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but this allowance shall in no case exceed 100 tons. In the case of vessels of less than 100 gross tons this deduction shall not exceed 1 ton.

(d) Chart room. (1) The space for keeping the charts, nautical instruments and for plotting the course. When the space is a combined wheel and chart room, such part as is not exempted as wheelhouse shall be deducted.

(2) In small vessels requiring the use of navigation charts, and where the cabin or saloon is the only space available for filing or use of such charts, one-half of the cabin or saloon, may be allowed for this purpose provided the allowance does not exceed 11⁄2 tons.

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(e) Donkey engine and boiler. The space occupied by a donkey engine and boiler, if situated within the boundary of the engine room or the casing above it, and if the donkey engine is used as an auxiliary in connection with the main machinery for propelling the vessel and this space forms part of the actual engine room it shall not be subject to a separate allowance.

(2) When the donkey engine and/or boiler is in a house above the upper deck and not used in connection with the main propelling machinery as described above, the space thus occupied is an exemption and therefore must not be included in the gross tonnage of the vessel.

(3) In all other cases the space occupied by the donkey engine and boiler, if same are connected with the main pumps (except cargo pumps) of the vessel, is to be allowed as a deduction from the gross tonnage, if reasonable in extent. It must be certified in the same manner as other deductible spaces.

(f) Dynamo spaces. The space or spaces when reasonable in extent, occupied by dynamos, switchboards and apparatus necessary for the operation of same, when located below the upper deck shall be deducted regardless of the service for which the dynamo or dynamos are used.

(g) Pump room. A pump room or space below the upper deck containing the pumps of the vessel which are used solely for handling ballast, feed water, water for cleansing purposes, and for freeing the ship of water entering her hold, etc., shall be deducted as pump room. A pump room or space below the upper deck containing pumps primarily used for handling cargo, as in the case of bulk-oil carriers, shall not be deducted. The portion of either of the

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(a) Engine room must be measured. Notwithstanding the ratable allowance for propelling power for which the act of March 2, 1895 (28 Stat. 741; 46 U.S.C. 77) provides, it is necessary to measure the engine room, regardless of size, in order to ascertain whether the allowance to be deducted for propelling power shall be regulated by a percentage of the gross tonnage or by the actual tonnage of the engine room ascertained by measurement.

(b) Spaces included in engine room must be in gross tonnage. No space shall be included in the tonnage of the engine room unless it has first been included in the vessel's gross tonnage.

(c) Deductions from engine room. Conversely the spaces occupied by cabins, storerooms, etc., and any space not used in connection with propelling the vessel but included in the tonnage of the engine room through process of measurement must be subtracted therefrom. § 2.52

Spaces included in engine room.

The space occupied by the engine room is to be understood to include not only that occupied by the engine room itself but also the space occupied by the boiler room, together with the spaces strictly required for the working of the engines and boilers, and consisting of the following items:

(a) Space below the crown. The crown or top of the main space of the actual engine room, from which the depths of the main space are to be taken, will either be at the under side of a deck or, if the side bulkheads are sloping, at the point or height at which the slope terminates. (See Figures 49 and 50 (§ 2.65).)

(b) Space between crown and upper deck. Space between the crown and the upper deck framed in for the machinery or for admission of light and air thereto.

(c) Space above upper deck. Space similarly framed in above the upper deck when permitted under paragraph (i), act of March 2, 1895 (28 Stat. 741; 46 U. S. C. 77).

(d) Shaft tunnels, etc. The shaft setunnel or tunnels and the thrust block recess.

(e) Escape shaft. The trunked ladSderway leading from the after end of the Beshaft tunnel to the deck, provided that

it is no larger than is necessary for the purpose of access to and escape from the shaft tunnel. The part of an escape shaft above the upper deck line, also the and companion sheltering the escape shaft, is ct accorded the treatment of light and air space.

(f) Fuel oil transfer pump. (1) When de the fuel oil transfer pump is located in a separate space, this space, if reasonable hal in size, may be considered propelling machinery space provided said pump is not the used for bunkering the vessel.

(2) Should such pump perform the dual service of handling both ballast and transferring fuel oil to the settling tanks, one-half the space may be credited to propelling machinery space.

(g) Settling tanks. (1) Fuel oil settling tanks used solely for rendering crude oil fit for consumption in the main boilers are considered as part of the propelling machinery space.

(2) The permissible allowance for settling tanks is based on a 4 days' supply under full steam, which allowance must not exceed 1 percent of the vessel's gross tonnage.

(h) Engineers' stores and workshops. The engineers' stores, and/or workshops n are regarded as part of the engine room, up to three-quarters of 1 percent of the le gross tonnage, if in the engine room, th open to same, or separated therefrom me only by a screen bulkhead and located below the upper deck.

$2.53 Length of engine room. che (a) As a rule, the length of the engine he room extends from the bulkhead forward

of the boilers to the one aft of the engines; but if these bulkheads limit a space a considered excessive in length for the proper working of the boilers and en5gines, then that length only which is requisite for containing and operating the boilers and machinery, is to be allowed, with the addition of such length as is necessary for the stoking or working

of the fires when the furnaces are in a fore-and-aft direction.

(b) No such additional length is, however, required when the boilers are placed with the furnaces athwartship. The clear central space allowed between the boilers when the stoking is athwartship should be sufficient for this purpose. The point to which the after boundary of the length of the engine room is to be measured should be such as to provide sufficient space for the safe operation of the engine.

(c) The measurer should allow such length between the engines and boilers as may appear to him necessary for the safe working of the machinery.

§ 2.54 Boilers and engine in same compartment.

The boilers and engine are considered to be in the same compartment when there is a transverse bulkhead, screen or otherwise, through which the boilers project into the engine space, and where there is only sufficient space between the boilers and engine for the safe working of the machinery.

§ 2.55

Engine room measured in parts.

If the boilers and engine are entirely in separate rooms, or if there is a break or breaks in the bottom or side lines of the propelling machinery space resulting from a break or breaks in the double bottom or varying height of floors thereunder, or from side bunkers or other spaces not considered propelling machinery spaces, measure each room separately as a whole or in parts, according to the number of breaks in its bottom or side lines, and the sum of the several results shall be deemed to be the tonnage of the said spaces.

§ 2.56

Rule for measuring engine room. (a) Space in hold amidship. When the propelling machinery (boilers and engine) space is in the hold amidship, and without a break in its bottom or side lines, measure its length between the foremost and aftermost bulkheads or limits of its length, excluding such parts, if any, not actually occupied by or required for the proper working of the machinery. Divide the length by 2 and measure 3 depths of the space, one at each end and one at the middle of the length, taking the depths from the crown, or line of same, to the ceiling on

the bottom frames or floor timbers, or to the inner plating (tank top) of the double bottom in the case of a steel vessel. Measure also a breadth at each end and at the middle of the length, the said breadths to be taken at onehalf their respective heights. Find the product of the length, mean breadth and mean depth, which product divide by 100 and the result shall be deemed the tonnage of the main space below the crown.

(b) Spaces between the crown and upper deck. Find the cubical contents of the space or spaces, if any, between the crown aforesaid and the upper deck, or line of same, which are framed in for the propelling machinery or admission of light and air thereto, by multiplying together the length, breadth and depth thereof. Divide the product by 100; add the quotient to the tonnage of the space below the crown and the result shall, subject to the provisions hereinafter contained, be deemed the tonnage of the space.

(c) Engine room in after end. When the propelling machinery space is located in the after end of the hold of a vessel and extends from side to side of same and has a continuous bottom line, divide its length into such an even number of parts as will give a common interval most nearly equal to that used in finding the tonnage of the hold in that part of the vessel; then proceed to find its contends by the use of areas of transverse sections taken at each end and at each point of division of its length. In other words, measure it by the same method as was used for finding the tonnage of that part of the hold in which it lies.

(d) Shaft tunnel and thrust recess. (1) In the case of screw propelled vessels in which the top of the shaft tunnel is flat, the tonnage of such tunnel shall be ascertained by dividing the product of its length, breadth and depth by 100.

(2) In like manner find the tonnage of the thrust recess or entrance to the shaft tunnel.

(3) If the space abaft the shaft tunnel extends from side to side of the vessel, find its tonnage by using the formula for measuring peak tanks. (See Figures 47 and 48 (§ 2.65).)

(e) Round top shaft tunnel. When the top of the tunnel is practically semicircular in shape, find the area of

a transverse section in two parts; first the lower part from the bottom of the trunk up to where the curve begins by multiplying the breadth by the applicable height, and then the semicircula) part by taking half the area of a circle whose diameter equals the breadth of the tunnel. Multiply the sum of the two areas by the length and divide the product by 100. (See Figure 51 (§ 2.65) wherein B and H equal the breadth and height, respectively, of the lower part and r equals the radius of the semicircular top.)

(f) Shaft space and thrust recess not cased. (1) When the shaft is not en closed by a tunnel, the following rules should be observed in the case of a vessel with a single screw. The thrustblock space should be of such length and breadth as will permit of the proper care of the thrust-block and the height should not exceed 7 feet. The shaft space allowed should be of the dimensions of the usual tunnel suitable for the vessel and the height of this space should not exceed 6 feet.

(2) When the vessel is a twin screw and the space aft of the engines is open from side to side, the space should not be included in the engine room measurement for a greater height than 6 feet mean, and any space therein appropriated for stores or for any purposes other than the propelling machinery should be subtracted from the space to be included in the engine room. § 2.57 Engine room in small boats.

(a) When not bulkheaded off. In the case of a motorboat not having an engine room bulkheaded off from the rest of the hold, allow as engine space the space occupied by the engine and suffi cient space on each side and end of itsay, about 2 feet-to permit the oper ator to handle it safely and efficiently if sufficient space does not exist for such allowance then allow whatever space there is. Fuel tanks are not to be in cluded in the said engine space.

(b) When bulkheaded off. If the en gine room is bulkheaded off from the rest of the hold and is larger than is strictly required for safe and efficient handling of the engine, limit the engine space according to the said requirements and as indicated in paragraph (a) of this section.

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(c) Engine on a bed. If the engine sits on a bed located on the vessel's bottom timbers, take depths when measuring the propelling machinery space from the under side of the deck, or line of same down to the top of the bottom frames or floor timbers as the case may be, or to the ceiling thereon when fitted.

(d) Boxed-in engine. (1) When the portion of the engine extending above a cockpit platform is boxed in such boxedin portion is considered to be all of the space available for the installation and operation of the engine above the line of said platform in that part of the vessel.

(2) In the case of a wholly boxed-in engine in the hold of a motorboat, the tonnage of the boxed-in space, plus the shaft, engine auxiliaries, etc., that may be outside the boxing is considered the propelling machinery space.

(3) The above restrictions may invalidate light and air exemption when the boxing does not extend above the line of the upper deck. However, when such boxing does extend above said deck line, the height of light and air exemption is from the upper deck line to the under side of the top of the boxing.

§2.58 Deduction for propelling power.

In the case of a vessel propelled by steam or other power, a deduction shall be made for the propelling machinery space according to the percentage ratio between the actual tonnage of such space and the vessel's gross tonnage, calculated as follows:

For vessels propelled by screw in whole or in part:

13 percent or less: Deduct 32/13 times the tonnage of the actual propelling machinery space; or, in the case of a vessel the construction of which was commenced on or before June 4, 1956, if the owner so elects, deduct 14 times the tonnage of the actual propelling machinery space.

Above 13 percent, below 20 percent: Deduct 32 percent of the gross tonnage.

20 percent or more: Deduct 32 percent of the gross tonnage or 14 times the tonnage of the actual propelling machinery space, whichever the owner elects.

For vessels propelled by paddle-wheel in whole or in part:

20 percent or less: Deduct 37/20 times the tonnage of the actual propelling machinery space; or, in the case of a vessel the construction of which was commenced on or before June 4, 1956, if the owner so elects, deduct 11⁄2 times the tonnage of the actual propelling machinery space.

Above 20 percent, below 30 percent: Deduct 37 percent of the gross tonnage.

30 percent or more: Deduct 37 percent of the gross tonnage or 11⁄2 times the tonnage of the actual propelling machinery space, whichever the owner elects.

§ 2.59 Light and air spaces.

(a) Application for allowance. On a request in writing by the owner of a vessel to the collector of customs of the district in which the vessel is located, the tonnage of such portion of the space or spaces above the crown of the engine room and above the line of the upper deck as is framed in for the machinery, or for the admission of light and air, and not required to be included in the gross tonnage, shall for the purpose of ascertaining the tonnage of the space occupied by the propelling machinery, be added to the said machinery space; but it shall then be included in the gross tonnage. Such space or spaces must be reasonable in extent, safe, and seaworthy and cannot be used for any purpose other than the machinery or for the admission of light and air to the propelling machinery space of the vessel.

(b) Reasonable in extent. In construing the words "reasonable in extent" the measurer should note that the length should not exceed the length of the propelling machinery space, and if any portion is plated over, the length of such part must be deducted from the full length and whatever the breadth of the casing may be, the breadth allowed must not exceed one-half the extreme inside midship breadth of the vessel.

(c) Purpose for including light and air spaces. The purpose of adding a part of the framed-in light and air spaces (above the crown of the boiler and engine room and above the upper deck) of a vessel to her machinery space below the upper deck is to entitle the vessel to a greater deduction for propelling power, and consequently obtain a smaller net tonnage than would otherwise result. To get this benefit, it does not always require the addition of the total of such light and air spaces. such cases only such portion need be added as hereinafter explained.

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(d) Rule for computing addible light and air space. Below is given a simple rule for finding the amount of light and

air space or spaces required to be added to the gross tonnage and also to the propelling machinery space of a mechanically propelled vessel to entitle her to 32 percent of her gross tonnage for propelling-power deduction when granted by the collector upon request of her

owner or owners:

Find 13.1 percent of the gross tonnage inclusive of excess hatchways. Find the difference between this percent and the tonnage of the propelling machinery space below the upper deck to the hull. Increase this difference by 15 percent of itself, which gives approximately the amount of light and air space or spaces to be added to the gross tonnage defined above, and also to the propelling machinery space below said upper deck. The gross register tonnage in such a case is the gross tonnage as defined above, plus light and air addition, less one-half of 1 percent of said light and air addition, which one-half percent is additional allowance for excess hatchways due to addition of light and air to gross tonnage. EXAMPLE

Gross tonnage, exclusive of light and air and hatchways-‒‒‒‒‒ Excess of hatchways (based on the above)

5,675.95

67.37

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§ 2.60 Verification of calculations, diagram of areas, and certification of results.

(a) Calculations to be verified and diagram of areas made. Calculations must be verified at least twice and a diagram of half breadths for areas made. (See Figures 52 and 53 (§ 2.65).)

(b) Certification of results. The deductions having been made from the gross tonnage and the remainder or net tonnage having been properly marked on the main beam, the surveyor or measuring officer will certify the result to the collector on Form 1322.

§ 2.60a Marking net tonnage and official number on vessel.

(a) The official number of a vessel, preceded by the abbreviation "NO.", and the net tonnage, preceded by the word "NET", shall be marked in a conspicuous place on her main beam at the expense of the owner or master, in Arabic numerals of the block type at least three inches in height, when the size of the main beam will permit. If the main beam is of wood, it shall be carved or branded in figures not less than threeeighths of an inch in depth. If the main beam is of iron or other metal, the official number and net tonnage shall be outlined by punch marks and painted over with oil paint in a light color on a dark background or a dark color on a light background.

(b) The beam at the forward end of the largest hatch on the weather deck which is generally located forward of amidships shall be considered the main beam for the purposes of these regulations. In the case of a vessel which does not have a hatch on the weather deck, any structural member which is integral to the hull may be considered the main beam.

(c) The official number awarded to a vessel shall pertain only to that vessel. If a vessel, having once received an offcial number, is rebuilt or redocumented, the number originally awarded shall be retained.

§ 2.61 Appendix to certificate of registry.

(a) When a vessel of the United States carries passengers to a foreign port or ports the collector of customs will

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