1. Chapter 9
Form coefficients

2. The coefficient of fineness of the water-plane area (Cw)
It is the ratio of the area of the water-plane to the area of a rectangle having the same length and maximum breadth.

3. Coefficient of fineness (Cw )
Area of water-plane Coefficient of fineness (Cw ) = Area of rectangle ABCD = L x B Area of the water-plane = L x B x Cw

4. Coefficient of fineness (Cw )

5. Coefficient of fineness (Cw )

6. The block coefficient of fineness of displacement (Cb)
The block coefficient of a ship at any particular draft is the ratio of the volume of displacement at that draft to the volume of a rectangular block having the same overall length, breadth and depth.

7. The block coefficient of fineness of displacement (Cb)
Volume of displacement Block coefficient (Cb)= Volume of the block = L x B x draft Volume of displacement = L x B x draft x Cb

8. Ship’s lifeboats
The accepted Cb for a ship’s lifeboat constructed of wooden planks is 0.6 and this is the figure to be used in calculations unless another specific value is given
Volume = (L x B x Depth x 0.6) cubic metres

9. The block coefficient of fineness of displacement (Cb)

10. The block coefficient of fineness of displacement (Cb)

11. The midships coefficient (Cm)
The midships coefficient to any draft is the ratio of the transverse area of the midships section (Am) to a rectangle having the same breadth and depths.

12. The midships coefficient (Cm)
Midships area (Am) Midships coefficient (Cm) = Area of rectangle = B x d Midships area (Am) = L x B x Cm

13. The prismatic coefficient (Cp)
The prismatic coefficient of a ship at any draft is the ratio of the volume of displacement at that draft to the volume of a prism having the same length as the ship and the same cross-sectional area as the ship’s midships area.

14. The prismatic coefficient (Cp)
Volume of ship Prismatic coefficient (Cp) = Volume of prism = L x Am Volume of ship = L x Am x Cp

15. The relation between coefficients
Am Volume of ship
Cm x Cp = x
B x d L x Am
Volume of ship =
L x B x d
Cm x Cp = Cb