indicated by the length of m .... g. Similarly, joi n ing w and m, and considering m the head and w the foot of the vector 

 so formed, 10 .... m represents the travel of unit M in respect to the wind. If this vector is reversed and w made the 

 head, then m . . . . w represents the travel of the wind in respect to unit M or shows the apparent wind on M. 



From the above it will be noted that all lines in the Vector Diagram are vectors, which have in them only the quantities 

 of direction and rate of travel. No other quantities can be directly obtained from this diagram. 



The Relative Plot is the second diagram employed in the Relative Movement Method. This diagram has a fixed point, 

 representing the unit used as a guide, and such Relative Lines as the solution may produce. These Relative Lines show 

 direction and distance travelled, both relative to the Guide Unit. The Relative Plot, therefore, has only the quantities of direction 

 and distance. 



The common factor in both the Vector Diagram and the Relative Plot is direction. Hence, the interchange of data from 

 one diagram to the other must be based upon this common quantity. The element of Time, required in practically all problems 

 is the factor by which speed, from the Vector Diagram, is converted to Distance in the Relative Plot or vice versa. The 

 solution for Time alone may be reached by dividing the distance, from the Relative Plot, by the speed, from the Vector 

 Diagram. The two are interchanged through their common quantity of direction. 



Although the majority of the problems dealt with herein are solved by the Relative Movement Method, recourse is fully 

 had to other methods which more readily yield the desired results. Particular mention must be made of the Navigational 

 Plot, which can always be utilized as a proof of the solution, regardless of what method was actually used in working the 

 problem. A solution by this method may be extremely laborious, involving trial and error, but once the results are obtained by 

 some easier and quicker method, it is a matter of but a few moments to obtain a check by completing the Navigational Plot. 

 In actual practice, whenever time permits, it should be employed not only to check the results, but also to insure that there is 

 no navigational hazard in the direction of your own ship's motion. 



It must be pointed out that the mere working out of a problem on the Maneuvering Board is not enough. The progress 

 of your own vessel along the line of relative movement must be checked by both bearings and rangefinder ranges. In some 

 instances the guide may change both course and speed considerably without previous signal. It is far easier to set up another 

 problem based on your instantaneous position than to try to involve the previous solution with the problem presented by the 

 new conditions. All officers should be familiar with the simplest types of problems and their rapid solution. The operator at 

 sea, however, should never become so intent on figuring out his next proper move on a Maneuvering Board that he fails to 

 keep a sharp lookout for incidental ships, such as other maneuvering units, merchant ships, or aircraft carriers, about to launch 

 or land aircraft, which may happen to wander into his set-up. Also, no shoals or menaces to navigation are shown on the 

 Maneuvering Board. A lack of alertness in this regard will never be compensated by the ability to find perfect solutions on 

 a Maneuvering Board. 



SUGGESTIONS 



The Maneuvering Board, HO 2665, is especially designed to facilitate the solution of problems by Vector Diagrams and 

 Relative Movement Plots, although any chart equipped with a compass rose may be used if dividers, parallel rulers, and a 

 proper scale are available. 



When using the Maneuvering Board, place the Vector origin, e, at the center of the diagram. 



Letter the head and foot of each vector as it is drawn and indicate the head by an arrowhead. Leave the foot plain or 

 enclosed in a small circle. Use small letters in the Vector Diagram to correspond with capital letters designating the same 

 unit in the Relative Plot. Any letters desired by the operator may be used to indicate the various units concerned. In this 

 publication, 67 is used to designate the Guide unit and g indicates the head of the Guide's vector. If a single maneuvering 

 unit is involved, it is usually designated M, with the corresponding m as its vector head, but this lettering may be varied for 

 the sake of clarity. 



In the Vector Diagram, it is suggested that the letters e, g, and w be used as herein. In the Relative Plot, indicating the 

 unit Guide by 67 will tend to prevent errors. 



In the figures illustrating the various examples in this publication, distinctive lines are used to emphasize the construction 

 of the set-up. For ordinary solution of problems, this is not necessary. 



Courses and bearings should be drawn in their true directions. Relative bearings are easily found by orienting the dia- 

 gram. The application of variation and deviation to true courses and bearings after the solution is reached readily yields the 

 magnetic or compass courses and bearings, with less chance for error than if the conversion were attempted earlier in the 

 solution. 



No set rule can be given for the scale to be used in the Relative Plot. It should be as large as the size of the board will 

 permit. 67 may be placed at any point, but usually it is more convenient to place it at the center of the board, superimposed 

 upon e. Care should be taken that the Relative Plot and the Vector Diagram are not confused thereby. Sometimes, by plac- 

 ing 6? elsewhere, a much larger scale can be employed, with consequent increase in accuracy. 



Care should be exercised to differentiate between the scale used in the Vector Diagram and the scale used in the Relative 

 Plot. These diagrams are entirely separate. The habit of noting in the upper right-hand corner of the board the proper scales 

 used, such as 1 division = 2 miles, or 1 division =3 knots, will generally prevent confusion in this matter. Also, when using 

 HO 2665, if the scales on the side are employed, a D over the distance scale used and an S over the speed scale employed, will 

 further tend to reduce error. Confusing the distance scale and the speed scale is the most frequent source of mistake made 

 by the beginner. Finally, the scales chosen should be as large as practicable. 



Strive for accuracy but not by the expenditure of excessive time. It is much more advantageous for the officer conning 

 to have an approximate course and speed to start with, modified as necessary later for the exact course and speed required, 

 than to be slow in changing station. The standard of accuracy required should be sufficiently exact as to produce results which 



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