(7) "Permeability" of a space is the percentage of that space (volume) which can be occupied by water.

(8) "Machinery Space" is to be taken as extending from the top of the keel to the margin line, and between the extreme main transverse watertight bulkheads bounding the spaces devoted to main and auxiliary propelling machinery, boilers when installed, and all permanent coal bunkers.

(9) "Passenger Spaces" are those which are provided for the accommodation and use of passengers, excluding baggage, store, provision and mail rooms. Spaces provided below the margin line, for the accommodation and use of the crew, shall be regarded as passenger spaces for the purpose of estimating permeability (Reg. III), and determining the criterion of service numeral (Reg. IV). Further for the purpose of estimating permeability (Reg. III), if any between-deck compartment between two watertight transverse bulkheads contains any passenger or crew space, the whole of that compartment, less any space completely enclosed within permanent steel bulkheads and appropriated to other purposes, shall be regarded as passenger space. If, however, the passenger or crew space in question is completely enclosed within permanent steel bulkheads, only the space so inclosed need be considered as passenger space (p. 38, p. 32, p. 39, Reg. III, par. 4).

"Completely inclosed within permanent steel bulkheads" is taken to mean watertight bulkheads without doors or other openings.

(10) "Volumes" in all cases are to be calculated to molded lines.

This

(11) The "Floodable Length" at any point is the maximum portion of the length, with its center at the point which can be flooded under the assumption as to permeability (Reg. III), without the ship being submerged beyond the margin line. definition assumes a continuous bulkhead deck. For a ship that does not have a continuous bulkhead deck, the floodable length is calculated for an assumed continuous margin line, up to which, having regard to sinkage and trim after damage, the sides of the ship and the bulkheads concerned are carried watertight (p. 37, p. 31, p. 38, Reg. II, paragraphs 2 and 3).

Floodable Length.

31. The floodable length at any point of the length of the ship shall be determined by a method of calculation which takes into consideration the form, draft, and other characteristics of the ship in question (p. 36, p. 31, p. 38, Reg. II, par. 1).

This includes the short method recommended by the Bulkhead Committee and promulgated by the British Board of Trade, also any direct method that takes account of the characteristics of the ship as stated and gives substantially accurate results.

Permeability.

32. In determining the floodable length, a uniform average permeability shall be used throughout the whole length of each of the following portions of the ship below the margin line:

(a) The machinery space (see definition, par. 30 of this statement).

(b) The portion forward of the machinery space.

(c) The portion abaft the machinery space.

Machinery Space Permeability.

33. The following rule for determining the uniform average permeability for the machinery space of steamers takes the place of the requirements of the former Convention. For most vessels it results in a small increase of the permeability percentage.

Machinery space permeability percent

Where A

C

V

=

=

=

=

80+ 12.5

(AC)

Volume of passenger spaces (see definition, par. 30 of this statement) below the margin line and within the machinery space.

Volume of between-deck spaces below the margin line, and within the limits of the machinery space, which are appropriated to cargo, coal or stores. Whole volume of machinery space below the margin line (whole molded volume below margin line and between the main transverse watertight bulkheads that bound the machinery spaces).

For ships propelled by internal combustion engines the uniform average permeability percentage shall be taken as 5 greater than that given by the above formula.

Where it is shown to the satisfaction of the Administration that the average permeability (of the machinery space), as determined by detail calculation, is less than that given by the formula, the calculated values may be substituted. For the purpose of such calculation permeabilities shall be taken as follows: (a) Passenger spaces (see definition, par. 30 of

this statement)

98 per cent

60 per cent

(b) Cargo, coal and store spaces. (c) Double bottom tanks, oil fuel tanks and other tanks at values approved in each case by the Administration (p. 37, p. 32, p. 38, Reg. III, par. 2).

Previous practice has been to take peaks, also double bottoms, when used for ballast tanks, fresh water tanks, fuel oil tanks, or when kept empty, at 95 per cent permeability. Fuel oil tanks and water tanks above the inner bottom have been taken at 60 per cent permeability.

Permeability Forward (or Abaft) the Machinery Space.

34. The following rule governs for the uniform average permeability percentage to be used for the portion of the ship below the margin line and forward (or abaft) the machinery space. This rule maintains the principle of the corresponding requirements of the former Convention.

Space forward (or abaft) the

=

machinery space, permeability per cent 63 +35

Where A

=

Volume of passenger spaces (see definition, par. 30 of this statement) below the margin line and before (or abaft) the machinery space.

V = Whole volume of the portion of the ship below the margin line, and before (or abaft) the machinery space (p. 38, p. 32, p. 39, Reg. III, par. 3). Compartments' Permissible Length; Factor of Subdivision.

35. The maximum permissible length of a compartment having its center at any point in the ship's length is obtained by multiplying the floodable length at that point by an appropriate factor called the Factor of Subdivision (p. 38, p. 33, p. 39, Reg. IV).

The factor of subdivision is unity for the lowest standard of subdivision, and is a faction decreasing in numerical value as the standard of subdivision becomes higher. The value of the factor of subdivision depends on the length of the ship, and, for a ship of given length, upon the nature of the service for which the ship is intended. The "nature of the service" is assessed by a Criterion of Service Numeral (see paragraphs 23 and 36 of this statement).

The factor of subdivision decreases as the length of the ship increases; the relation is given by the following formulae:

In the above formulae, A is the factor of subdivision for the lower standard and for the same length of ship has a greater numerical value than B, the factor of subdivision for the higher standard. L is the length of the ship (see definition, par. 30 of this statement) in feet. Formula for A applies to ships 430 feet long and upwards; formula for B to ships 260 feet long and upwards (p. 38, p. 33, p. 39, Reg. IV, par. 1).

Criterion Numeral.

36. For a ship of given length the appropriate factor of subdivision shall be determined by the Criterion of Service Numeral, called the "Criterion Numeral," as given by formula (iii) or (iv).

L

=

Length of ship (see definition, par. 30 of this statement).

M = Volume of machinery space (see definition, par. 30 of this statement), plus the volume of any permanent oil fuel bunkers above the inner bottom and before or abaft the machinery space.

=

P The whole volume of passenger spaces (see definition, par. 30 of this statement) below the margin line.

P1 = K N where N is the number of passengers for which the ship is to be certified, and K is sixtenths of the length in feet, so that P1 = .6 L N.

Where the value of K N is greater than the sum of P and the whole volume of actual passenger spaces above the margin line, this sum may be used in place of K N provided that it is not less than 23 K N.

Formula (iii) is used when the value of P1 is greater than P, and formula (iv) is used in other cases.

For ships not having a continuous bulkhead deck, the volumes are to be taken up to the assumed continuous margin line used in determining the floodable length. See definition 11, par. 30. of this statement (p. 39, p. 33, p. 40, Reg. IV, par. 2).

RULES FOR SUBDIVISION

Subdivision of Ships 430 Feet Long and Upwards.

37. The subdivision abaft the fore peak of ships 430 feet in length and upwards shall be determined as follows:

Those having a criterion numeral of 23 or less shall be governed by the factor "A" given by formula (i), paragraph 35.

Those having a criterion numeral of 123 or more shall be governed by the factor "B" given by formula (ii), paragraph 35.

Those having a criterion numeral between 23 and 123 shall be governed by a factor "F," obtained by linear interpolation between the factors "A" and "B," using the formula:

Where Cs is the criterion numeral with a value between 23 and 123.

Where the factor "F" is less than .40 and it is shown to the satisfaction of the Administration to be impracticable to comply with the factor "F" in a machinery compartment of a ship, the length of such compartment may be governed by an increased factor, which, however, shall not exceed .40 (p. 39, p. 34, p. 41, Reg. IV, par. 3).

In ships 430 feet in length and upwards, one of the main transverse bulkheads abaft the fore peak shall be fitted at a distance from the forward perpendicular which is not greater than the permissible length (p. 41, p. 34, p. 42, Reg. V, par. 2).

Subdivision of Ships 260 Feet to 430 Feet Long.

38. The subdivision abaft the fore peak of ships less than 430 feet, but not less than 260 feet in length, shall be determined as follows:

S

Those having a criterion numeral equal to "S" where 9382-20 L

for L in feet, shall be governed by the factor unity.

Those having a criterion numeral of 123 or more shall be governed by the factor "B" given by formula (ii), paragraph 35.

Those having a criterion numeral between "S" and 123 shall be governed by a factor "F," obtained by linear inter