What is effect of wind on Ship Manoeuvring or Motion ?

The wind-force can be calculated with the   formula:

wind-force = 0.004 x W x  v² 

 where: W = windage in square feet

             v = wind speed in knots wind-force is expressed in pounds

Wind speed as well as wind direction, ship’s speed, and ship’s heading are not at all times constant during the maneuver. A slight error in wind speed is of much greater consequence than a similar error in assumed windage of the tanker. The following approximations for assumed windage will therefore be good enough for our purpose.

W (abeam) = LOA x D – LBP x mean draft

W (on the bow ) = В x D – В x draft forward

where: LOA = length overall

           LBP = length between perpendiculars

          В = breadth, molded

         D = depth, molded

For intermediate angles we take the median between the direct proportional value and the value proportional to the sine of the angle of incidence.

On the following pages we will examine the effect of a 25-knot wind on a 70,000-dwt tanker in ballast; draft 16 feet forward and 26 feet aft; LOA = 800 feet; LBP = 765 feet; В = 115 feet; D = 56 ft; engine power = 20,000 HP; and stern power = 16,000 HP.