When the same ship sails in the ocean, why is the draft different in winter and summer?

Ship draft generally refers to the depth at which the ship is immersed in water. It refers to the vertical distance from the bottom of the ship to the place where the hull meets the water surface, which indirectly reflects the buoyancy of the ship during the journey (or the weight of the hull and its cargo, etc., because this is equal to the buoyancy experienced by the hull).

Design draft and structural draft.

The draft of the ship is the design draft and the structural draft, and the structural draft is larger than the design draft.

Design draft: The vertical distance from the lower edge of the flat keel in the middle of the hull to the upper edge of the design waterline.

Structural draft: the vertical distance from the lower edge of the flat keel in the middle of the hull to the ship's summer load line.

The reason why the design draft and structural draft of the ship are set up is that two major calculations need to be carried out when the ship is designed, namely stability calculation and structural calculation, the former ensures the stability and safety of the ship during operation, and the latter ensures the structural safety of the ship during operation.

There needs to be a standard when calculating stability, and the full-load draft at this time is set as the design draft, and the speed is assessed in the draft state, which is used as a working condition for accounting stability. But sometimes the ship is loaded with high-density goods, such as steel plates, the center of gravity of the cargo is very low, even if it is loaded, it is safe to exceed the design draft in terms of stability, so there is a new saying, heavy load, but the next problem is that although the stability is no problem when heavy load, the structure calculated according to the design draft is not safe when it is overloaded, so a structural draft (greater than the design draft) is defined at the beginning of the ship's design, and the structure is calculated according to the structural draft. In this way, even if the heavy load exceeds the design draft during operation in the future, as long as the structural draft is not exceeded, the ship is safe.

There is also a purpose for setting up a structural draft, leaving room for future ship modifications, after all, marine equipment can be replaced at any time, and the hull structure is to accompany the entire life of the ship.

When the weather is hot, the density of the sea becomes smaller; When the weather is cold, the density of the sea increases, so the draft of the same ship is smaller in winter than in summer. Moreover, fresh water or salt water will have an impact on the draft of the ship.

When the weather is hot, the density of the sea becomes smaller; When the weather is cold, the density of the sea increases. So the draught of the same ship is smaller in winter than in summer.

Knowledge points: When the weather is hot, the density of seawater becomes smaller; When the weather is cold, the density of the sea increases, so the draft of the same ship is smaller in winter than in summer.

The temperature of the sea water is different, so the density of the sea water is not the same, so the draft is not the same.

Because of the difference in density and temperature, the depth is not the same.

Because of different temperatures, the density of seawater is not the same.

Because when the temperature of the water is high, the relative density is small.

The temperature does not have to be caused, and the density of water is different than that of Rong.

When the weather is hot, the density of the sea becomes smaller;

Because the density of water in winter is not the same as that in summer.

The depth of the ship's draft is smaller in winter than in summer.

So the draught of the same ship is smaller in winter than in summer.

The sea is very large and has currents, and the addition of ocean currents under the action of the sun will cause different salinity of currents in different areas, which means different densities, so that ships of the same tonnage will have different drafts in different densities.

According to the literature on ships, displacement is related to the season (summer and winter), and draft is the specific embodiment of displacement.

In general, the water depth of the river on a recorded route must be 3-8 meters greater than the maximum draft of the vessel in order to be able to navigate safely. The longitudinal shaking of the ship caused by the wind direction or waves will inevitably cause the local depth of the hull to be greater than the draft.

And the absolute depth of the water level is not static, and the rocks, wrecks, etc. at the bottom of the water can also affect navigation.

The exact figure is determined by the length and type of vessel, the specific hydrological conditions and the meteorological environment.