The article describes what a waterline is, why it is needed, and when the law on the mandatory use of one of its varieties was first introduced.
Ships
For a very long time, the only and relatively fast way to travel was ships. Of course, their use entailed a number of limitations, but there were simply no more convenient and safer alternatives.
Over time, when more or less reliable navigation devices were invented, people were able to travel between continents, which was a real breakthrough. Gradually, when shipbuilders were able to improve the design of the ships, the marks of the waterline began to appear on them without fail. But what is a waterline and why is it needed? This is what we will understand in this article.
Definition
This word comes from the Dutch language, which is quite logical. After all, it was this kingdom that was one of the first, which was distinguished by the high quality of its fleet.
A waterline is a line along which a calm surface of water comes into contact with the hull of a ship or other floating vessel. If we consider this term from the point of view of designing ships, then the waterline is a section of the hull with a horizontal plane in the drawing. So now we know what the waterline is.
Types of Waterlines
The waterline is of the following types:
- Constructive is a line that is taken as a basis for constructing a theoretical drawing. Based on preliminary calculations, it shows various types of ship displacement.
- The cargo waterline is designed to determine the maximum allowable drawdown due to its workload. Usually, such a ship's waterline coincides with the structural one.
- Estimated shows the draft, which determines the theoretical characteristics of the vessel.
- The current one is not applied to the hull of the vessel, it is a concept that determines the current level of subsidence of the ship depending on its load or type of water.
If we talk about the current waterline, then it is determined depending on many factors, for example, the shape of the hull of the vessel, the density of the material from which it is built, weight, water waves, etc.
The waterline area can be used to calculate the body fullness coefficient. However, depending on the load, weather, water density and other factors, the area of the waterline can vary greatly, and with it the roll and stability of the vessel. If we talk about its length, then it serves as a linear size in determining the Froude number for ships with a displacement, and hence their speed in theory. Now we know what the waterline is.
However, in more detail we will analyze such a variety as a freight brand.
Freight mark
In 1890, a similar mark became mandatory on all cargo ships. Unlike other varieties of the waterline, its purpose has a more practical role.
The fact is that before the introduction of such a waterline, many merchant ships sank due to overload, the difference in water density affected, depending on the region, season, salinity and other things. Then the cargo waterline was introduced. With its help, the person responsible for loading calculates the maximum allowable load on the vessel, checking the route, weather conditions, type of water and other parameters. An example of such marks can be seen in the photo below.
Simply put, a freight mark was introduced in order to monitor the workload of the vessel, and if the water is below the waterline, then everything is in order. But as already mentioned, it depends on the type of water, seasons and other parameters. In 1890, a law was adopted in Britain on the mandatory use of the mark.