GB2171208A

GB2171208A - Apparatus for analysing sailboat performance

Info

Publication number: GB2171208A
Application number: GB08503858A
Authority: GB
Inventors: John James Morven Scarlett
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-02-14
Filing date: 1985-02-14
Publication date: 1986-08-20
Also published as: GB8503858D0

Abstract

The performance of a yacht is monitored by measuring the apparent wind angle and the magnetic heading by suitable means 1,3, and determining the true wind angle from these measurements. The apparent wind speed and boat speed are also measured by suitable means 2,5, and these measurements are used to determine the true wind speed. The wind pressure is then determined from the true wind speed and the ambient temperature measured by suitable means 4. The calculated values for the true wind angle, the boat speed, and the wind pressure are supplied to a processor 9 which determines the maximum boat speed for each of a series of wind angles for various values of the wind pressure. The data resulting from such processing is supplied to a polar plotting device 10 which plots a series of polar graphs of maximum boat speed against wind angle. <IMAGE>

Description

SPECIFICATION Apparatus for Analysing Sailboat Performance This invention relates to apparatus for analysing the performance of a sailboat, and particularly that of a racing yacht.

It is becoming increasingly important in the field of yacht racing to maximise the performance of a yacht for a given wind speed and apparent wind angle, that is the angle of the wind direction relative to the heading of the yacht. In order to assess the design and performance of a yacht under varying conditions, it has been proposed that series of measurements of boat speed, true wind speed, and apparent wind angle should be taken with various sail settings during actual trials of the yacht, and that these measurements should subsequently be used to manually plot a series of polar graphs of maximum boat speed against true wind angle.In practice, provided enough measurements are available, each graph will form a curve indicative of maximum boat performance at a particular wind speed and in particular water conditions, and a series of such graphs may be produced to provide an indication of the overall boat perofrmance under different sailing conditions.

However, performance graphs produced in this manner have been shown to have limited use since other parameters render the results inconsistent.

It is an object of the invention to provide a more reliable arrangementforassessmentofsailboat performance.

According to the invention, there is provided apparatus for analysing sailboat performance comprising wind pressure determining means for obtaining a value substantially proportional to the wind pressure from measured values of the wind speed and the ambient temperature, and indicating means for indicating the variation in boat speed against measured values of the wind angle for a particular value proportional to the wind pressure as determined by the wind pressure determining means.

The apparatus preferably also includes one or more of wind angle measuring means for monitoring the wind angle, temperature measuring means for monitoring the ambient temperature, and wind speed measuring means for monitoring the wind speed.

In a preferred embodiment of the invention the indicating means is a polar plotting device for producing a polar graph of values of the boat speed against various values of the wind angle. Performance graphs produced by such apparatus have been found to be considerably more reliable in practice than performance graphs produced by the known technique. Furthermore the apparatus may be adapted to be installed on the boat so that the polar graphs may be plotted and evaluated on board during the trials, without it being necessary to collect the data measured on board and process this on land as has previously been the case.

The invention also provides a process for analysing sailboard performance, comprising determining a value substantially proportional to the wind pressure from measured values of the wind speed and the ambient temperature, and indicating the variation in boat speed against measured values of the wind angle for a particular value proportional to the wind pressure.

In order that the invention may be more fully understood, a preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, in which: Figure lisa diagrammatic representation of the apparatus; and Figure 2 is an example of a polar graph produced by such apparatus for a particular wind pressure.

Referring to Figure 1, the illustrated apparatus, which is adapted to be installed on a yacht, comprises a masthead wind unit including a wind angle detection system 1 for measuring the apparent wind angle and an anemometer 2 for measuring the apparent wind speed, an electronic compass 3 for measuring the magnetic heading, a temperaturesensitive device 4 incorporating a thermocouple or thermistor for measuring the ambient temperature, and a log impeller unit 5 for projecting beneath the boat hull for measuring the boat speed.

The outputs of the detection system 1 and compass 3 are supplied to circuitry 6 for determining the true wind angle, and the outputs of the anemometer 2 and the log impeller unit 5 are supplied to circuitry 7 for determining the true wind speed. Circuitry 8 serves to determine the wind pressure in dependance on the outputs of the components 4 and 7 respectively proportional to the ambient temperature and true wind speed.

The wind pressure may be considered as being proportional to p V2 where p is the air density and V is the wind speed. The air density is dependant on the humidity and temperature of the air. However, it is believed that variation in the humidity of the air can in practice be ignored, so that the wind pressure may be considered as being proportional to V2/T where T is the temperature.

The outputs of the components 5, 6 and 8, which are respectively proportional to the boat speed, the true wind angle and the wind pressure are then supplied to a processor 9 which determines the maximum boat speed for each of a series of wind angles for various values of the wind pressure. The data resulting from such processing is supplied to a polar plotting device 10 which plots a series of polar graphs of the type shown in Figure 2.

Referring to Figure 2, the polar plotting device 10 plots for each value of the wind pressure a polar diagram 11 in which the angle of each point of the plotted curve 12 with respect to the origin 0 corresponds to the apparent wind angle associated with that point and the distance of the point from the origin 0 corresponds to the maximum boat speed for that wind angle. A series of such polar graphs are produced by the polar plotting device 10 for various values of the wind pressure, and these provide an accurate indication of the boat performance.

The components 6,7,8 and 9 may be combined in a single unit and may be constituted either by discrete electronic circuitry or by a suitably programmed computer.

The apparatus may be used not only to provide an initial assessment of optimum boat performance during trials, but also to give a continuous indication of performance during normal sailing which may be compared with the polar graphs indicating optimum boat performance. The polar graphs produced by the apparatus may be used for sail evaluation and to determine the particular sails to use to reach the maximum boat speed in particular conditions of wind speed, wind angle and temperature. Such evaluation can be used as an aid to sail design and to prevent the use of sails outside the tolerances recommended by the sale manufacturers. The polar graphs may also be used to evaluate tacking and gybing efficiency under varying conditions.

Claims

1. Apparatus for analysing sailboat performance, comprising wind pressure determining means for obtaining a value substantially proportional to the wind pressure from measured values of the wind speed and the ambient temperature, and indicating means for indicating the variation in boat speed against measured values of the wind angle for a particular value proportional to the wind pressure as determined by the wind pressure determining means.

2. Apparatus according to claim 2, which also includes wind angle measuring means for monitoring the wind angle.

3. Apparatus according to claim 1 or 2, which also includes temperature measuring means for monitoring the ambient temperature.

4. Apparatus according to claim 1,2 or 3, which also includes wind speed measuring means for monitoring the wind speed.

5. Apparatus according to any preceding claim, wherein the indicating means is a polar plotting device for producing a polar graph of values of the boat speed against various values of the wind angle.

6. Apparatus according to any preceding claim, which is adapted to be installed on the boat.

7. A process for analysing sailboat performance, comprising determining a value substantially proportional to the wind pressure from measured values of the wind speed and the ambient temperature, and indicating the variation in boat speed against measured values of the wind angle for a particular proportional to the wind pressure.

8. Apparatus for analysing sailboat performance, substantially as hereinbefore described with reference to the accompanying drawing.

9. A process for analysing sailboat performance, substantially as hereinbefore described with reference to the accompanying drawing.