Sailing Performance Trials - 2018

This page, and the pages sitting below it, contain information about and access to the results of the JRA Sailing Performance measurement project. To see the history of this project, please look at the Performance Measurement thread on the Technical Forum or the article(s) in the Magazine.

So far (2020) we have run trials on seven boat and rig combinations. Details of these boats can be found on the page "Details of Tested Boats"

Polars comparing the performance of the seven boats tested so far can be found on the "7 boat polars smoothed" page.

Polar diagrams for each boat and rig combination tested, using the average of the three highest speeds recorded for each wind speed and angle, which have been created by Anthony Cook, can be seen on the pages for each boat below this page and more are stored on Dropbox here. 

There are separate Excel spreadsheets with the calculated results for each boat and rig combination tested which can be downloaded from Dropbox here.... (the Dropbox files are currently being updated) On these spreadsheets you can see the smoothed and unsmoothed polars, and the comparisons between the smoothed and unsmoothed polars at each wind speed, and also port and starboard tacks superimposed for each wind speed.

The raw data from the trials can be found here. 

The raw data is available in the following formats
1/ as .txt files containing the NMEA sentences from the wind and water sensors recorded during the trials
2/ as .csv files containing the boat speed and apparent wind speed and direction every second

In the data folders are separate files for each test run and for port and starboard tacks. There are up to 8 runs on each tack for each boat. To simplify processing the text files to produce polars in Polauto, the data files for each run on each tack on each boat have been combined into a single file called "Name of Boat P (or S) combined". In combining these files any NMEA sentences before the first boat speed sentence have been deleted to prevent wind data from one file being used with boat speed data from another file. The deleted data would not be used anyway as there is not boatspeed value for it to be used with.

Polar Diagrams using the Median Boat Speed  and True Wind Speed and Direction can be seen on the page "Polars (Median Boat Speeds)". These were created by Robert Self from the .csv raw data files.


This next section is in the process of being updated with 2020 information.     

In the data files on Dropbox there are separate polar folders for each boat tested. In some there are additional folders for trial polars that were produced while testing various filter options in Polauto. Ignore those unless you are interested in the effects of different filters. 

In the main folder for each boat there are polars produced from the unfiltered raw data, and another set of polars produced using my selected set of filter options, and a correction factor to adjust the boat speeds for waterline length and for sail area to displacement ratio. These filtered and corrected files contain the words "JRA filters & corrn" in their file name.

I concluded that the polars need editing to smooth the rather spiky curves for each wind speed, and to remove data for 2kt and 4kt windspeeds, which produce very erratic results and are of little relevance. This editing and smoothing has now been completed and is shown in the polars.

This editing is done following a set of rules as follows:

1/ When filling in dips or removing spikes in the polar the boat speeds would be interpolated in a linear fashion both along the windspeed curve and across the set of windspeed curves to create a fair curve between the points where the dip or spike starts and finishes.

2/ Where there are only a few points for a wind speed, they would be deleted.

3/ That data for apparent windspeeds of 2 and 4kts would be deleted as the accuracy is very dubious.

4/ Where necessary the fairing would tend to make the curves conform to the expected shape of sailing polar curves, that is to say, boat speed falling off when too close to the wind, and increasing on a close fetch and reach, and decreasing slightly near a dead run.

If you want to compare several polars at the same time, I recommend using Faststone Photo Viewer which is available to download free here It allows you to view up to four images at the same time.

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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