beyond the after bulkhead and 50 percent of that beyond the forward bulkhead are effective.

CROSS REFERENCE: For class 1 and class 2 closing appliances, see §§ 43.15-37, 43.15-40.

$43.15-55 Forecastle. (a) Where there is an efficient bulkhead and the access openings are fitted with class 1 or class 2 closing appliances, the length to the bulkhead is effective. Where no closing appliances are fitted and the sheer forward of amidships is not less than the standard sheer, 100 percent of the length of the forecastle forward of 0.1L from the forward perpendicular is effective; where the sheer forward is half the standard sheer or less, 50 percent of that length is effective; and where the sheer forward is intermediate between the standard and half the standard sheer, an intermediate percentage of that length is effective; 50 percent of the length of an open extension beyond the bulkhead or beyond 0.1L from the forward perpendicular is effective.

CROSS REFERENCE: For class 1 and class 2 closing appliances, see §§ 43.15-37, 43.15-40.

§ 43.15-57 Trunk. (a) A trunk or similar structure which does not extend to the sides of the vessel is regarded as efficient: Provided, That,

(1) The trunk is at least as strong as a superstructure.

(2) The hatchways are in the trunk deck, and comply with the requirements of §§ 43.10-1-43.10-45 and the width of the trunk deck stringer provides a satisfactory gangway and sufficient lateral stiffness.

(3) A permanent working platform fore and aft fitted with guard rails is provided by the trunk deck, or by detached trunks connected to other superstructures by efficient permanent gangways.

(4) Ventilators are protected by the trunk, by watertight covers or by equivalent means.

(5) Open rails are fitted on the weather portions of the freeboard deck in way of the trunk for at least half their length.

(6) The machinery casings are protected by the trunk, by a superstructure of standard height, or by a deck house of the same height and of equivalent strength.

(b) Where access openings in poop and bridge bulkheads are fitted with class 1 closing appliances, 100 percent of the length of an efficient trunk reduced in the ratio of its mean breadth to B is added to the effective length of the superstructures. Where the access openings in these bulkheads are not fitted with class 1 closing appliances 90 percent is added.

(c) The standard height of a trunk is the standard height of a bridge.

(d) Where the height of the trunk is less than the standard height of a bridge, the addition is reduced in the ratio of the actual to the standard height; where the height of hatchway coamings on the trunk deck is less than the standard height of coamings (see § 43.10-10), a reduction from the actual height of trunk is to be made which corresponds to the difference between the actual and the standard height of coamings.

§ 43.15-60 Inclosed superstructure with middle line openings in the deck not provided with permanent means of closing. (a) Where there is an inclosed superstructure with one or more middle line openings in the deck not provided with permanent means of closing (see §§ 43.10-1-43.10-45), the effective length of the superstructure is determined as follows:

(1) Where efficient temporary closing appliances are not provided for the middle line deck openings (see § 43.15-43), or the breadth of openings is 80 percent or more of the breadth B, of the superstructure deck at the middle of the opening. the vessel is considered as having an open well in way of each opening, and freeing ports are to be provided in way of this well. The effective length of superstructure between openings is governed by §§ 43.15-47, 43.15-53, 43.15-55.

(2) Where efficient temporary closing appliances are provided for middle line deck openings, and the breadth of openings is less than 0.8B, the effective length is governed by §§ 43.15-47, 43.15-53, 43.15-55, except that where access openings in between deck bulkheads are closed by class 2 closing appliances, they are regarded as being closed by class 1 closing appliances in determining the effective length. The total effective length is obtained by adding to the length determined by subparagraph (1) of this paragraph the difference between this

length and the length of the vessel modified in the ratio of

B-b where b=breadth of deck
B1
opening

where

B-b is greater than 0.5, it is
B1
taken as 0.5
Deductions for superstruc-

§ 43.15-63

tures.

(a) Where the effective length of

§ 43.15-65 Sheer, general. (a) The sheer is measured from the deck at side to a line of reference drawn parallel to the keel through the sheer line at amidships.

(b) In vessels designed to trim by the stern in service, the sheer may be measured in relation to the load line, provided an additional mark is placed at 0.25 L forward of amidships to indicate the assigned load line. This mark is to be similar to the load line disk amidships.

(c) In flush deck vessels and in vessels with detached superstructures the sheer is measured at the freeboard deck.

(d) In vessels with topsides of unusual form in which there is a step or break in the topsides, the sheer is considered in relation to the equivalent depth amidships. (See § 43.15-15.)

(e) In vessels with a superstructure of standard height which extends over the whole length of the freeboard deck, the sheer is measured at the superstructure deck; where the height exceeds the standard, the sheer may be considered in relation to the standard height.

(f) Where a superstructure is intact or access openings in its inclosing bulkheads are fitted with class 1 closing appliances (§ 43.15-37), and the superstructure deck has at least the same sheer as the exposed freeboard deck, the sheer of the inclosed portion of the freeboard deck is not taken into account.

§ 43.15-67 Standard sheer profile. (a) The ordinates (in inches) of the

1 A. P. 2 F. P.

After end of summer load water line.
Fore end of summer load water line.

§ 43.15-70 Measurement of variations from standard sheer profile. (a) Where the sheer profile differs from the standard, the 7 ordinates of each profile are multiplied by the appropriate factors given in the table of ordinates. The difference between the sums of the respective products, divided by 18, measures the deficiency or excess of sheer. Where the after half of the sheer profile is greater than the standard and the forward half is less than the standard, no credit is allowed for the part in excess and the deficiency only is measured.

(b) Where the forward half of the sheer profile exceeds the standard, and the after portion of the sheer profile is not less than 75 percent of the standard, credit is allowed for the part in excess; where the after part is less than 50 percent of the standard no credit is given for the excess sheer forward. Where the

length of superstructure, as defined in § 43.15-27.

§ 43.15-75 Addition for deficiency in sheer. Where the sheer is less than the standard, the correction for deficiency in sheer (see § 43.15-73) is added to the freeboard.

§ 43.15-77 Deduction for excess sheer. (a) In flush deck vessels and in vessels where an inclosed superstructure covers 0.1 L before and 0.1 L abaft amidships, the correction for excess of sheer (see § 43.15-73) is deducted from the freeboard; in vessels with detached superstructures where no inclosed superstructure covers amidships, no deduction is made from the freeboard; where an inclosed superstructure covers less than 0.1 L before and 0.1 L abaft amidships, the deduction is obtained by interpolation. The maximum deduction for excess sheer is 11⁄2 inches at 100 feet and increases at the rate of 11⁄2 inches for each additional 100 feet in the length of the vessel.

§ 43.15-80 Standard round of beam. (a) The standard round of beam of the freeboard deck is one-fiftieth of the breadth of the vessel.

§ 43.15-83 Round of beam correction. (a) Where the round of beam of the freeboard deck is greater or less than the standard, the freeboard is decreased or increased respectively by one-fourth of the difference between the actual and the standard round of beam, multiplied by the proportion of the length of the freeboard deck not covered by inclosed superstructures. Twice the standard round of beam is the maximum for which allowance is given.

843 13 85 Summer freeboard. (a) The minimum freeboard in summer is the freeboard derived from the freeboard table after corrections for departures from the standards and after deduction

for superstructures. The freeboard in salt water measured from the intersection of the upper surface of the freeboard deck with the outer surface of the shell is not to be less than 2 inches.

§ 43.15-87 Tropical freeboard. (a) The minimum freeboard in the tropical zone is the freeboard obtained by a deduction from the summer freeboard of one-fourth inch per foot of summer draft measured from the top of the keel to the center of the disk. The freeboard in salt water measured from the intersection of the upper surface of the freeboard deck with the outer surface of the shell is not to be less than 2 inches.

§ 43.15-90 Winter freeboard. (a) The minimum freeboard in winter is the freeboard obtained by an addition to the summer freeboard of one-fourth inch per foot of summer draft, measured from the top of the keel to the center of the disk.

§ 43.15-93 Winter North Atlantic freeboard. (a) The minimum freeboard for vessels not exceeding 330 feet in length on voyages across the North Atlantic from a port or place of departure north of latitude 36° N. to a port or place of arrival north of latitude 36° N., regardless of the route of the vessel while it is in either of the northern seasonal winter zones during the winter season, shall be the winter freeboard plus 2 inches. For vessels over 330 feet in length it is the winter freeboard.

$43.15-95 Fresh-water freeboard. (a) The minimum freeboard in fresh water of unit density is the freeboard obtained by deducting from the minimum freeboard in salt water inches, where

40T A=displacement in salt water in tons at the summer load water line, and T tons per inch immersion in salt water at the summer load water line.

(b) Where the displacement at the summer load water line cannot be certified, the deduction is to be one-fourth inch per foot of summer draft, measured from the top of the keel to the center of the disk.

§ 43.15-97 Freeboard table for steamers. (a) Table 43.15-97 (a) gives the basic minimum summer freeboard for steamers which comply with the standards in this part.

(e) Where D exceeds 1 the freeboard

is increased by (D) R inches, where

L R is 130 and 3 at 390 feet length and above.

at lengths less than 390 feet,

(1) In a vessel with an inclosed superstructure covering at least 0.6L amidships with a complete trunk or with a combination of intact partial superstructures and trunk which extends all L

15

fore and aft, where D is less than the freeboard is reduced at the above rate.

(2) Where the height of superstructures or trunk is less than the standard height, the reduction is in the ratio of the actual to the standard height.

(f) Where the actual depth to the surface of the freeboard deck amidships is greater or less than D, the difference between the depths (in inches) is added to or deducted from the freeboard.

WNA

-12" 18"

FIGURE 43.20-1 (a)

§ 43.20-5 Conditions of assignment of sailing vessel load lines. (a) The conditions of assignment for sailing vessels are those contained in §§ 43.10-1— 43.10-100.

§ 43.20-10 Computation of freeboard, sailing vessels. (a) Freeboards are computed from the freeboard table for sailing vessels in the same manner as the freeboards for steamers are computed from the freeboard table for steamers, except as provided by §§ 43.20-1543.20-45.

§ 43.20-15

Depth for freeboard, sailing vessels (D). (a) In sailing vessels having a greater rate of rise of floor than 11⁄2 inches per foot, the vertical distance from the top of keel (§ 43.15-7) is reduced by half the difference between the total rise of floor at the half breadth of the vessel and the total rise of 11⁄2 inches per foot; 21⁄2 inches per foot of half breadth is the maximum rate of rise for which a deduction is made.

(b) Where the form at the lower part of the midship section is of a hollow character, or thick garboards are fitted,

The provisions of §§ 43.01-1-43.01-100 and 43.05-1-43.15-97, inclusive, apply to sailing vessels, except as modified by §§ 43.20-1-43.20-45, inclusive.