Stability Flashcards
What is the definition of the forward and after perpendicular?
An imaginary vertical lined drawn to the waterline at the point where the summer load line cuts.
What is the definition of displacement?
The weight of the vessel in tonnes.
What is the definition of load displacement?
The weight of the vessel when loaded down to the summer load line.
What is the definition of light displacement/ lightship?
The weight of the vessel when empty.
What is the definition of deadweight?
The difference between the lightship and present displacement.
What is the definition of gross tonnage?
The total internal volume in tonnes.
What is the definition of net tonnage?
The total weight of the cargo carrying area, does not include accommodation, engine room, etc.
What is the definition of TPC?
(Tonnes per centimetre)
- The amount of tonnage needed to change the vessels draft.
What is the definition of FWA/DWA?
The amount the vessel can submerge her marks to in fresh and dock water.
What is the definition of Free surface effect (FSE)?
Created by the movement of cargo or liquids in a tank?
What is the definition of GZ?
Is a righting leave which allows us to see how the ships act on a GZ curve?
What is the definition of GM?
The vertical distance between the centre of gravity and metacentric height.
What is the definition of KG?
The vertical distance from the keel to the centre of gravity.
What is the definition of TCG?
(Transverse centre of gravity)
The distance from the centre of gravity to the edge.
What is the definition of KM?
The vertical distance from the keel to the metacentric height/ GM.
What is the definition of MCTC?
Moments to change vessels trim by 1cm.
What is the definition of LCG?
The distance from aft perpendicular to the centre of gravity.
What is the definition of LCB?
The distance from aft perpendicular to the centre of buoyancy.
What is the definition of KB?
The vertical distance from the keel to the centre of buoyancy.
What is the definition of list?
the centre of gravity is moved away from the centre line due to uneven loading.
What is the definition of heel?
An external force is pushing the vessel over.
What is meant when GM is negative?
Vessel is in an unstable condition.
What is meant when GM is positive?
Vessel is in a stable condition.
What is meant when GM is the same?
Vessel is in a neutral condition.
What is meant when both G and B are off the centreline?
Vessel is listing.
What is a hydrometer?
An instrument used to work out the density of the water.
Collect the samples from about halfway down the vessel’s draft, wipe the hydrometer and place them in the water twisting as you do so.
Take care when reading, make sure to read the true reading.
What are load lines?
- Forward and Aft draft marks must be placed on the perpendiculars.
- The load line disc/ plimsoll mark shall be placed at a point midway between the perpendiculars.
What are the specifics and dimension of load lines?
- Forward and Aft draft marks must be placed on the perpendiculars.
- The load line disc/ plimsoll mark shall be placed at a point midway between the perpendiculars.
Dimensions: - All lines are 25mm thick.
- The centre of the disk lines up with the summer load line.
- All lines (TF, T, S, W, etc.) are 230mm long.
- Tropical load line is 1/48 above the summer draught line.
- Winter load line is 1/48 below the summer load line.
- The Winter North Atlantic line is 50mm below the winter load line.
- If the vessel is being loaded in dock water or fresh water, DWA and FWA should be considered in calculations, due to different water densities.
Load lines calculated from the top of marks.
Drafts are read from the bottom of the mark.
