Introduction to R & P

Resistance and Propulsion of Ships Preliminary propeller design using charts

Introduction to R & P

! Example 3

Resistance and Propulsion of Ships

Fishing vessel Use the K-J chart to select the appropriate P/D ratio for a B4-70 screw to be used for this vessel. Estimate open water efficiency.

Introduction to R & P

! Example 3

Resistance and Propulsion of Ships

J = 0.36 KT = 0.131 Find this on the chart… …it lies on the KT curve for a prop with a P/D of 0.6. Find the corresponding KQ for P/D = 0.6. KQ = 0.0155

KT=0.131

10KQ=0.155

Introduction to R & P

! Example 3

Resistance and Propulsion of Ships

This chart may be easier to use…

KT=0.131

P/D (KT) = 0.60 P/D (KQ) = 0.60

10KQ=0.155

Introduction to R & P

! Example 4

Resistance and Propulsion of Ships

Harbor tug Use the µ-σ chart to select the appropriate P/D ratio for a B4-70 screw to be used for this vessel. Estimate open water efficiency.

Introduction to R & P

! Example 4

Resistance and Propulsion of Ships

µ = 5.19

φ = 2.10

Go to chart and find µ = 5.19.

µ = 5.19

Introduction to R & P

! Example 4

Resistance and Propulsion of Ships

µ = 5.19

φ = 2.10

Go to chart and find µ = 5.19.

Track along φ =2 and then estimate (interpolate) the point on the line for µ = 5.19 and φ =2.1.

µ = 5.19

φ = 2.10

Introduction to R & P

! Example 4

Resistance and Propulsion of Ships

µ = 5.19

φ = 2.10

µ = 5.19

φ = 2.10

Go to chart and find µ = 5.19.

Track along φ =2 and then estimate (interpolate) the point on the line for µ = 5.19 and φ =2.1. Read the P/D ratio as approximately 0.92. (Interpolation is required).

P/D = 0.92

Introduction to R & P

! Example 4

Resistance and Propulsion of Ships

µ = 5.19

φ = 2.10

µ = 5.19

φ = 2.10

Go to chart and find µ = 5.19.

Track along φ =2 and then estimate (interpolate) the point on the line for µ = 5.19 and φ =2.1. Read the P/D ratio as approximately 0.92. (Interpolation is required). Note also that ηo = 0.44 and σ = 1.1

P/D = 0.92

σ = 1.1

ηο = 0.44