MOTOR-BOAT NAVIGATION

(PART 2)

PILOTING

PRELIMINARY REMARKS

1. Among the professional navigators the art of navigation is divided into three branches known, respectively, as piloting, dead reckoning, and nautical astronomy. In deep-sea navigation, the methods of dead reckoning and nautical astronomy are usually carried on together, and independently, in order that one set of calculations may serve as a check on the other and thus lessen the chance or possibility of serious errors. They are essentially practiced when out of sight of land and beyond the range of known objects.

2. Piloting refers to methods of fixing a vessel's position when in sight of land, buoys, lightships, and other aids to navigation. It is the art of conducting a vessel in channels and harbors and along the coasts where landmarks and aids to navigation are available and where the depth of water and dangers to navigation are such as to require constant watch to be kept on the vessel's course. Coast piloting involves the same principles and requires the fixing of the vessel's position continuously as landmarks, lights, beacons, and conspicuous points along the shore are passed. It also includes plottingcourses from one point to another and of keeping a continuous record of the time and distance run on each course in order that the vessel's position may, at any required moment, be shown on the chart.

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3. On any cruise, it should be a fixed rule not to be in doubt of the vessel's position at any time even when entering ports considered safe and easy of access or when traversing waters familiar to the navigator. Whenever an opportunity presents itself to check, by bearings of landmarks, the position deducted from the course and distance run, it should invariably be availed of.

To this end the navigator should be provided with the best and most recent charts of the locality over which the cruise is to be made in addition to Sailing Directions containing descriptions of aids to navigation, corrected up to the time of sailing. The compass, lead, and patent log should be in perfect working order. The deviation of the compass, in particular, should be known for each heading, and properly applied, and no articles of a magnetic character be permitted to remain near the compass to create new errors.

In the following, concise explanations will be given of all methods of practical value by which to navigate a power craft and fix its position. During a cruise strict attention and a close study should be given these methods in order that when put into practice, the navigator may use them with despatch and confidence.

Before leaving a dock

4. Clearing a Dock or Mooring. or mooring care should be taken that everything is ready. The engine should be given a few trial revolutions while the boat is still at the dock, to make sure it will start promptly when the moorings are cast off. If the dock is crowded with boats, a general survey should be made of the best way to get clear without unnecessary bumping into other craft. Fenders should be gotten ready in case it becomes necessary to pass close to other boats. If the boat is not equipped with stationary fenders along the gunwhale, a man with a hand cork fender should stand ready to place it at the proper point of contact between the boats or dock as the case may be.

5. When clearing a dock or landing, it is well not to sheer off the bow too sharply by laying the helm hard over, as at a,

d

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Fig. 1, because in so doing, if not sufficiently clear from the dock, the stern of the boat is liable to fetch up heavily against the dock or float, as shown at b. It is better to shove off the bow and then start the engine with the helm amidship, as at c, when with enough headway the dock or float is readily cleared without trouble. The same methods should also be used when starting from a buoy. If the helm is laid over too soon, the stern is very apt to swing over the buoy and foul the propeller. Due regard should also be given conditions of wind and currents when casting off moorings. Both forces have an important bearing on properly leaving and making a dock or landing. The effect on the rudder and propeller in turning maneuvers are different in nearly every boat built and they should be carefully noted in each individual case.

6. Shaping Courses.-After having cleared the harbor for a trip that includes the run across an open stretch of water, where landmarks and aids to navigation are few and far apart or entirely absent, some definite point of departure should be selected from which to shape the course or courses to be run. The shaping of such courses should be done preferably before starting from the dock, landing, or anchorage by consulting charts and Sailing Directions covering the waters over which the run is to be made.

FIG. 1

To shape the course proceed as follows: When the chart is properly spread out, place a parallel ruler between the point selected as starting from, and the first point to be made; move the ruler to the nearest compass rose on the chart until the edge of the ruler rests on the dot in the center of the The intersection of the ruler with the rim of the compass

rose.

rose will give the bearing between the two points, or, which is the same thing, the course to be run. If the compass rose on the chart cannot be reached by one step, or move, take as many steps as may be required, provided the parallelism of the first with the last step is preserved. Proceed in a similar manner to find the second, third, and fourth course, etc. Then find the distance to be run on each separate course by using the dividers, selecting a suitable unit from the scale of miles and stepping it off along the course line.

Generally, when courses are laid out, or plotted, on the chart a pencil line is used to connect the points, but it should be very lightly drawn in order that the chart will not be defaced when the line is erased; nor should the dividers prick holes or otherwise mutilate the chart.

7. Illustrative Example.-To illustrate the foregoing assume that a power boat starts from the government pier at Lewes, Delaware, for a cruise in the bay. It is decided to run across the bay to the buoy marking the upper end of the North Shoal and thence through Ricord's Channel, to the southernmost buoy of the Brandywine Shoal. For a point of departure from which to shape the first course run, the light at the eastern terminal of the Delaware breakwater is selected. Placing the parallel ruler between this point A, Fig. 2, and the first buoy B and then moving the ruler to the compass rose the bearing from A to B is found to be N 41° E, magnetic. It is then found that in order to make the run through Ricord's Channel a straight course may be taken from the buoy B to buoy C. The bearing of the latter from the former is N 40° W, according to the compass rose. Again placing the ruler between buoy C and D at the lower end of the Brandywine Shoal and moving it over the compass rose, as before, the bearing is shown to be N 62° W.

Next, the distance to be run on each course, is found by using the scale of nautical miles at the lower end of the chart. The distance on the first course from A to B is 94 miles, the second course from B to C is slightly over 2 miles; while the distance from C to D is 4 miles, making a total run of close to 16

nautical miles. Assuming that no currents, tides, or wind affects the run and that the boat is capable of maintaining a speed of 10 knots, it will require just 1 hour and 36 minutes to complete the run from A to D.

It will be noticed that the courses given are magnetic, being taken directly from the compass rose which indicates magnetic directions. If the compass on the boat has any deviation,