Unless otherwise provided, reference to diameter of propeller shaft in this subparagraph shall mean the diameter of the propeller shaft as provided for the ship.

The length of the boss is to be not less than 4 times the diameter of the propeller shaft. Boss length shall be sufficient to fully support the shaft bearing.

The thickness of the boss is to be not less than one quarter of the diameter of the propeller shaft or as calculated using the formula below.

Where—

• t _boss = required minimum thickness of boss, in millimetres;
• dp = required diameter of propeller shaft (calculated in accordance with subparagraph 9.14.3), in millimetres;
• UTS _shaft = ultimate tensile strength of shaft material, in megapascals (MPa); and
• UTS _bracket = ultimate tensile strength of bracket material, in megapascals (MPa).

Refer to Figure 9(a)

• 9.19.4.1Included angle between legs

  The included angle between the legs shall not be less than 45°.

  NOTES:

  • 1.Bracket leg angle should be carefully selected to prevent interaction between propeller blades and bracket legs. Aerofoil paragraphs require special attention.
  • 2.The scantlings for V-brackets derived from the deemed to satisfy regulation in this part are based on legs having an included angle not less than 45°.
• 9.19.4.2Calculated width

  The calculated width of each solid streamlined leg shall be obtained from the following formula—

  

  Where—

  • W = calculated width of leg (major axis), in millimetres;
  • dp = required diameter of propeller shaft (calculated in accordance with subparagraph 9.14.3), in millimetres;
  • UTS _shaft = ultimate tensile strength of shaft material, in megapascals (MPa); and
  • UTS _leg = ultimate tensile strength of leg material, in megapascals (MPa).
• 9.19.4.3Calculated thickness

  The calculated thickness of each solid streamlined leg shall be obtained from the following formula—

  

  Where—

  • t = calculated thickness of leg (minor axis), in millimetres;
  • dp = required diameter of propeller shaft (calculated in accordance with paragraph 9.14.3), in millimetres;
  • UTS _shaft = ultimate tensile strength of shaft material, in megapascals (MPa); and
  • UTS _leg = ultimate tensile strength of leg material in megapascals (MPa).

Refer to Figure 9(b)

Figure 9 — Propeller Shaft Brackets

• 9.19.5.1Calculated width

  The calculated width of the single solid streamlined leg shall be obtained from the following formula—

  

  Where—

  • W1 = calculated width of leg (major axis), in millimetres;
  • dp = required diameter of propeller shaft (calculated in accordance with subparagraph 9.14.3), in millimetres;
  • UTS _shaft = ultimate tensile strength of shaft material, in megapascals (MPa); and
  • UTS _leg = ultimate tensile strength of leg material, in megapascals (MPa).
• 9.19.5.2Calculated thickness

  The calculated thickness of the single solid streamlined leg shall be obtained from whichever of the following formulae is appropriate—

  • (a)Where the leg is a cantilever—
  • (b)Where the lower end of the leg is attached to a shoe piece or skeg that offers lateral support, see subparagraph 9.25.6.7.2 —
    • Where—
    • t = calculated thickness of the leg (minor axis), in millimetres;
    • dp = required diameter of propeller shaft (calculated in accordance with subparagraph 9.14.3), in millimetres;
    • UTS _shaft = ultimate tensile strength of shaft material, in megapascals (MPa); and
    • UTS _leg = ultimate tensile strength of leg material, in megapascals (MPa).

• 9.19.6.1Stiffness

  Where the bracket is a material other than carbon steel, the moment of inertia about the longitudinal axis shall not be less than that determined from the following formula—

  

  Where—

  • I _l = required moment of inertia of the leg about the longitudinal axis, in cm⁴;
  • w = calculated width of leg as determined by subparagraph 9.19.4.2 or 9.19.5.1 as appropriate, in millimetres;
  • t = calculated thickness of leg as determined by subparagraph 9.19.4.3 or 9.19.5.2 as appropriate, in millimetres;
  • UTS _shaft = ultimate tensile strength of shaft material, in megapascals (MPa);
  • UTS _leg = ultimate tensile strength of leg material, in megapascals (MPa); and
  • Eleg = modulus of elasticity of the leg material, in gigapascals (GPa).
• 9.19.6.2Hollow section and non-streamlined brackets

  Where the bracket is a hollow or non-streamlined section, the cross sectional area, inertia and section modulus of the leg about the longitudinal axis shall be maintained. For the purposes of such calculation, the section modulus shall not be less than that determined from the following formula—

  

  Where—

  • Z _l = required section modulus of the leg about the longitudinal axis, in cubic centimetres (cm³);
  • w = calculated width of leg as determined by subparagraph 9.19.4.2 or 9.19.5.1 as appropriate, in millimetres; and
  • t = calculated thickness of leg as determined by subparagraph 9.19.4.3 or 9.19.5.2 as appropriate, in millimetres.

  The area of the leg shall not be less than that determined from the following formula—

  

  Where—

  • A = required area of the leg, in square centimetres (cm²);
  • w = calculated width of leg as determined by subparagraph 9.19.4.2 or 9.19.5.1 as appropriate, in millimetres;
  • t = calculated thickness of leg as determined by subparagraph 9.19.4.3 or 9.19.5.2 as appropriate, in millimetres;
  • UTS _shaft = ultimate tensile strength of shaft material, in megapascals (MPa); and
  • UTS _leg = ultimate tensile strength of leg material, in megapascals (MPa).
• 9.19.6.3Leg length

  The above formulas have been based on a given maximum length for the longer leg of a “V” bracket or the leg of an “I” bracket. The maximum assumed length, measured from the outside perimeter of the boss to the outside of the shell plating, shall be determined from the following formula:

  

  Where—

  • l _max = maximum length of leg, in millimetres, for application of the formulae in subparagraph 9.19.2 to 9.19.3;
  • dp = required diameter of propeller shaft (calculated in accordance with subparagraph 9.14.3), in millimetres; and
  • UTS _shaft = ultimate tensile strength of shaft material, in megapascals (MPa).

  Where the leg length is less than l _max, the paragraph modulus of the leg may be reduced in proportion to the reduced length, provided the paragraph modulus is not less than 0.85 times the required paragraph modulus Z _l.

  NOTE:

  Where the length l _max is exceeded, the scantlings of shaft brackets will need to be considered as an equivalent solution. The width and thickness of the legs or leg would normally increase to compensate for the increased bending loads and reduced buckling strength.