SPEED OF APPROACH
The major difference between the neophyte and the experienced ship handler is the speed at which they work. The less experienced ship handler generally works too fast. Don't equate increased speed with increased ability.
When beginning an approach to a berth, speed should be reduced to bare steerageway. This is much slower than most people realize and it is a rare ship that under calm conditions, will not steer at speeds of less than 2 knots if given a chance to respond to her rudder. By using the engine in short bursts or kicks with hard over rudder, even the worst handling ships will respond. If additional response is needed, use the tug or work against an anchor rather than increasing headway. If unsure of speed take all headway off the ship you are now certain of her speed through the water and then come ahead as required to steer and make minimum headway to the berth.
There are several methods available by which the you can judge
speed:
1. Doppler log giving direct readout.
2. Fixes by radar or visual bearings.
3. Position of the ship's quickwater.
4. Observation of passing objects and comparisons with known distances.
The Doppler log gives direct readout of speed over the bottom (or speed through the water when the ship is offshore and the log is indicating speed referenced to water mass). Fixes by radar or visual bearings are neither convenient nor sufficiently accurate for determining speed in a docking situation.
The position of the ship's quick water, which means the wash from her propeller as the engine goes astern, is useful to the shiphandler at low speeds. If that quickwater falls behind the ship when the engine is put astern, the vessel's speed is 3 knots or more. When the quickwater begins to move with the ship, the speed is about 2 knots. When the wash reaches the midsection the ship is dead in the water. Since 2 knots is a comfortable approach speed for an average size ship, it's convenient to be able to put a light on the water at night and then go astern until you see by the position ofthe ship's quickwater that the speed has been reduced to the desired 2-knot speed.
Some experience is needed before the relative motion of passing objects can be used to estimate ship's speed, although it is possible for an experienced seaman to judge speed visually with surprising accuracy. How does an experienced seaman become experienced? By practice! Estimate your ship's speed of approach at every opportunity and compare it with the speed shown on a Doppler log, or the speed indicated by the time required to advance along a pier of known length, or by comparing your estimate with that of a more experienced ship handler such as the docking master. When estimating ship's speed look at objects abeam or a little abaft the beam since an optical illusion occurs when looking ahead. Objects forward of the beam do not seem to be moving and if you use them as a reference you'll find your ship is going too fast when she reaches the berth. Stand in the wheelhouse at night when the ship's speed is most difficult to judge and, while watching an object ashore located forward of the beam, slow your ship to a minimal speed. Now look abaft the beam and see how fast you are actually moving.
Judging speed visually can be hard, but it is possible to develop some rules of thumb to improve your accuracy. The shiphandler must differentiate between speed over the ground and speed through the water. Obviously the speed over the ground determines the speed at which the ship arrives at the pier, while speed through the water affects the ship's response to her rudder. Docking while stemming the current is an advantage since the ship handler can steer even when moving at minimal speeds relative to the berth; docking with the current from astern creates the opposite situation and requires a greater degree of skill.
