the closed. vessel stable and avoid unacceptable (b) The means for securing the doors structural stress. weathertight must be permanently at- (b) The vessel must meet all applica- tached to the doors or bulkheads and ble stability and subdivision require- arranged so that the doors can be se- ments of this chapter. cured weathertight from both sides of the bulkhead. § 45.105 Information supplied to the (c) Access openings in bulkheads at master. ends of enclosed superstructures must Unless otherwise authorized by the have sills that are at least 12 inches Commandant, the vessel must have on- above the deck. board, in a form approved by the Com- mandant, sufficient information. § 45.115 Bulwarks and guardrails. (a) To enable the master to load and (a) The exposed parts of freeboard ballast the vessel in a manner that and superstructures decks and deck- avoids unacceptable stresses in the ves- houses on the freeboard deck must sel’s structure; and have guardrails or bulwarks that are at (b) To guide the master as to the sta- least 36 inches high above the deck. bility of the ship under varying condi- (b) Guardrails must have at least tions of service. three courses with no more than a 9- inch opening below the lowest course § 45.107 Strength of hull. and no more than 15 inches between The general structural strength of other courses. If the sheer strake pro- the hull must be sufficient for the jection is at least 8 inches above the draught corresponding to the freeboard deck, a guardrail may have two courses assigned and must be approved by the with no more than 15 inches between Commandant. Ships built and main- courses. tained in conformity with the require- (c) In way of trunks at least half the ments of a classification society may protection required by paragraph (a) of be recognized by the Commandant as this section must be in the form of possessing adequate strength. open rails.

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