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Propeller Blade Thickness : Fixed Pitch Propellers
[Marine Vessel Rules 4-3-3/5.1] [Steel Vessel Rules 4-3-3/5.1]
Unit
Input data
Section modulus coefficient at 0.25 radius (Cn) Click to go calculate setion modulus and section area
Section area coefficient at 0.25 radius (Cs)
Power at rated speed (H)
Number of blades (N)
RPM at rated speed (R)
Expanded area ratio (expanded blade area divided by the disc area) (a)
Diameter of propeller(D)
Maximum design blade thickness at 0.25 radius
Rake at tip of blade (K)
Rake type
Input form of the following two pitch factors
    Pitch at 0.25 radius [P0.25]
    Pitch at 0.70 radius [P0.70]
Expanded width of cylindrical section at 0.25 radius (W0.25)
Material type
Constant w based on material type and unit (w)
Constant f based on material type and unit (f)
Constant K1 based on calculation unit (K1)
Results
Minimum required blade thickness (t0.25) =  
Maximum design blade thickness
 
References
Intermediate Values
A = B =
C = Factor (S) =
Propeller blades of thrusters and wide-tip blades of ducted propellers are to be in accordance with the provisions of Thrusters. The thickness of the propeller blades of conventional design (q <= 25º) is not to be less than that determined by the specified equations.

where (units of measures are given in SI (MKS, and US) units respectively):

Fixed Pitch Propeller Calculation Rule
  • a = expanded blade area divided by the disc area
  • as = area of expanded cylindrical section at 0.25 radius, as applicable; mm2 (mm2, in2)
  • Cn = section modulus coefficient at 0.25 radius, as applicable; to be determined by the specified equation:
    If the value of Cn exceeds 0.1, the required thickness is to be computed with Cn = 0.1.
  • Cs = section area coefficient at 0.25 radius, as applicable, to be determined by the specified equation.
    The values of Cs and Cn computed as stipulated above are to be indicated on the propeller drawing.
  • D = propeller diameter; m (m, ft)
  • f, w = material constants, click on Material tag in the input form to see data table
  • H = power at rated speed; kW (PS, hp)
  • Io = moment of inertia of the expanded cylindrical section at 0.25 radius about a straight line through the center of gravity parallel to the pitch line or to the nose-tail line; mm4 (mm4, in4)
  • K = rake of propeller blade (mm, in.); positive for aft rake, negative for forward rake.
  • N = number of blades
  • You have an option to input the two following fields in ratio of pitch radius divided by propeller diameter or in pitch radius directly, in the later case program will convert the pitch radius to ratio before calculation.
    P0.25 = pitch at 0.25 radius or pitch at 0.25 radius divided by propeller diameter
    P0.7 = pitch at 0.7 radius or pitch at 0.7 radius divided by propeller diameter, corresponding to the design ahead condition
  • R = rpm at rated speed
  • S = factor, from specified equation. If greater than 1.025, equate to 1.025.
  • T = maximum design thickness at 0.25 radius from propeller drawing; mm (mm, in)
  • t0.25 = required thickness of blade section at 0.25 of propeller radius; mm (mm, in)
  • Uf = maximum normal distance from the moment of inertia axis to points in the face boundary (tension side) of the section; mm (mm, in)
  • W = expanded width of a cylindrical section at the 0.25 radius; mm (mm, in)
imgRake Rake is the distance at the blade tip between the generating line and the line perpendicular to the propeller axis that meets the generating line at the propeller axis.