Marine Engineering

The frictional resistance R🇫 of the hull depends on the size of the hull’s wetted area AS, and on the specific frictional resistance coefficient CF. The friction increases with fouling of the hull, i.e. by the growth of, i.a. algae, seagrass, and barnacles. An attempt to avoid fouling is made by the use of antifouling hull paints to prevent the hull from becoming “longhaired”, i.e. these paints reduce the possibility of the hull becoming fouled by living organisms. The paints containing TBT (tributyltin) as their principal biocide, which is very toxic, have dominated the market for decades, but the IMO ban of TBT for new applications from 1 January 2003, and a full ban from 1 January 2008, may involve the use of new (and maybe not as effective) alternatives, probably copper-based antifouling paints. When the ship is propelled through the water, the frictional resistance increases at a rate that is virtually equal to the square of the vessel’s speed. Frictional resistance rep...

To move a ship, it is first necessary to overcome resistance, i.e. the force working against its propulsion. The calculation of this resistance, R plays a significant role in the selection of the correct propeller and in the subsequent choice of main engine. A ship’s resistance is particularly influenced by its speed, displacement, and hull form. The total resistance Rт consists of many source resistances R which can be divided into three main groups: 1) Frictional resistance 2) Residual resistance 3) Air resistance The influence of frictional and residual resistances depends on how much of the hull is below the waterline, while the influence of air resistance depends on how much of the ship is above the waterline. In view of this, air resistance will have a certain effect on container ships which carry a large number of containers on the deck. Water with a speed of V and a density of ρ has a dynamic pressure of: ½ ×   ρ × V 2 (Bernoulli’s law) Thus, if water is bei...