"EDT Hercules" leaves the shipyard

"La Naval" from Sestao (Spain) last ship 

Time elapses very quickly, more than we usually realize. Yesterday we saw the departure of "La Naval" shipyard's last ship, built there and named "EDT Hercules", and she is the last because there is no one behind to build ... until they get new contracts. This situation is similar to that which occurred about 8 years ago, when this historic shipyard, "La Naval", changed ownership from public Izar to private Construcciones Naval del Norte (CNN).

By that date, October 2006, the LNG gas carrier "Bilbao Knutsen" was launched,  and I put in my other blog a brief post on the launching, with a beautiful night photograph taken by my daughter Natalia. She was the last Izar ship but it was not the last "La Naval" ship, that continued building many ships, some very important.

Ship’s motions at sea

A vessel under sea has two types of movements:

• Desired, to move the ship from one point to another and get she achieves the objectives for which  was built
•  Unwanted, occurring mainly as a result of the waves and wind on the ship and causing trouble, inconvenience and danger to the vessel, persons and cargo, so they try to minimize them.

In this post I will only refer to the second type of movements, motions, relating to ships sailing on the surface.

The ship motion in a 3D space is made up, like any other solid, of the motion of its center of gravity and the movement or rotation around that point. The six possible motions, summarised in the following table, consist of three translations and three rotations, which refer respectively to the trajectory of the center of gravity and the rotations  around the main axes through it. Names are given in Spanish and English languages​​.

Reference axis	Translations	Turns r/ ref. axis
Longitudinal x	surge (avance)	roll (balance ó rolido)
Transversal y	sway (deriva)	pitch (cabeceo)
Vertical z	heave (arfada)	yaw (guiñada)

In the following drawing the three axes are shown, for which the movements of translation and rotation relate.