The hull is the entire structure of the ship, which is closed on the side and the top with the outer return, and the top with the top full deck. The boat bolt is a bridge between the ship and the propulsion machine, so it must be selected so that in normal operation, the absorption curve does not fall into the unfavorable operating area of the propulsion machine, ie that it does not break through the driving curve of the propulsion machine. The fundamental and permanent problem in the ship's hydrodynamics is the establishment of a ship that will withstand the minimum resistance to meet the requirements of displacement and speed. Knowing the shape of the flow around the boat and the individual components of resistance is very significant in the development of the ship's shape. Forming is called the difference between the speed of the boat and the speed of the bevel. It is quite understandable that the bolt will affect the flow of water around the boat. When the boat is towed, when the bolt is not in motion, the boat's resistance is higher because of the water flow around the screw. The difference between the theoretical speed and the actual speed of the bolt is slippery.