NAVIGATIONAL PLANNING AND DISPLAY METHOD FOR THE SAILOR'S DILEMMA WHEN HEADING UPWIND

• US 20090287409A1
• Filed: 04/12/2007
• Published: 11/19/2009
• Est. Priority Date: 04/12/2006
• Status: Active Grant

• Current Assignee: Craig Summers
• Original Assignee: Craig Summers
• Inventors: Summers, Craig
• Granted Patent: US 8,135,504 B2
• Time in Patent Office: Days
• US Class Current: 701/202
• CPC Class Codes: B63B 2035/009 Wind propelled vessels comprising arrangements, installations or devices specially adapted therefor, other than wind propulsion arrangements, installations, or devices, such as sails, running rigging, or the like, and other than sailboards or the like or related equipment
• CPC Class Codes: B63B 49/00 Arrangements of nautical instruments or navigational aids nautical measuring instruments G01C; radio navigation, analogous arrangements using other waves G01S
• CPC Class Codes: B63B 79/40 for controlling the operation of vessels, e.g. monitoring their speed, routing or maintenance schedules
• CPC Class Codes: G01C 21/203 Specially adapted for sailing ships
• CPC Class Codes: G06G 1/0052 for air navigation or sea navigation
• CPC Class Codes: Y02T 70/00 Maritime or waterways transport

Abstract

A method is disclosed that resolves a long-standing seafaring problem of how close to the wind to sail. Sailboats need a convenient way to determine the optimal heading to minimize the Tacking Time to Destination (TTD). Unlike Velocity Made Good (VMG), the method disclosed here allows route planning before the trip, predicts travel time on different points of sail, allows comparison of the optimal tacking routes, and also plots the different routes so that it is inherently obvious that a particular tacking angle is longer and more off-course but will arrive sooner because of the speed on that heading. These principles can be implemented with manual dials that define the distance and speed, to calculate the relative or actual travel time on a leg without using electronics. Software is also described that visually illustrates the current and optimal headings by calculating Tacking Time to Destination before departure.

Claims

1. A method for comparing tacking distances and speeds in sailboats, said method including:

a) an estimate of additional distances entailed by tacking;

b) an estimate of boat speed on tacking legs;

c) an estimate of Tacking Time to Destination (TTD) based on the distance divided by speed;

d) an assessment of the optimal route to minimize the Tacking Time to Destination based on the tradeoff between distance and speed with the smallest quotient for travel time.

2. The method of defining the optimal Tacking Time to Destination in claim 1, wherein a ranking of the optimal relative course can be determined from only information on wind angle and bearing to destination.

3. The method of defining the optimal Tacking Time to Destination in claim 1, wherein a precise estimate of Tacking Time to Destination in hours and minutes can be defined if additional data on boat length and linear distance to destination is available.

4. The method of defining the optimal Tacking Time to Destination in claim 3, wherein estimates of speed and distance can be calculated for both the current route and the optimal route.

5. The method of defining the optimal Tacking Time to Destination in claim 1, wherein a function or look-up table is used to estimate percent of hullspeed on different points of sail based on either general polar velocity plots or specific polar plots for a particular boat.

6. The method of defining the optimal Tacking Time to Destination in claim 1, wherein a trigonometric formula is used to define the distance, which is Leg 1=D′

*sin (a+w)/sin (pi−

2a) and divides this by the speed on Leg 1 to get the predicted time for Leg 1.

7. The method of defining the optimal Tacking Time to Destination in claim 1, wherein a trigonometric formula is used to define the distance on Leg 2, which is Leg 2=D*sin (a−

w)/sin(pi−

2a) and divides this by the speed on Leg 2 to get the predicted time for Leg 2.

8. The method of defining the distances to travel in claim 6, wherein the distance on each leg is divided by the speed on that leg, with sum of the resulting quotients giving the overall Tacking Time to Destination.

9. The method of defining the Tacking Time to Destination in claim 8, which can be assessed for each different possible tack in order to choose the route with the shortest Tacking Time to Destination.

11. The method of defining the optimal Tacking Time to Destination in claim 1, wherein dials are turned manually to indicate the angles to the wind and to the destination, to make relative predictions about the route with the optimal Tacking Time to Destination.

12. The method of defining the optimal route by manually adjusting dials in claim 11, wherein numbered scales are added on the dials for distance and speed that indicate speed and distance values that can be used in a quotient to predict the optimal heading for the current leg.

13. The method of defining the optimal Tacking Time to Destination in claim 1, wherein the current and optimal tacking legs are displayed on a GPS chartplotter showing the two routes, the distances, speeds and travel times (TTD) for each.

14. The method of displaying the optimal and current tacking routes in claim 13, wherein the two different routes are coded by color or some other difference in style, along with numerical and text data to allow easy visual comparison between the current and optimal route.

15. The method of displaying the current and optimal tacking routes on a GPS chartplotter in claim 13, wherein the legs on each tack can be symmetrical or not, with the data for each leg shown separately.

18. The method of defining the Tacking Time to Destination for the current and optimal routes in claim 1, wherein possible routes are displayed on aerial photos, chartplotters or schematic diagrams to show distances or relative distances, sailing angles and speed on different points of sail.

19. The method of displaying the current and optimal Tacking Time to Destinations in claim 18, wherein plotting the routes makes it inherently clear that although a particular tacking angle is longer and more off-course, it would be predicted before even starting to have a shorter travel time because of the speed on that heading.

10. The method of calculating the Tacking Time to Destination in many possible tack headings, in which an algorithm can be used to reduce the number of calculations, by calculating TTD in larger intervals before narrowing in for iterations with more specific routes once the intervals with the smallest TTDs are obtained.

16. A method of determining the tacking time to destination before a trip, using convenient distance predictions and speed from existing polar plots.

17. The method of determining tacking time to destination in claim 16, wherein existing data on wind direction and polar plots are used to predict speed rather than requiring actual boat movement to determine velocity made good by trial and error while in transit.

20. The method of calculating tacking time to destination before a trip in claim 16, wherein predictions of speed, distance and travel time can be displayed for the current route in comparison to the optimal route for an obvious and convenient assessment before the trip.