.1 Shifting boards shall have a thickness of not less than 50 mm and shall be fitted grain-tight and where necessary supported by uprights.

.2 The maximum unsupported span for shirting boards of various thicknesses shall be as follows:

Thickness

Maximum
unsupported span

50 mm

2.5 m

60 mm

3.0 m

70 mm

3.5 m

80 mm

4.0 m

If thicknesses greater than these are provided the maxi mum unsupported span will vary directly with the increase in thickness.

.3 The ends of all shifting boards shall be securely housed with 75 mm minimum bearing length.

12.2 Other materials

Divisions formed by using materials other than wood shall have a strength equivalent to the shifting boards required in A12.1.

12.3 Uprights

.1 Steel uprights used to support divisions loaded on both sides shall have a section modulus given by

W = a x W_{1},

Where:

W = section modulus in cubic centimetres;

a = horizontal span between uprights in metres.

The section modulus per metre span W_{1} shall be not less than that given by the formula:

W_{1} = 14.8 x (h_{1} - 1.2) cm^{3}/m,

Where:

h_{1} - is the vertical unsupported span in metres and shall be taken as the maximum value of the distance between any two adjacent stays or between a stay and either end of the upright. Where this distance is less than 2.4 m the respective modulus shall be calculated as if the actual value were 2.4 m.

.2 The moduli of wood uprights shall be determined by multiplying by 12.5 the corresponding moduli for steel uprights. If other materials are used their moduli shall be at least that required for steel increased in proportion to the ratio of the permissible stresses for steel to that of the material used. In such cases attention shall be paid also to the relative rigidity of each up right to ensure that the deflection is not excessive.

.3 The horizontal distance between uprights shall be such that the unsupported spans of the shifting boards do not exceed the maximum span specified in A12.1.3.

12.4 Shores

.1 Wood shores, when used, shall be in a single piece and shall be securely fixed at each end and heeled against the permanent structure of the ship except that they shall not bear directly against the side plating of the ship.

.2 Subject to the provisions of A12.4.3 and A12.4.4, the minimum size of wood shores shall be as follows:

Length of shore
in metres

Rectangular
section
mm

Diameter
circular
section
mm

Not exceeding 3 m

150 x 100

Over 3 m but not exceeding 5 m

150 x 150

Over 5 m but not exceeding 6 m

150 x 150

Over 6 m but not exceeding 7 m

200 x 150

Over 7 m but not exceeding 8 m

200 x 150

Exceeding 8 m

200 x 150

Shores of 7 m or more in length shall be securely bridged at approximately mid-length.

.3 When the horizontal distance between the uprights differs significantly from 4 m the moments of inertia of the shores may be changed in direct proportion.

.4 Where the angle of the shore to the horizontal exceeds 10° the next larger shore to that required by A12.4.2 shall be fitted provided that in no case shall the angle between any shore and the horizontal exceed 45°.

12.5 Stays

Where stays are used to support divisions loaded on both sides, they shall be fitted horizontally or as near thereto as practicable, well secured at each end formed of steel wire rope. The sizes of the wire rope shall be determined assuming that the divisions and upright which the stay supports are uniformly loaded at 4.9 kN/m^{2} . The working load so assumed in the stay shall not exceed one third of its breaking load.

13. DIVISIONS LOADED ON ONE SIDE ONLY

13.1 Loagitudinal divisions

The load (P) in newtons per metre length of the divisions shall be taken as follows: