[QUOTE=Topsail;131683]Effectively, there is no link between Gross Tonnage and deceleration. The momentum depends upon the displacement and the square of speed of that vessel. Thus a lighter ship will gain or lose speed faster than a deeply loaded vessel. A large and fully laden tanker will travel longer after the engine is stopped. The reverse will happen when the tanker is in ballast and thus travel at a lesser distance. After given engine movement, a loaded tanker will come to the designed speed slower than the same tanker in ballast.
The shape of the underwater part of the hull (Coefficient Block cb) plays an important role. Two vessels of the same displacement will have entirely different accelerating and decelerating speeds. Through experience, a vessel which has finer lines and cutting edge bow will travel lesser distances after the engine stopped but will reach the designed speed faster. Under keel clearance plays an important role. If it is reduced, the ship will take longer to reach her designed speed from stop as well as she will travel longer when the engines are stopped.
The rate at which a ship gains or losses speed in different circumstances depend chiefly on the momentum, displacement of the ship, coefficient block, loading conditions, draughts & trim, air draft & sail area, engine type & power, size & type of propeller vs. cavitations, bow type vs. bow waves, under keel clearance vs. squat (Bernoulli & Ventury effects) water restriction flows, pressure of the hull lateral wetted area, rudder wetted area vs. breaking forces, air density vs. outside temperature, wind, anti-fouling paint age vs. marine growth.
The corresponding rates of gaining or losing speed will also differ largely from one type to another. When increasing or decreasing speed by changing revolutions, the rate of acceleration or deceleration is affected by so many factors and varies so much in different parts of the total speed range, that it would be difficult to recommend any mathematical method of allowing accurately deceleration figures. A black out stopping distance from 10 knots can easily be in the range of 3 nm. So within 1 nm from a berth, you better be at Dead Slow speed if you don’t want to ruin your day.
Trials in a shipping yard basin along with accelerometers to establish deceleration curves to then be transposed into a mathematical formulas … but only good for that particular vessel & conditions. Finally, I think that it would be easier to find a unified formula for the universe than one for a all vessels deceleration ![/QUOTE]
And Gross Tonnage has absolutely nothing to do with displacement. . . .