What is meant by stiff ship?

A stiff ship is one with a very large GM caused by KG being too small. This occurs if too much weight is placed low down within the ship. The ship will be excessively stable, righting moments will be so large as to cause the ship to return to the upright very quickly when heeled. Roll period will be short.

What are stiff and tender ships?

A vessel with little or no metacentric height is said to be tender. Weight added low down in the vessel lowers the vessel’s centre of gravity (G) and consequently causes an increase in the vessel’s metacentric height (GM). A vessel with a large metacentric height is said to be a stiff vessel.

What is the meaning of tender ship?

A ship’s tender, usually referred to as a tender, is a boat, or a larger ship, used to service or support other boats or ships. This is generally done by transporting people or supplies to and from shore or another ship.

What is unstable ship?

When the ship’s metacenter lies below the center of gravity, the moment acts in the opposite direction, increasing the angle of heel. Hence , the vessel will not return to the upright position.Then the vessel is said to be unstable ie, GM is negative.

What is GM of ship?

The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre.

What are the three types of ship stability?

There are three types of equilibrium conditions that can occur, for a floating ship, depending on the relation between the positions of the centre of gravity and centre of buoyancy….Intact Stability of Surface Ships:

• Stable Equilibrium: Study the figure below.
• Neutral Equilibrium:
• Unstable Equilibrium:

How do you calculate GM of a ship?

GM – Metacentric Height: This measurement is calculated by subtracting KG from KM (GM = KM – KG). GM is a measure of the ship’s initial stability.

What do you call a small boat?

dinghy, dory, rowboat – a small boat of shallow draft with cross thwarts for seats and rowlocks for oars with which it is propelled. gig – long and light rowing boat; especially for racing.

What causes negative GM?

A negative initial GM may occur due to the following reasons: Free surface effects. Flooded compartments. Top heaviness – or excessive loading on upper decks.

What is trim and list of ship?

Listing vs Rolling vs Trimming “Listing” is a nautical term to describe when a vessel takes on water and tilts to one side. A ship can list either to port (left) or starboard (right). By contrast, a ship is said to be “trimming” when she tips forward or backward.

What is rolling period of ship?

Roll period is how quickly a vessel return to upright position while rolling. So it is the time a ship takes from upright position to going to a particular angle on port side and then going to a angle on starboard side and then again returning back to upright position (zero list position) during natural rolling.

What is a dory boat?

dory, small boat with pointed ends and high, flaring sides. A dory may be up to 22 feet (7 m) long and commonly has a narrow, V-shaped stern and a narrow, flat bottom. It is a seaworthy boat that can be rowed, engine-driven, or sailed; it is used extensively by New England fishermen. dory.

What causes a ship to be stiff?

A stiff ship is one with a very large GM caused by KG being too small. This occurs if too much weight is placed low down within the ship. The ship will be excessively stable, righting moments will be so large as to cause the ship to return to the upright very quickly when heeled.

What is the opposite of a stiff ship called?

The opposite of a stiff ship is called a tender ship, which has a very small metacentric height and, as a result, a very small righting moment. A tender ship has a very long roll period, which means that the vessel will return to upright very slowly and has insufficient stability.

What is the difference between stiff ship and tender ship?

When this height is Greater ship called Stiff ship and when it is small ship is called the Tender ship. In both cases, they have a different effect. The stiff ship has her Centre of Gravity (COG) close to its keel (bottom). This occurs if too much weight is placed low down within the ship. In other words, she has a large ‘metacentric height (GM)’.

What is the effect of a stiff ship on rolling moment?

A stiff ship will tend to respond to the wave profile more rapidly, tending to assume the slope of the passing wave. So, even though a stiff ship will develop rolling moment easily in a passing wave, it will also require less force to return to an upright position, rendering the ship more stable. Also, the time period of the rolls would be shorter.