Shipbuilding is one of the most complex areas of human activity. There are many different concepts in this area, the meaning of which is known only to professionals. One such term is "stem". This word can also be found in scientific and fiction literature when describing ships.
Meaning of term
The stem is the front, most durable structure in the bow of the ship. It is represented by a steel beam, as well as a forged or cast strip, curved in the shape of the bow of the vessel.
Depending on the conditions in which the ship is operated, what speed and quality it has, the hull is given the appropriate shape. The stem is a kind of continuation of the keel of the vessel. The transition to the keel line can be rounded, smooth or with a break. The shape of the stem creates a general impression of the ship itself. Even visually, a ship can be considered high-speed if it has a protruding stem. A photo of this part of the ship is presented in the article.
Functions
The stem is a part that was used in warships of the old types as a ram against smaller ships. Submarines or destroyers could also perform a similar task. A ship equipped with a heavy stem is able to pierce the outer skin without serious damage to itself: the hole is formed above the waterline.
Modern ships are equipped with bows capable of ramming even submarines made from very thick steel sheets. Since the forward part of the ship's hull is strongly affected by wave impacts, the stems of non-combat ships must also be of very strong construction.
What are stems?
When choosing one or another stem, the purpose of the ship and its shape are taken into account. Shipbuilding uses the following types:
Tilted forward. In the underwater part, the stem at an angle passes into the keel of the ship, which gives the impression of striving forward. Due to such a stem, the lifting of the vessel on the wave improves
- Klipersky. Its shape is similar to an inclined stem. Used in sailing ships.
- The bulbous stem of the boat in the surface part is represented by an inclined or concave line. The line under water has a teardrop shape. They are equipped with ships with a large hull width. Through the use of such a stem, it is possible to achieve a decrease in wave resistance and an increase in travel speed. Since such a stem is highly susceptible to hydrodynamic effects during pitching, it is strengthened with longitudinal and transverse stiffeners.
- Icebreaker. Have suchstem of an ice-class vessel. The line of this stem in the surface part is slightly inclined forward. Closer to the surface of the water, the slope is 30 degrees. The same angle is maintained in the underwater part until the very transition to the keel line. Ships equipped with such stems can easily float on the ice, pushing it with their weight.
Straight. Under water, it has a straight line, which smoothly turns into a keel. This stem is used by river boats with free deck space, which float on calm water surfaces. The straight stem is convenient for viewing the space in front of the bow of the ship in places with constrictions and when approaching berths
Variants
These parts of the ships differ from each other also in design. The following types are used in shipbuilding:
- Square. This design is considered the oldest. Today, tugs and small fishing boats with a bar keel are equipped with such stems. The stems in ice-class ships are equipped with special notches (dowels) into which sheets of outer skin are inserted. This design allows the vessel to remain sealed when damaged.
- Cast. In contrast to the bar stem, the cast shape in cross section easily fits with the waterline. Due to the smooth connection of the sheets in front of the stem, the formation of water vortices is reduced. In order to increase the strength of cast stems in shipbuilding, longitudinal and transverse ribs are used.stiffness.
- Sheet, or welded. These stems are intended for large, fully welded ships with a bulbous bow. In order to prevent deformations in the sheet stems, horizontal spacer sheets are used, which are known in shipbuilding as bow brace. With their help, the connecting joints between the stems and the sheets of the outer skin of the vessel overlap. A ship equipped with ice reinforcements has a longitudinal stiffening rib for the sheet stem.
Conclusion
Today, in the field of shipbuilding, the bulb-like type of stem is more often used. The manufacturing technology of such vessels is more labor-intensive, which entails large financial expenditures. But the experience and the results of the towing tests have shown that these ships have a high speed and are safer.
