Question

What is The Effect of wind and waves

When a ship is inclined by an external force, such as wind and wave action, the centre of buoyancy moves out to the low side, parallel to the shift of the centre of gravity of the immersed and emerged wedges, to the new centre of gravity of the underwater volume. The force of buoyancy is considered to act vertically upwards through the centre of buoyancy, whilst the weight of the ship is considered to act vertically downwards through the centre of gravity. These two equal and opposite forces produce a moment or couple which may tend to right or capsize the ship. The moment is referred to as the moment of statical stability and may be defined as the moment to return the ship to the initial position when inclined by an external force.

Question

What is The Effect of trim on tank sounding.

A tank sounding pipe is usually situated at the after end of the tank and will therefore only indicate the depth of the liquid at that end of the tank, if a ship is trimmed by the stern, the sounding obtained will indicate a greater depth of liquid than is actually contained in the tank. For this reason it is desirable to find the head of liquid required in the sounding pipe which will indicate that the tank is full.

Trim may be considered as the longitudinal equivalent of list.

Trim is also known as longitudinal stability. It is in effect transverse stability turned through 90°.

Instead of trim being measured in degrees it is measured as the difference between the drafts forward and aft. If difference is zero then the ship is on even keel. If forward draft is greater than aft draft, the vessel is trimming by the bow. If aft draft is greater than the forward draft, the vessel is trimming by the stern.

Question

What is Reserve Buoyancy?

When a floating vessel displace its own weight of water. It is the submerged portion of a floating vessel which provides the buoyancy.

The volume of the enclosed spaces above the water line are not providing buoyancy but are being held in reserve. If extra weights are loaded to increase the displacement, these spaces above the waterline are there to provide the extra buoyancy required.

Thus, reserve buoyancy may be defined as the volume of the enclosed spaces above the waterline. It may be expressed as a volume or as a percentage of the total volume of the vessel.