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15 Cards in this Set
- Front
- Back
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Block Coefficient |
the ratio of the volume of displacement of the hull at a particular draft to that of a rectangular block having the same extreme depths of length, breadth and draft |
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Formula for displacement |
L x B x D x p x Cb |
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TPC |
How many tonnes it takes to sink/ rise the ship by 1cm. Helps us to determine how much cargo we can load. Given for a range of drafts in the stability book. |
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Formula for DWA |
DWA = FWA x ( 1025- P Dock Water) / 25 |
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Steps to find out how much cargo remains to be loaded |
Step 1: Calculate present mean draft Step 2: Calculate sailing draft (summer draft + DWA) Step 3: Calculate sinkage allowed (sailing draft - present draft) Step 4: Calculate cargo to load (first convert TPC , then multiply the sankage by the new TPC value) |
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Stability |
the ability of a vessel to return to the upright position after it has been inclined or heeled by an external force. |
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The Centre of Gravity |
the point at which all the vertically downward forces of weight of the vessel can be considered to act. Its psn can be defined as some distance above the keel, some distance port or stbd of or on the c/l and some distance fwd or aft of the mid- length. |
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The Centre of Buoyancy |
the point at which every upward force of buoyancy can be considered to act |
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Formula for the Righting Moment |
Displacement x Righting lever = W x GZ (tonne metres) GZ = GM Sin 0 = W x GM Sin 0 |
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Transverse Metacentre (M) |
Vertical lines drawn from the centre of buoyancy at consecutive angles of heel will intersect at a point called the metacentre |
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What is the name of: GM, KM and KG |
KM - Height of metacentre GM - Metacentric height KG - Height of centre of gravity |
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Stable equilibrium |
G is below M, the lever is positive and the couple will return the vsl to its upright psn |
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Neutral equilibrium |
G coincides with M, there is no couple or lever. GM is zero, no tendancy to return to the upright - dangerous condition |
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Unstable equilibrium |
G is above M, lines of force have seperated, GZ has a negative value, tendancy to incline for small angles of inclination- very dangerous condition, easily capsized. Tend to fall over and lie at an angle of loll |
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Calculation of KG |
Step 1: write down all items, their weights and their KG's Step 2: Calculate the moments for all items ( w x d) Step 3: Total the weights and the moments Step 4: Calculate the final KG ( sum of mom. over sum of weights.) |
