Navigational calculator
United States Patent 1191 1111 3,876,866 Kaspar 5] Apr. 8, 1975 NAVIGATIONAL CALCULATOR 3.193.195 7/1965 Jeffries 235/88NX Inventor: Peter Dalzell p Dover, Del. 3,497,678 2/1970 Warner 235/78 N X FOREIGN PATENTS OR APPLICATIONS [22] Sept 1974 916.168 1/1963 United Kingdom 235/61 NV [21] Appl. No.: 505,164  
 Primary E.\&#39;aminer-Lawrence R. Franklin [52] US. Cl. 235/88 51 Int. Cl G066 3/00 [571 ABSTRACT [58] Field 61 Search 235/61 NV, 78 N, 88 N A navigational Calculator for solving vector problems has three concentrically mounted rotatable members [56] Ref r n Cit d having cooperating speed scales, an outer 360 com- UNITED STATES PATENTS pass rose, an inner 360 compass rose and a boat 2.9l6,207 12/1959 Vohland 235/61 NV 2,996,242 8/1961 Bannister 235/88 N X 5 Claims, 6 Drawing Figures O o x O O &#39;2 on? F-ZYENTEEAPR 8 i975 SHEETIUEZ FIG.2  
 FIG.3  
 NAVIGATIONAL CALCULATOR BACKGROUND oF THE INVENTION 1. Field of the Invention This invention relates to a simplified navigational calculator for determining direction and speed of the actual wind when the direction and speed of both the boat and the apparent wind are known. It is also useful for solving other problems encountered in navigating boats. I  
  2. Description of the Prior Art &#34;I n boating and sail racing it is important to know the direction and velocity of the actual or true wind to determine the apparent wind for any given boat heading and-many devices have been proposed for obtaining such information. US. Pat. No. 3,625,417 to Slauter describes one such device which comprises as many as seven parts and a somewhat involved method for using it. The American Practical Navigator (Bowditch 1966) discloses additional methods.  
 . SUMMARY OF THE INVENTION I have now invented a navigational calculator which is simplified in construction and requires but a relatively few steps to operate. For example, when it is desired to find the speed and direction of the true wind and the direction and&#39;velocity of both the boat and the apparentwind are known, only three steps are needed with this calculator. Other boating problems may also be solved with a minimum of steps.  
 1 DESCRIPTION OF THE DRAWINGS FIG. 5 is a top view of the assembled calculator showing step two in the solution of the problem.  
  FIG. 6 is a top view of the assembled calculator showing step three in the solution of the problem.  
  Referring now to the drawings and particularly to FIG. 1 there is shown in exploded view an embodiment of the invention showing the three structural components 10, 11 and 12.  
  The first structural component is the circular base member which has a series of concentric circles running from the center out to the periphery. Italso has a first series of parallel lines 21 and a second series of parallel lines 22 which are perpendicular to the lines 21. These lines serve to form rectilinear grid lines or squares over the entire face of the member 10. For purposes of simplicity in the drawing, only one quadrant of base member 10 shows the complete circles and squares but it is understood that in practice the other quadrants are similarly complete.  
  The distance between any two consecutive circles equals the distance between any two consecutive parallel lines. The distance between two consecutive circles represents a unit of speed and the distance between two consecutive parallel lines also represents a unit of speed. The unit of speed can be any assigned number either equal to, greater than, or less than unity so that higher or lesser speeds can be handled by the calculator. It is advantageous to make these circles and lines of contrasting colors for ease inreading. It is also advantageous in disc 10 to have two perpendicular grid lines or diameters 23 and 24 passing through the center point of the disc to be accented overthe other gridlines and the concentric circles. These diameters, which are the central lines of the aforementioned parallel lines 21 and 22, can be considered as dividing the base disc 10 into four equal segments.  
  The second structural component, intermediate disc 11, is made of transparent material with .a 360 compass rose&#39;circumferentially disposed thereon. In one embodiment the intermediate disc is made of a transparent circular sheet 25 with an opaque compass ring 26 attached thereto, as by glueing. Thefdegrees of the compass ring 26 are disposed so the degree linesextend to the inner edge 27 of the ring 26. The compass ring 26 is used to show the direction of the true wind. The relationship of transparent sheet 25 and ring 26 is more clearly shown in FIG&#39;. 2. I I  
  The third structural component, inner ring 12, comprises a 360 compass rose 30 with the degree marks extending to the outer edge 31 of the compass rose. The ring 12 has an integral diameter in the shape of a transparent boat pointer 32, the bow of the boat pointing to the 0 mark and the stern point to the l mark of the compass rose. The boat point also has an integral diameter 33. It is to be noted that since the boat pointer 32 and compass rose 30 are integral witheach other, they rotate as a unit. Ring 12 is smaller in diameter than compass ring 26 of disc 11 so that in the assembled c&#39;alculator compass rose 30 rotates within compass ring 26, as shown in FIGS. 3 and 4, in abutting relationship. The compass rose 30 is used to show the direction of the apparent wind.  
  Each of the three components 10, 11 and 12 has a central opening through whhich a pin, bolt or other fastening device is inserted to hold the three components in aligned and rotatable relationship. Each of the three components is independently rotatable. It is to be understood that any suitable material such as metal, wood, plastic, etc. can be used for making the various parts. It is essential that sheet 25 be made of transparent material so the face of disc 10 is completely visible at all times. The boat diameter can be a very. narrow strip in the shape of an arrow or, as previously indicated, in the shape of a boat. The transparent parts of the calculator are made of glass or relatively rigid clear plastic such as Lucite, Mylar, etc. which can be written upon with pencil, ink, crayon or the like. Lucite and Mylar are trademarks of the Du Pont Co.  
  FIG. 3 is a sectional view illustrating the manner. in which the calculator is assembled and held together by a fastening device 34.  
  FIG. 4 is a top view of the assembled calculator showing a first step in the solution of a boating problem.  
  The operation of the calculator will now be described with particular reference to FIGS. 4, 5, and 6. When a boat is heading 270 at a speed of 10 knots and the apparent or relative wind is 045 at a speed of 20 knots, it is desired to determine the direction and velocity of the actual or true wind. The answer is obtained as follows.  
  l. Rotate the inner ring 12 so the boat pointer 32 and its diameter 33 point to the boats heading of 270 on the outer ring 26 as shown in FIG. 4.  
 2. Without disturbing rings 26 or 30, rotate the bot-.  
 tom or base disc until one of the two accented diameters 23 (or 24) points to the apparent wind direction of 045 on the compass ring 30 of inner ring 12, as shown in FIG. 5. Starting from the center point of the calculator and moving toward the stern of the boat pointer 32, count the number of circles corresponding to the boats speed. Assuming each circle represents 1 knot, count to thetenth circle since the boats speed has been given as 10 knots. From that point, and moving along an intersecting line which is parallel to the heavy diameter :23 which points to 045, count 200 squares in the direction of 045 to represent the 20 knot speed, of the apparent wind. At the twentieth squarernalteafrnark on the transparent sheet 25 with dition of the calculator at this stage is shown in FIG. 5.  
 &#39; 3. Rotatethj bottom or base disc 10 once more so the heavy diameterfline passes through the aforesaid mark. This diameter now points to the direction of the true wind on the outer ring 26, in this case 343 as shown in FIG. 6. The velocity of the true wind is obtained bysimply counting the number of circles between ,the aforesaid mark and the center of the calculator. In this&#39;casejthe number of circles is seen to be and accordingly the velocity of the true wind is 15 knots. v  
  is thus apparent that in three moves and the making of buto n&#39;e inarkon the calculator the answer to the problemnis obtained in a very rapid manner.  
  Otherhavi&#39;gational problems can also be solved with the calculato&#39;r For example, when the speed and direction of both the boatand the true wind are known, it is possible to ascertain the direction and speed of the apparent wind. This is useful information in determining what sail should be hoisted when the boat rounds the mark. It is assumed the true wind has a direction of 343, has a speed of 15 knots, the new boat heading upon rounding the mark wilkl be 30 and the boat speed will be 7 knots per hour. The solution is obtained as follows. I i  
  l. Rotate the circular base member 10 so one of the accented diameters 23 or 24 points to 343 on the outer ring 26. Starting from the center point of the calculator and going toward the 343 mark, place a pencil mark on that diameter at the point where it intersects the 15 knot speed circle. This mark can be referred to as the true wind mark.  
  2. Next, without disturbing the base member 10 or the intermediate disc 11, rotate the boat diameter 33 and the boat pointer 32 until the front of the pointer points to 30 on the outer ring 26. Starting from the center point of the calculator and moving toward the back end of the p pointer, put a pencil mark on the transparent boatpointer 32 at the point where the boat diameter 33 intersects the 7 knot speed circle. This sec- 0nd mark can be referred to as the boat mark.  
  3. Rotate only the circular base member 10 once more so one of the aforementioned parallel lines runs through, or as close as possible to, each of the said two pencil marks. One of the accented diameters 23 or 24 will now be parallel to the line running through the two marks and that diameter, sighting in the direction of the first mark, will be pointing to the apparent wind direction on the compass rose on the inner ring 30. In this case that direction will be seen to be 328. The number of speed marks between the two pencil marks will be the speed of the apparent wind, in this case, about 20 knots.  
  It should be noted that while the outer ring 26 has been referred to as the true ring, it can be used to designate magnetic headings instead. If so used, the wind direction will be a magnetic heading rather than a true direction.  
 I claim:  
  1. A navigational calculator for use in boating comprising a circular base member having a series of concentric circles and rectilinear grid lines the distance between any two consecutive circles equalling the distance between any two consecutive parallel lines of the grid;  
 an intermediate transparent disc member with a 360 compass rose circumferentially located thereon; and  
 an upper, inner ring member carrying a 360 compass rose on its circumference and having an integral diametral member running from the 0 mark, through the center of the circle defined by the ring, to the 180 mark of the compass rose; each of the aforesaid members being mounted on a common central axis and rotatable with respect to each other, the said inner ring member having a diameter smaller than that of the intermediate disc member so their respective compass roses rotate in abutting relationship.  
  2. A calculator according to claim 1 wherein the diametral member of the said inner ring member is transparent.  
  3. A calculator according to claim 2 wherein the transparent diametral member is in the shape of a boat, the bow pointing to the zero degree mark and the stern pointing to the 180 mark.  
  4. A calculator according to claim 1 wherein the circumferential area of the intermediate disc carrying the compass rose is opaque.  
  5. A calculator according to claim 1 wherein the two perpendicular grid lines passing through the center of the circular base member are accented over the other gird lines.