What is difference between Stiff ship and Tender ship?

The difference between Stiff ship and Tender ship is Explained in detail in this Post for your reference,

The terms “stiff” and “tender” are used to describe a ship’s response to waves and sea conditions. A stiff ship is one that has a relatively small rolling motion in response to waves and sea conditions, while a tender ship is one that has a larger rolling motion.

The main differences between a stiff ship and a tender ship are:

1. Stability: A stiff ship typically has a higher metacentric height (GM), which means it has more stability and is less prone to rolling. A tender ship, on the other hand, has a lower GM and is therefore more prone to rolling.
2. Hull shape: A stiff ship typically has a fuller hull shape with a wider beam, which provides more stability and reduces rolling. A tender ship, on the other hand, has a narrower beam and a more slender hull shape, which makes it more prone to rolling.
3. Weight distribution: The distribution of weight on a ship can affect its stiffness or tenderness. A ship with a lower center of gravity and more weight in the lower parts of the hull will tend to be stiffer. A ship with a higher center of gravity and more weight in the upper parts of the hull will tend to be more tender.
4. Cargo loading: The way a ship is loaded with cargo can also affect its stiffness or tenderness. A ship with a lower center of gravity due to a well-distributed cargo load will tend to be stiffer. A ship with a higher center of gravity due to an unevenly distributed cargo load will tend to be more tender.

In general, a stiff ship is preferred for its stability and ability to handle rough seas, while a tender ship is preferred for its maneuverability and ability to maintain speed in calm seas. However, both types of ships have their advantages and disadvantages depending on the specific requirements of a given operation or voyage.

Difference between Stiff ship and Tender ship Explained

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.

A very large GM should be avoided for the following reasons:

• The ship will return to the upright very quickly whereby the motion will be jerky causing excessive strain on cargo lashings and possible cargo shift.
• Loose gear will be thrown about.
• It is uncomfortable for crew and injury may result from the ship’s quick motion.
• Structural damage to the ship may occur due to racking.

TENDER SHIP

A tender ship is one with a very small GM caused by KG being too large. This occurs if too much weight is placed high up within the ship. The ship will have insufficient stability, righting moments will be very small when heeled causing the ship to be sluggish and slow to return to the upright. Roll period will be long. (A tender ship is still a stable ship i.e. M is above G.)

A very small GM should be avoided for the following reasons:

• Because of the small righting moments the ship will only offer limited resistance to being rolled, causing the ship to be rolled to larger angles of heel. This will increase the risk of water being shipped on deck.
• The ship will be slow to return to the upright and will tend to remain at the extent of the roll for a comparatively long time. This will create greater and more prolonged strain on cargo lashings and increase the risk of cargo shift.
• Rolling to excessive angles of heel is also uncomfortable for the crew and injury may result.

As a guide, a GM of between 4-8% of the ships breadth is desirable. Container ships that have containers stowed on deck may probably be more suited to a GM value on the tender side of these limits to minimize the stresses on deck container lashings.

Typical curves of statical stability for both a stiff and tender ship are shown.