New Zealand Gazette – 1934 – No. 77

Page 3255

✨ Marine Safety Regulations



Oct. 12.] THE NEW ZEALAND GAZETTE. 3255

Depth to Strength Deck (Ds).—The depth to strength deck is the vertical distance in feet amidships from the top of the keel to the top of the strength deck beam at side.

Draught (d).—The draught is the vertical distance in feet amidships from the top of the keel to the centre of the disc.

Longitudinal Modulus.—The longitudinal modulus I/y is the moment of inertia I of the midship section about the neutral axis divided by the distance y measured from the neutral axis to the top of the strength deck beam at side, calculated in way of openings but without deductions for rivet holes. Areas are measured in square inches and distances in feet.

Below the strength deck, all continuous longitudinal members other than such parts of under deck girders as are required entirely for supporting purposes, are included. Above the strength deck, the gunwale angle bar and the extension of the sheerstrake are the only members included.

The required longitudinal modulus for effective material is expressed by f.d.B., where f is the factor obtained from the following table :—

L. f. L. f.
100 1·80 360 9·40
120 2·00 380 10·30
140 2·35 400 11·20
160 2·70 420 12·15
180 3·15 440 13·10
200 3·60 460 14·15
220 4·20 480 15·15
240 4·80 500 16·25
260 5·45 520 17·35
280 6·20 540 18·45
300 6·95 560 19·60
320 7·70 580 20·80
340 8·55 600 22·00

For intermediate lengths, the value of f is determined by interpolation.

This formula applies where L does not exceed 600 feet; B is between L/10 + 5 and L/10 + 20, both inclusive, and L/Ds is between 10 and 13·5, both inclusive.

Frame.—For the purpose of the frame modulus, the frame is regarded as composed of a frame angle and a reverse angle each of the same size and thickness.

Frame Modulus.—The modulus I/y of the midship frame below the lowest tier of beams is the moment of inertia I of the frame section about the neutral axis divided by the distance y measured from the neutral axis to the extremity of the frame section, calculated without deduction for rivet and bolt holes. The modulus is measured in inch units.

The required frame modulus is expressed by s (d−t) (f₁ + f₂) / 1,000

where—

s is the frame spacing in inches.

t is the vertical distance in feet measured at amidships from the top of the keel to a point midway between the top of the inner bottom at side and the top of the heel bracket (see Figure 2); where there is no double bottom, t is measured to a point midway between the top of the floor at centre and the top of the floor at side.

f₁ is a coefficient depending on H, which, in ships fitted with double bottoms, is the vertical distance in feet from the middle of the beam bracket of the lowest tier of beams at side to a point midway between the top of the inner bottom at side and the top of the heel bracket (see Figure 2). Where there is no double bottom, H is measured to a point midway between the top of the floor at centre and the top of the floor at side. Where the frame obtains additional strength from the form of the ship, due allowance is made in the value of f₁.



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✨ LLM interpretation of page content

🚂 Rules for determining Maximum Load Lines of Merchant Ships (continued from previous page)

🚂 Transport & Communications
Load Lines, Merchant Ships, Marine Safety, Regulations, Depth to Strength Deck, Draught, Longitudinal Modulus, Frame Modulus