tonnage which is the sum of the following capacities:

(1) The capacity under tonnage deck as obtained under the provisions of § 2.82;

(2) The capacity between decks as obtained under the provisions of § 2.83;

(3) The capacity of deck structures as obtained under the provisions of § 2.84; (4) The excess tonnage of hatchways as provided by § 2.85; and

(5) Light and air space added to the propelling machinery space under the provisions of § 2.59.

(b) The net tonnage referred to in §§ 2.87 through 2.100 is the net register tonnage which is the tonnage remaining after the authorized deductions have been made from the gross register tonnage.

§ 2.87 Single-tonnage and dual-tonnage assignments for vessels measured under the provisions of the optional dual-tonnage method.

(a) A single deck vessel shall be assigned only one gross tonnage and one net tonnage.

(b) A vessel having two or more complete decks may be assigned dual gross and net tonnages as follows:

(1) A higher gross tonnage applicable when the tonnage mark provided by § 2.89 is submerged.

(2) A higher net tonnage related to the higher gross tonnage;

(3) A lower gross tonnage applicable when the tonnage mark is not submerged; and

(4) A lower net tonnage related to the lower gross tonnage.

(c) A vessel having two or more complete decks may be assigned one gross tonnage and one net tonnage corresponding to the lower gross and net tonnages if the tonnage mark is placed at the level of the assiged load-line mark in accordance with the provisions of § 2.91(b).

watertight bulkhead placed aft of the rudder stock, is fitted with permanent means of watertight closing.

(b) The term "second deck" means the deck next below the uppermost complete deck which is continuous in a fore-andaft direction at least between peak bulkheads, is continuous athwartships, is fitted as an integral and permanent part of the vessel's structure, and has proper covers to all main hatchways. Interruptions in way of propelling machinery space openings, ladder and stairway openings, trunks, chain lockers, cofferdams, or steps not exceeding a total height of 48 inches shall not be deemed to break the continuity of the deck.

(c) The term "trunks" as used in the definition of second deck shall be deemed to refer to hatch or ventilation trunks which do not extend longitudinally completely between main transverse bulkheads.

(d) The "tonnage deck" is the "uppermost complete deck" of a single deck vessel and the "second deck” of a vessel having more than one complete deck.

§ 2.89 The tonnage mark and form of identification.

(a) The tonnage mark referred to in § 2.80 (b), (c), and (d) shall consist of a horizontal line 15 inches long and 1 inch wide. On the tonnage mark shall be placed for identification purposes an inverted equilateral triangle, each side 12 inches long and 1 inch wide, with its apex on the midpoint of the line. (See figure 54.)

(b) An additional line for fresh water and tropical waters may be assigned at a level higher than the tonnage mark.

tropical waters shall be 1⁄448 of the molded draft to the tonnage mark.

fresh

(2) The additional line for water and tropical waters shall be a horizontal line 9 inches long and 1 inch wide, measured from a vertical line, the latter 1 inch wide being marked at the after end of, and perpendicular to the tonnage mark.

(c) The upper edge of the tonnage mark and of the additional line for fresh water and tropical waters shall be designated by a welding bead or other similarly permanent means.

(d) The tonnage mark, the additional line for fresh water and tropical waters, the vertical line, and the triangle shall be maintained in a light color on a dark background or a dark color on a light background.

(e) The tonnage mark shall be deemed to be submerged at a salt water or brackish water port when the upper edge of the tonnage mark is submerged.

(f) The tonnage mark shall be deemed to be submerged at a fresh water port (one at which 100 percent of the fresh water allowance for load lines is permitted under tables published by the U.S. Coast Guard) when the upper edge of the additional line for fresh water and tropical waters is submerged. § 2.90

Longitudinal location of the tonnage mark.

The tonnage mark shall be placed on each side of the ship abaft amidships but as near thereto as practicable. In no case shall the apex of the triangle on the tonnage mark be less than 21 inches nor more than 6 feet 6 inches abaft the vertical center line of the loadline disk. (See k in figs. 55 and 56.) § 2.91

Vertical location of the tonnage

mark.

(a) The upper edge of the tonnage mark shall be at a distance below the molded line of the second deck determined according to the table in § 2.95. (See fig. 55.)

(b) When the load line assigning authority certifies that the load line is fixed at a place determined as though the second deck were the freeboard deck, the tonnage mark may be placed below that deck less than the minimum distance derived from the tonnage mark

a Distance from the molded line of second deck to upper edge of tonnage mark. d=Molded draft to upper edge of tonnage mark.

e Freeboard from loadline certificate. h=Molded draft to loadline. k=Distance from centerline of loadline disk to apex of triangle on tonnage mark. m=Distance from deck line to tonnage mark. t Distance from molded line of second deck to deck line for freeboard.

§ 2.92 Depth (D ̧) used with the tonnage mark table.

(a) The depth (D) to be used with the tonnage mark table in § 2.95 shall be the molded depth to the second deck.

(b) If the second deck is stepped, an equivalent depth shall be used. fig. 57.)

(See

(1) If the higher portion of the deck is less than one-half the total length (L) of both portions, the depth for the table (D) shall be the molded depth amidships (D) increased by the ratio of the length of the shorter portion (I) to the total length (L) times the height of the step (b).

I

(D=D+-b in the upper example in

L

fig. 57.)

(2) If the lower portion of the deck is less than one-half the total length (L) of both portions, the depth for the table (D) shall be the molded depth amidships (D) decreased by the ratio of the length of the shorter portion (I) to the total length (L) times the height of the step (b).

I

(D-D--b in the lower example in

L

fig. 57.)

§ 2.93 Length (L.) used in the tonnage

mark table.

(a) The length (L) as used in the tonnage mark table shall be the distance on the second deck between two points, of which the foremost is the point where the underside of that deck or the line thereof at the stem, meets the inner surface of the ceiling, sparring or frames, and the aftermost is the point where the underside of that deck, or the line thereof, meets the inner surface of the ceiling, sparring or frames in the middle plane at the stern.

No line of the second deck shall be marked on the side of the vessel.

§ 2.97 Line of the uppermost complete deck.

(a) For a vessel having no statutory loadline, the line of the uppermost complete deck shall be marked similarly to the deck line provided by the Load Line Convention.

(b) The deck line shall be a horizontal line 12 inches long and 1 inch wide. It shall be marked abaft amidships above the place on each side of the vessel prescribed in § 2.90 for the tonnage mark. Its upper edge shall pass through the point where the continuation outward of the upper surface of the freeboard deck intersects the outer surface of the shell. (See fig. 58.) Where the deck is partly sheathed amidships, the upper edge of the deck line shall pass through the point where the continuation outward of the upper surface of the actual sheathing at amidships intersects the outer surface of the shell.

§ 2.98 Placing the tonnage mark in relation to the deck line.

(a) As a practical matter, since the molded line of the second deck is not to be marked on the side of the vessel, the position of the tonnage mark shall be determined by reference to the deck line

for freeboard or, in the absence of such a line, with reference to the deck line provided by § 2.97.

(b) The upper edge of the tonnage mark shall be below the upper edge of the deck line, a distance equivalent to the sum of the vertical distance (determined by reference to the tonnage mark table) from the molded line of the second deck or equivalent to the upper edge of the tonnage mark plus the vertical distance from the molded line of the second deck or equivalent to the upper edge of the deck line. (See in figs. 55 and 56, a+t=m.)

(c) In the case of a vessel for which it is desired to have only one set of tonnages, the tonnage mark shall be placed at the level of the uppermost part of the loadline grid as provided by § 2.91(b). (See fig. 56.)

§ 2.99 Application for measurement according to the optional dual-tonnage method.

(a) Application of the owner or his agent for measurement of a vessel under the provisions of the optional dual tonnage method shall be submitted in duplicate together with supporting plans or sketches to the customs officer in charge of the district in which the vessel is or will be located.

FIGURE 58.-Deck line-12 inches x 1 inch

(b) The application shall include the following information: (See figures 55, 56, and 57.)

(1) Molded depth at midship section from second deck at side.

(2) Depth used with tonnage mark table.

(3) Length of shorter portion of stepped second deck if any.

(4) Total length of longer and shorter portions of stepped second deck.

(5) Length used with tonnage mark table.