Page 83 - Introduction to Naval Architecture

70 FLOTATION AND STABILITY

Table 4.3

Inclination GZ Simpson 's Area
o m multiplier product

0 0 1 0
15 0.203 4 0,812
30 0.540 2 1.080
45 0.835 4 3.340
60 0.692 1 0.692
Summation = 5.924

Influence of wind on stability
In a beam wind the force generated on the above water surface of tJhe
ship is resisted by the hydrodynamic force produced by the slow sideways
movement of the ship through the water. The wind force may be taken to
act through the centroid of the above water area and the hydrodynamic
force as acting at half draught, Figure 4.31. For ships with high freeboard
the variation of wind speed with height may be worth allowing for (see
Chapter 5). For all practical purposes the two forces can be assumed
equal.
Let the vertical distance between the lines of action of the two
forces be h and the projected area of the above water form be A, To
a first order as the ship heels, both h and A will be reduced in
proportion to cos <p.

Figure 431 Heeling due to wind