HINTS ON TACTICAL MANEUVERS
By Lieutenant Commander Jules James, U. S. Navy
1. On making a careful analysis of maneuvers it is realized that the big problem, pervading the entire system, is that of losing bearing with reference to a guide unit. With this well in hand a maximum of time and attention can be given to other details.
2. Most of the following notes and tables were prepared to furnish a systematic solution of this problem so that it could be handled without confusion, and with least effort. They are the result of several years of practical experience with tactical exercises in the fleet, and it is not known where anything to take their place can be found. It is hoped that they will be of use to the service at large.
3. Generally considered, in maneuvers, the prompt attainment of the bearing is more important than the prompt attainment of the distance. Effort to reach both as quickly as possible should be made, but if the bearing is attained promptly it is rather a simple matter to ease in or out to the proper distance. Also, the amount of distance usually lost seldom interferes with a maneuver that is to follow immediately.
Tables
4. Tables "A" (Figure 1) were constructed from data obtained by taking actual observations of degrees (in hearing of the guide) lost in making turns of various amounts. From the observations taken a complete set of curves was constructed, and the tables were taken from these curves. Either the curves or the tables can be used, but the latter were found to be more convenient for use on the bridge.
Table A
Tables of Degrees of Bearing
Lost in Turning
| ? | Distance from guide | Degrees turn | |||||||
? ? 12 knots | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | |
1700 | 3 | 5 | 7 | 9 | 12 | 15 | 17 | 21 | |
3400 | 1 ½ | 2 ½ | 3 ½ | 4 ½ | 6 | 7 ½ | 8 ½ | 10 ½ | |
4000 | 1 | 2 | 3 | 4 | 5 | 6 ½ | 7 ½ | 9 | |
5000 | 1 | 2 | 2 | 3 | 4 | 5 | 6 | 7 | |
6000 | ½ | 1 ½ | 2 | 2 ½ | 3 ½ | 4 ½ | 5 | 6 | |
15 knots | 1700 | 7 | 10 | 13 | 17 | 20 | 24 | 27 | 30 |
3400 | 3 ½ | 5 | 6 ½ | 8 ½ | 10 | 12 | 13 | 15 | |
4000 | 3 | 4 ½ | 6 | 8 | 8 ½ | 10 | 11 | 13 | |
5000 | 2 | 3 | 4 | 6 | 7 | 8 | 9 | 10 | |
6000 | 1 ½ | 2 ½ | 3 | 5 | 6 | 7 | 7 | 8 | |
5. In studying and executing these turns, the surprising thing that is brought to light is the large loss in bearing resulting from a turn at high speed, as compared with the loss resulting from the same turn at a low speed. Only by using data such as is furnished here can bearings be obtained with certainty under various conditions of speed, and of distance from the guide.
6. In turning a ship on the quarter of the guide of course loses fewer degrees in bearing during the turn, and in settling down, than does one on the beam. She loses the same number of yards astern of the point at which she begins the turn, but it was found easier to work with degrees of bearing lost than with yards lost. Consequently, degrees were embodied in the tables. They represent the losses for average position, or bearing, relative to the guide. They will be found sufficiently accurate and extremely useful.
7. To explain the use of these tables:
(See Figure 2.) Suppose that from a position 1,700 yards 30° on the starboard bow of the guide you are to steam out at 60° from the base course, speed 15 knots, to take position at the same distance 60° on the starboard bow of the guide. (If convenient see second figure on page 35 of the publication familiarly known as standing order No. 2.)
8. In actual practice the procedure is as follows:
The 15-knot table shows that at a distance of 1,700 yards from the pivot, you will lose 20° in making a 60° turn. Therefore, you are to resume the base course when 20° ahead of the bearing on which you are to form.
Suppose the course of the guide is 10° (psc).
You wish to take position bearing 70° (psc) from the guide, which means that the guide is to bear from you 250° (psc).
When you start from your initial position the guide bears 220°. As you steam out towards your new position, this bearing gradually increases. When it reaches 230° execute the turn to resume base course. You will lose 20° in the turn and end up with the guide bearing 250° (psc).
If you are taking position 3,400 yards distant, and using the same speed, the table shows that for the same turn you will lose 10°; 4,000 yards distant, 8 ½, etc.
9. The results obtained from the use of these tables have been most satisfactory. Reference to them eliminates the usually disastrous guesswork, and results in a great saving of time, coal, and effort. They are constructed for the same speeds of guide and maneuvering unit, which is the general case.
10. For different speeds of guide and maneuvering unit additional tables can be constructed, but it is not considered that this is desirable as the same speeds generally are used, and these tables will greatly assist in judging all cases, whether the same or different speeds are used.
Table B
Distance from Track of Guide to Turn | |
Degrees Turn | Distance from guide |
10 | 50 |
15 | 80 |
20 | 100 |
30 | 170 |
40 | 260 |
45 | 315 |
50 | 360 |
60 | 450 |
70 | 550 |
75 | 600 |
80 | 650 |
90 | 740 |
100 | 815 |
110 | 900 |
120 | 950 |
Table C
Table of Sines | |
Angle | Sine |
10 | 1/6 |
15 | ¼ |
20 | 1/3 |
30 | ½ |
45 | 7/10 |
60 | 7/8 |
Table D
Distance Per Min. Steamed | |
Knots | Yards |
1 | 33.3 |
2 | 66.6 |
3 | 100 |
4 | 133 |
5 | 166 |
6 | 200 |
7 | 233 |
8 | 266 |
9 | 300 |
10 | 333 |
11 | 366 |
12 | 400 |
13 | 433 |
14 | 466 |
15 | 500 |
16 | 533 |
17 | 566 |
18 | 600 |
19 | 633 |
20 | 666 |
21 | 700 |
11. Table "B," Figure 3, is very useful for turning astern of the guide. It shows how many yards from the track of the guide to execute the turn, in order that you may follow astern. Its use is as follows:
- Lay off the astern track of the guide (which occupies the center of the mooring board.)
- Lay off a line parallel to this track, and at a distance from it equal to the distance given by Table "B" for the turn you are to make. As you approach this line, plot your positions as given by range finder and compass, and when your plot falls on the line, execute the turn.
12. This will put you in correct position astern of the guide, and the division ahead having turned inside or outside will not mislead you.
13. Table "C" is simply a table of sines; Table "D," a table of yards steamed per minute at different speeds.
14. Their uses are illustrated in the same problem, as follows:
Say you wish to gain 1,000 yards towards the flank. If you change your course 10°, the sine of which is 1/6, steam 6,000 yards, then return to the course.
Table "D," which needs no explanation, aids you in determining how long it takes to steam this distance.
Should you change course 30° instead of 10°, steam twice as many yards as you wish to gain towards the flank. This because the sine of 30°, as shown by the table, is 1/2.
15. It may appear that the range finder is all that is necessary for this problem, but in actual practice it often happens that as soon as you turn out the range finder in use will not bear, in which case the tables are invaluable.
Mooring Board
16. The extremely simple method of the mooring board originated by Rear Admiral Burrage, and described below, is especially recommended for use during maneuvers. All who are interested in the mooring board, or who expect to become so at a future date, might well try it out and save this article for future reference.
17. It is believed that the Navy in general is' not familiar with this method, which can be used with great ease in any mooring board problem. Officers, especially navigators, now using other methods, might well investigate this one and consider using it in the future. It is as follows:
Knowing speed and course of guide and the point you wish to reach:
Place the parallel ruler (or the arm of the Universal Drawing Instrument) through the point you now occupy (obtained by compass bearings, and range finder or stadimeter reading) and the point you want to reach. (These may be any two points on the mooring board.)
Slide the ruler (or arm) to the point ahead of the guide representing his course and speed and draw a line.
Now, the point where this line cuts the circle representing the speed you are going to use indicates the course you are to steer.
18. As the course to be taken depends on the speed to be used, you have a number of combinations of speed and course from which to choose.
19. To illustrate, see Figure 4. Guide at C making 12 knots, steering 60°. Range finder and compass bearing show you to be at A. You wish to reach B, 2,000 yards astern of the guide. (Scale 1"=1,000 yards.)
Your maximum available speed is 16 knots,
Mark the point S, which represents the course and speed of the guide (60° being the course of the guide and 12 knots his speed, speed scale doubled. Circles represent speed. Speed scale is arbitrary and independent of distance scale.)
Place the parallel rulers through A and B (where you are and where you want to go.)
Slide the ruler up to pass through point S, and draw a line.
This line cuts the 16 knot circle at the point E, which, projected radially on the outer degree circle, represents the course you are to take, (92-1/2°), if you want to use 16 knots.
Or you may use course 88° at 15 knots (point F), course 82° at 14 knots (point G), course 75° at 13 knots (point H), etc., all shown by this single line.
20. Thus with only one line drawn on the board, we have a wide field from which to choose our course and speed. In certain tactical situations this is most important.
21. Let us suppose you are at B and wish to reach A (same figure).
The mechanical solution is the same (in fact, for any two points on a line drawn through A and B), but since in this case we are to change course to the left instead of to the right we now pick off our course and speed to the left of point 5" instead of to the right as before.
On the same figure, to the left of point S, we find the following:
Point N indicates course 40° at 12 knots. Point P indicates course 30° at 12.6 knots. Point Q indicates course 18° at 14 knots. Point R indicates course 8° at 16 knots, etc. Choose the one that suits your fancy or the particular conditions existing.
For instance, you may be leading a division at B which has to reach point A, and which is now in line of bearing 150° left, speed 14 knots, course 30°. You can change speed to 12.6 knots , which agrees with the present course, rather than change course in this formation.
Or you may be leading this same division in column, at 14 knots, course 30°, when it may be simpler to change course, without signal, 12° to the left to course 18° rather than to change speed.
22. In some cases it will be found that the line cuts certain speed circles twice, in which cases for a certain speed you will have two courses from which to choose the most suitable.
23. Described below is a modification or reversal of this method, often used in maneuvers:
Suppose you are in command of a division of a fleet on course 60°, and maneuvering at 12 knots. You now occupy a position, F, Figure 5, 1,700 yards 45° on the starboard bow of the guide division. (If convenient see bottom figure on page 38 of Standing Order No. 2, for this problem.)
Suppose further that you are to take a position B, abeam of the guide division, and 1,700 yards distant.
While the guide continues on course 60° at standard speed you are going to turn right, say 60°, to lose a certain amount of bearing, and then left to course 30° to arrive at point B, where you resume the base course.
You are going to use standard speed in changing your position.
Now the thing to be determined is, when to change course left to 30° for your run back toward the guide. (The course you use in the initial run out makes no difference in the problem.)
24. This problem is of frequent occurrence and has been considered difficult to execute. The solution below is extremely simple and accurate, while the "time method" solution has been found to be most unsatisfactory.
25. See Figure 6.
You are at point F, and wish to go to point B.
The speed of the guide division is standard, which is 12 knots, the course of the guide 60°. This gives us the point S (speed scale doubled).
26. The mooring board operator is principally concerned with the fact that, after your initial run out, you are going to run in on course 30° with standard speed (12 knots).
He already has marked on the board:
- Point C, at the center of the board representing the guide.
- Point S representing the course and speed of the guide.
He now marks point B, at which you wish to arrive, and point E, which represents the course and speed you are going to use when, after your initial run out, you turn back to approach point B.
He lays his ruler through points E and S, backs it down to B and draws a line.
Come to the course 30° when you will swing onto this line in so doing.
NOTE: The range finder and compass plots show your approach to this line, and when you plot just above it, it is time to come to the course 30°. It makes no difference what point of the line you strike as any point on this line corresponds to point A in the Burrage method described above, of which the "answer" is point E.
27. Should a later plot show that you missed the line, or having hit it, that you had got off, the mooring board operator gives you a correction by using the method originally described above, i.e.:
Places the ruler through the present plot and point B, slides it to S, draws a line and picks off new speed or new course depending on which it is more convenient to change.
In line of bearing a change of speed probably would be more convenient; in column, a change of course.
(For other cases where this solution is used, see pages 38, 41, 66, 67, 68, etc., of Standing Order No. 2.)
28. It will be noted that in some cases after getting on the line you steam parallel with the guide before turning in. As long as your speed is the same as that of the guide, this makes no difference. Should it be other than that of the guide, allowance must be made for the distance that will be lost while steaming parallel to the guide. This allowance, as well as the allowance for the distance you are due to lose in the turns, is best made by drawing the line to pass ahead of 5 a distance equal to the loss.
29. With this easy and accurate method available, there is small excuse maneuvers of this class occasioning trouble or delay. Its application is easier and infinitely better than guesswork, and the problem requires less than ten seconds of time for the average mooring board operator. The line generally is drawn before the signal for the maneuver is executed by the flagship.