(a) A measure from the outboard face of the outer skin on one side to the same point opposite, taken at or below the upper deck and at the widest part of the hull is the register breadth. (See Figure 4 (2.65).)

(b) A practical method for finding the register breadth is, to add twice the sum of the depth of the vessel's side frames and thickness of outer skin, plus an allowance for thickness of ceiling, insulation or cargo battens if fitted, to the greatest tonnage breadth.

§ 2.20 Register depth.

(a) The register depth is taken at the middle of the tonnage length from the under side of the tonnage deck, or line of same, down to the top of the floors at the side of the keelson; or to the ordinary floor timbers or plates when fitted; or to the inner bottom plating (tank top) of a cellular double bottom; as the case may be, in a direction perpendicular to the keel.

(b) Should ceiling be fitted on the above mentioned bottom members, the register depth shall be measured to the top of same and to this dimension shall be added the height of grounds, battens or other type of support for the ceiling. (See Figures 4 and 5 (§ 2.65).)

(c) If the vessel is measured in parts, as explained later, the register depth is taken at one-half the tonnage length of the vessel.

§ 2.21 Upper deck to the hull.

The uppermost complete deck, which extends from stem to stern and from side to side at all points of its length and below which there are no openings through the hull as required in shelter deck spaces and also having its hatchways or other openings provided with means for closing them against the action of the sea and weather upon the space below enclosed by the sides of the vessel, making the said space a fit place for the stowage of general cargo, is to be considered the upper deck to the hull. § 2.22 Enumerating the decks.

In enumerating the number of decks, only those which are without such openings as exempt the spaces beneath from

being included in the tonnage under the upper deck are to be considered. Other decks, if any, containing such openings as exempt the spaces beneath from inclusion in tonnage should be separately described after the number of decks proper; e. g., "Two decks and shelter deck," or as the case may be. Partial decks, forward or aft, such as orlop decks, are not considered as decks. §2.23 Register height.

The height from the top of the tonnage deck planking and/or plating to the underside of the planking and/or plating of the upper deck to the hull shall be deemed the register height of the upper deck to the hull above the tonnage deck.

[T.D. 66-57, 31 F.R. 4295, Mar. 11, 1966] § 2.24 Round of beam.

(a) The round of beam (camber) is the perpendicular distance down from the crown of the under side of the tonnage-deck plank or plating at the center to a line stretched athwart the vessel from end to end of the top of the beam and is to be ascertained at every place where it is to be used in the measurement. (See Figures 6 and 16 (§ 2.65).)

(b) The round of beam of the tonnage-deck, which must be known before taking the tonnage length, as well as before measuring the depths of the tonnage sections, may be taken either at the under side of the deck by stretching a small line tightly from end to end at the top of the beam, which will show the round or camber of the beam at the center; or it may be taken, if more convenient, at the upper side of the deck by stretching a line tightly across, held at equal heights from the deck at each side of the vessel, so as just to touch the crown of the deck at the middle line; then the distance from the deck to the line at the vessel's sides gives the round of beam. (See Figure 6 (§ 2.65).) It is necessary to take the round of beam at each point of division of the length except when the vessel has a flat deck or one practically so. In lieu of the above methods, it may be ascertained on the basis of one-fourth of an inch to the foot of beam at each section in iron or steel vessels of the usual camber of beam. This method is more accurate and easier of application than the others.

(c) When the round of beam is 0.15 foot or less, it may be ignored. § 2.25 Pitch of beam.

(a) In vessels whose tonnage deck has a pitch instead of a round from its side at the shell plating to its center, find the height of the pitch of the beam at each tonnage section. It may be done in any practical manner.

(b) The height of the pitch of the beam is the perpendicular distance from the apex at the under side of the tonnage deck plank or plating at the center of the deck down to a straight line from end to end of the top of the beam. (See Figure 7 (§ 2.65).)

§ 2.26 Tonnage deck.

(a) Except as to a vessel having its tonnage deck determined under the provisions of § 2.88 (d), the tonnage deck is the upper deck to the hull in vessels having not more than two decks, and the second from the keel in vessels having more than two decks.

(b) If the tonnage deck consists of several partial decks extending with breaks from stem to stern, and if the partial decks are at different heights, the line of the lowest deck will be taken as the tonnage deck, and the headroom above such line under the higher deck or decks will be measured as a break.

(c) Engine and boiler casings, peak tanks and cofferdams are not considered as breaking the continuity of a deck. (See Figures 8 and 9 (§ 2.65).)

[28 F.R. 14553, Dec. 3, 1966, as amended by T.D. 66-57, 31 F.R. 4295, Mar. 11, 1966]

§ 2.27 Tonnage length.

The tonnage length is the longitudinal distance on the under side of the tonnage deck, or line of same from a point where the line of the inboard faces of the side frames, or ceiling thereon if any, intersects the side of the stem, to a point aft on the inboard face of the stern timber or cant frame, or ceiling if fitted thereon. (See Figures 10 and 11 (§ 2.65).)

§ 2.28 Depth of a transverse section.

(a) Depth. The depth of a tonnage section is a measurement taken at its proper point of division of the tonnage length, from a point at a distance below the tonnage deck equal to onethird of the round or one-half of the pitch of the beam, down to the upper side of the floor timbers or floor plates; or

bottom floors alongside the keelson; or longitudinals; or the tank top of a cellular double bottom, as the case may be.

(b) Ceiling. If ceiling is fitted on the bottom floor members, depths of transverse sections terminate on the upper face of the ceiling of average thickness. (See Figure 4 (§ 2.65).) For tonnage depths where ceiling is fitted on tank top, see Figure 5 (§ 2.65).

(c) Raised platform. In vessels with a raised platform in the bottom and no ceiling fitted on the bottom frame members, the depths are to be taken down through the platform to the upper side of the floor timbers or floor plates as described above, deducting therefrom the thickness of the ceiling of the platform in question.

(d) Depths in way of interruptions to tonnage deck. Should depths of transverse sections fall where the tonnage deck is interrupted, due to a break, hatches, etc., then depths are taken from the line of continuation of the tonnage deck.

(e) Rise of double bottom. In vessels having a double bottom the tank top of which, in way of tonnage sections, rises from the center line to the wings, the tonnage depth of each section will terminate at one-half height of the dead rise. (See Figure 12 (§ 2.65).)

(f) Fall of double bottom. In vessels having a double bottom the tank top of which, in way of tonnage sections, has a straight fall from the center line to the wings the tonnage depth of each section will terminate at one-half height of fall. (See Figure 13 (§ 2.65).)

§ 2.29 Tonnage depths.

(a) The tonnage depth. The depth generally referred to as "the tonnage depth" is located at the middle point of division of the tonnage length and is found in a manner similar to the other depths of transverse sections.

(b) Tonnage depth in a vessel measured in parts. Should a vessel be required to be measured in parts, and each part measured as a separate unit; then a tonnage depth shall be found for each part or unit at one-half its tonnage length. (See Figure 14 (§ 2.65).)

(c) Tonnage depth is the first depth measured. The tonnage depth governs the number of parts into which it and all the remaining depths of the part in which said depth is located, is divided.

(d) Divisions of tonnage depth. If the tonnage depth at the middle of the tonnage length of the vessel or part of same does not exceed 16 feet, divide each depth into 4 equal parts; but if the depth at the middle of said length exceeds 16 feet, divide each depth into 6 equal parts.

(e) Intervals. The common intervals between the points of division of depths, also one-third common intervals are to be carried to the nearest hundredth of a foot.

(f) Purpose for dividing tonnage depths. Depths are divided to indicate points at which tonnage breadths are to be measured.

§ 2.30 Tonnage breadths.

(a) Breadths. An inside horizontal breadth is to be measured at each point of division of the depth marked on the sliding rods placed in position as directed in § 2.13(b) and also at the upper and lower points of the depth. Extend each measurement to the inboard face of the ordinary frames, or line of same, or inboard face of ceiling, or battens, or insulation of average thickness if fitted. (See Figure 15 (§ 2.65).) Care must be taken that the sections shall be parallel to each other and at right angles to the axis of the vessel.

(b) Upper breadth. In finding the upper breadth of each transverse section make no allowance for the excess of the deck-beam shelves, etc., over the permissible thickness of ceiling, if any, thereunder.

Referring to Figure 16 (§ 2.65), observe that after the deck is laid the upper breadth (represented by the line U B) passes through the deck on each side. Hence, it is impossible to take it at its true position. In such cases take it on the deck, allowing within the extended line of frames the thickness of the ceiling if any on the frames under deck, as shown by line T B in the figure.

Owing to deck-beam shelves or other obstructions, it can be more conveniently and accurately taken here than under the deck, and, besides it will be only a few inches from its true position. In vessels which have upright sides the said breadth so taken will be correct, but in the case of vessels with inclining sides the necessary allowance must be made for the deviation of the sides from the upright in the few inches above the true position of the said breadth.

Bottom

(c) Bottom breadths. breadths are taken only so far as the flat of the floor extends. (See B B, Figures 4 and 5; Figure 15; and B B, Figures 17 and 18 (§ 2.65).)

When bottom frames rise immediately from the keelson, or combined keel and keelson, and bona fide floor timbers or floor plates are not fitted, bottom breadths are equal to the breadth of keelson, or combined keel and keelson as the case may be. (See B B, Figure 19 (§ 2.65).)

The bottom breadths of transverse sections of vessels of longitudinal construction falling in the hold where there is no double bottom and where there is a dead rise of the bottom out to the sides of the vessel may be considered to be equal to that part of the bottom plating not affected by dead rise.

(d) Bottom breadths in case of rise or fall of double bottom. Bottom breadths falling in way of a double bottom the top of which rises or falls from the midship longitudinal plane to the wings are measured from and to the inboard end of the frame brackets (or ceiling thereon if fitted), connecting the double bottom with the frames. B, Figures 12 and 13 (§ 2.65).) § 2.31 Measuring the tonnage length.

(See B

(a) The cubic capacity of the space below the tonnage deck is determined by use of the tonnage length together with the areas of a prescribed number of transverse sections as hereinafter described.

(b) To determine the extreme points of the tonnage length as indicated by § 2.27 and T L in Figures 10 and 11 (§ 2.65), observe the following:

(1) Vertical bow and stern. In vessels having a vertical bow, also a vertical stern, both above and below the tonnage deck, measure horizontally the depth of frames, also the thickness of ceiling thereon if any, at the extreme forward and after ends immediately under the tonnage deck. Mark these measurements on the upper side of the tonnage deck, from the outer shell and in the direction in which the frames were measured. Then draw through the points thus obtained, lines parallel to the shell. The forward and after points of intersection of these lines indicate the points from and to which the tonnage length is to be measured.

(2) Raked bow or stern. In the case of vessels having a raked bow or stern at the level of the tonnage deck, the extreme points of the tonnage length are, when practicable, to be determined at the under side of the tonnage deck. The distance from these points to a hatch coaming, bulkhead, etc., should be measured and transferred to the upper side of the tonnage deck as indicated in Figure 20 (§ 2.65).

(c) Should it be impracticable to determine the extreme points of the tonnage length at the under side of the tonnage deck, and should the thickness of this deck be considerable, as in the case of a wooden deck, the rake of the bow or stern within the thickness of the deck is to be taken into account. This is done after having first proceeded as indicated in paragraph (b) (1) of this section by measuring the thickness of the tonnage deck and determining by means of a hinged rule, or any other instrument for finding angles under similar circumstances, the angle of the rake which the bow or the stern forms with the tonnage deck. Transfer thereafter this angle on the deck by drawing the lines A B C shown in Figure 21 (§ 2.65), A B represents the upper side of tonnage deck and B C the after side of the stem or the inside of the shell at the stern, as the case may be. The perpendicular B D represents the thickness of the tonnage deck. The points T, L, in Figures 10 and 11 (§ 2.65) marked on the upper side of the tonnage deck are then to be moved forward at the stern or aft at the stem, as the case may be, for a distance equal to D E, representing the rake within the thickness of the deck.

(d) It should be borne in mind that the condition for applying the method of setting out the angles on the upper side of the tonnage deck is that the stem or stern have the same angle of rake above and immediately below the tonnage deck. If the angle of rake at or immediately below the tonnage deck is a different one, then this last angle must be used.

(e) Should a vessel as referred to in paragraph (b) (2) of this section have a square bow or stern, it will be necessary to make a correction for camber where such exists. This is done by increasing the thickness of the deck B D in Figure 21 (§ 2.65) by one-third of the round or one-half of the pitch of beam at the extreme point of the tonnage length.

(b) The points of division of the tonnage length, also each end of the length indicate the common intervals at which a depth is measured.

Intervals and one-third intervals are to be carried to the nearest thousandth of a foot.

§ 2.33 Transfer of location of sections to keelson.

(a) The tonnage length having been ascertained and the number of sections to be measured and the interval between them determined, a line is then to be extended down the main hatchway, at the middle line of the vessel, in a perpendicular direction.

(b) The distance of the midship tonnage section is then to be set off from this line in the same direction on the keelson, which gives the position of the midship section on the keelson, and the positions of the other sections are obtained on the keelson by setting off forward and abaft the midship section the common interval between sections as already determined.

The position of the midship tonnage section may be determined by any other practical means.

§ 2.34 Transverse areas, rule for finding.

(a) Assuming the tonnage length exceeds 250 feet requiring that it be divided into 16 equal parts, and the tonnage depth at the middle of the tonnage length exceeds 16 feet, requiring it to be divided into 6 equal parts:

(1) Measure the depth at each of the 15 points of division of the length as required, also at the extreme forward point (Section 1) and at the extreme after point (Section 17) of the length. (See Figure 22 (§ 2.65).)

(2) The extreme points of the length at the bow and stern, though described as being the positions of the first and last areas, do not in vessels of usual form yield any area for practical purposes. Therefore, in the computation for tonnage, where the first and last sections yield no areas, a cipher must be employed in their places. In vessels of unusual form, as, for instance, in barges or other craft in which the bow and stern are upright, with breadth also at those places, sections at the extreme points of the length will yield areas; in which cases such areas must be measured and used in the computation.

(3) Then measure the inside horizontal breadth at each of the five points of division of the depth, also at the upper and lower points of the depth.

(4) Number the breadths from above, numbering the upper breadth 1 and so on down to the lowest or seventh.

(5) Multiply the second, fourth and sixth by 4, and the odd numbered breadths by 2, except the first and last which are multiplied by 1.

(6) Add these products together.

(7) Multiply the sum thus obtained by one-third of the common interval between the breadths, and the product shall be deemed the transverse area.

(8) This process will be repeated for every section.

(b) Having thus ascertained the transverse area at each point of division of the length of the vessel, also at each end of the length if they yield areas, as required above, proceed to ascertain the register tonnage of the vessel in the following manner:

(1) Number the areas successively 1, 2, 3, etc., No. 1 being at the extreme limit of the length at the bow and the last number at the extreme limit of the length at the stern.

(2) Then multiply the second and every even numbered area by 4 and the third and every odd numbered area by 2, except the first and last which are multiplied by 1.

(3) Add these products together and multiply the sum thus obtained by onethird of the common interval between the areas, and the product will be the contents in cubic feet of the spaces under the tonnage deck.

(4) Divide this product by 100, and the quotient, being the tonnage under the tonnage deck shall be deemed the

register tonnage of the vessel, subject to the additions hereinafter mentioned.

(c) In every case when finding the capacity under tonnage deck, or a part thereof; whether the length be divided according to the table into 6 or 16 parts, as in classes 1 and 6, or in 2 or 4 parts as provided for in § 2.35 (a) and the depths into 4 or 6 parts, thus requiring 5 or 7 breadths respectively to be taken; the above formula shall be used; i. e., even numbered breadths shall be multiplied by 4, and odd numbered ones by 2 except the first and last which are multiplied by 1. Similarly when running areas through the multipliers, the even numbered ones shall be multiplied by 4 and odd numbered ones by 2, except the first and last, which are multiplied by 1.

§ 2.35 Breaks in double bottom.

(a) The tonnage length of a vessel having a break exceeding one-half of a foot in height, or a number of such breaks in the line of her double bottom, is to be divided into longitudinal parts establishing transverse vertical planes at such breaks. The length of each such part so found is then to be divided into a number of equal parts according to the class in the above table to which it belongs, just as if it were the length of a separate vessel: Provided, That such parts as are 20 feet or under in length may be divided into 2 equal parts, and those above 20 feet and not exceeding 40 feet in length may be divided into 4 equal parts instead of into 6, as indicated in the table in § 2.32 (a).

(b) When a vessel is required to be measured in parts, and each part measured as a separate vessel, the sum of the tonnages of the several parts is the capacity under the tonnage deck.

§ 2.36 Vessels having side tanks may be measured in parts.

Vessels having side tanks extending above the floor line or double bottom, and through which tanks tonnage breadths normally pass, may be measured in parts. The length of the first part will extend aft to the line of the forward bulkheads of the side tanks. (See Figures 23 and 24 (§ 2.65).) The length of the second part is equal to the length of side tanks, and the depths extend, at proper intervals under the tonnage deck, down to athwartship lines forming con

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