Bluff bow

A bluff bow is part of the hull of a Bateau: it is about one bulge to front, on the level of the brion, below the stem.

The principal function of the bluff bow is to create a Vague in front of the normal system of vaguenesses generated by the ship on the way; at a certain speed, the hollow of this additional wave coincides with the top of the vagueness of stem, which is found cancelled: hydrodynamic resistance is thus reduced and the ship can go more quickly for the same power. Moreover, first Crete of vagueness is moved with the front one, which increases virtually the Length with the floating of the ship and thus its theoretical maximum speed. An improvement of 20% of resistance can be hoped with a bulb, but this one will often need preliminary tests.

However, this system functions only for one speed and a given immersion. It is especially applied to the ships cargo liner which in general know only two types of navigation: with full Light load or S, and at fixed speed. It is also applied to the warships as the frigates which need speed.

A bluff bow implies also great constraints of construction, because it is difficult to conceive it with developable surfaces, easier to build. On small boats, the surface of drift and immersed volume change also considerably with the addition of a bulb; it is seldom applicable to the low-size boats. A bulb is also directly subjected to the shocks of meeting with the waves, in particular in the cases of tossage or Slamming.

The bulbs can also know other utilities, as on the oceanographical ships where they can be used as points of observation, or on the frigates where they shelter a dome Sonar.

Source

External bond

Gallery of bluff bows.

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