A long box shaped hydraulic structure built on the shore of a water area for repairing and shipbuilding is conventionally called a dock. The dock bottom is lower than the water surface, three sides are dock wall, connected with the shore, one side has dock mouth leading to water area, and has dock door. The dock was originally mainly used for repairing ships. With the development of large-scale ships, it is safer and more advantageous for ships of more than 100000 tons to be built in docks. Therefore, docks are also used for shipbuilding and are developing to large-scale. The traditional method of building a dock is to build a cofferdam in the water near the bank, drain the water in the dam, and then excavate the foundation pit for dry construction. If the dock is built in the harbor basin, or the foundation is sandy soil with great permeability or there are river sea cracks
Buoyancy Law: the object immersed in the liquid is subject to upward buoyancy, and the buoyancy is equal to the gravity of the object to displace the liquid. In other words, f float = g row = m row g = ρ liquid GV row g row: gravity of draining liquid m row: discharging liquid mass ρ liquid: liquid density V row: volume of liquid discharged (i.e. volume immersed in liquid). If it is a solid iron block, it must sink. Because the ship's interior is empty, so the ship's displacement in the water will be large, When the gravity of the drained water is equal to the weight of the ship, the ship floats. This is a matter of buoyancy, because the density of steel is greater than that of water
The main engine power of the power plant fishing boat is generally 1.5 ~ 4.5 kW / T, some as high as 6 ~ 7 kW. Large and medium-sized fishing vessels and fishing base vessels are equipped with freezing and processing equipment, and the engine power is 65% - 85% of the main engine power. In order to improve the efficiency of the main engine, the engine, capture winch, refrigeration device and air compressor are often driven by the main engine, which increases the complexity of the power plant. The working conditions of trawlers, fishing inquiry vessels and longline fishing vessels are changeable. Adjustable pitch propeller and booster are often used to make rational use of the main engine power and improve the ship's performance
The basic framework structure of fishing vessels is the main framework structure of fishing vessels. The longitudinal skeleton plate has a long edge, a long length direction, a short edge width direction, and a small distance between longitudinal bones and a large distance between transverse girders. In the direction of long edge ship width and short edge length, the distance between transverse stiffeners is small and that of longitudinal girders is large. According to the strength and application requirements, the combination of longitudinal frame and transverse frame can be selected for some structures of ships. For example, longitudinal frame is selected for upper deck and bottom of some large cargo ships to increase the total longitudinal strength of the hull
Rafts and canoes in the early primitive society, the primitive ancestors lived on fishing, hunting and catching, and their activities were limited to areas close to the water. They needed something urgently to get more food and resist the damage of flood. Later, the ancients thought of the fallen leaves as a boat and saw the floating wood as a boat, and invented the water transportation East-West raft, also known as the "Luo" and "Xiao". After weaving wooden rafts, there were also wooden canoes and Shanmu boats. The spring and Autumn period and the Warring States Period - in the Shang Dynasty, the ancient people were no longer limited by the shape and size of wood, but could be processed according to the data. In this way, the wooden boat appeared.
FRP is a new shipbuilding material and an important part of modern material innovation. FRP has not been used in shipbuilding for a long time, but it has shown its strong vitality and broad development prospects. FRP ships include not only small boats, such as fishing boats, yachts, high-speed passenger ships, business boats, traffic boats, speedboats, lifeboats, painted boats, sailboats, sports boats, minesweepers, etc. Careful preservation and maintenance of fishing vessels can reduce the loss and extend the service life of fishing vessels. Now many fishing boats use FRP materials. Let's take FRP fishing boats as an example to share the maintenance secrets. Glass fiber reinforced plastics (FRP) is a kind of
1. Corrosion of the hull structure on the water, the part on the water of the hull mainly includes the deck, superstructure and freeboard. The above water parts of these ships are mainly affected by rain and snow, sea water spray and ocean atmosphere, and these factors are the important reasons for the severe corrosion of the hull on water. In the marine atmosphere, there are a lot of nitrogen compounds, which make the condensation water aggravate the damage to the hull structure. On the other hand, the high temperature of the engine room and boiler in the deck also aggravates the water damage in these areas to a certain extent. Some scientific experiments have shown that,
We know that the sea water has strong corrosivity to the ship, and the marine life has strong adhesion to the ship. After the ship is launched for a period of time, a lot of barnacles, algae and other marine organisms will be attached to the hull, and rust spots will appear. On the other hand, the presence of these warships increases the speed of the ship's flight and, on the other hand, increases the resistance of the ship's flight. Marine attached organisms refer to the animals, plants and microorganisms that grow on the bottom of the ship and on the surface of the equipment in the sea. Microappendages include bacteria, diatoms, protozoa (unicellular animals), rotifers and