Is there a software to analyse the polars of a boat?
Post by iconPost by Ptit Pimousse | 2022-05-10 | 13:46:39

Hi everyone,

I have a question which maybe a bit tricky. I ahve noticed on the Imoca that sometimes the polars will allow you travel faster at low wind vs higher wind and the then reverses at much higher wind.

example of that:

TWA50 @ 12.4 knots = 10.83
TWA50 @ 14.4 knots = 10.67
TWA50 @ 15.4 knots = 10.67
TAW50 @ 16.4 knots = 10.77

basically you need 17.4 knots of wind in order to travel faster than at the lower winds. Which leads me to a question. Aside from going through the polar chart and look for these interesting variations, is there a software or a method to analyse these polars in a format which allows me to identify these faster?

Thank you

commenticon 6 Comments
Post by iconPost by BooBill | 2022-05-10 | 18:08:39
qtVlm has a polar view with an option to see all the polar curves at the same time. If they are not concentric, it's pretty obvious.
Post by iconPost by toxcct | 2022-05-10 | 20:22:28

Yes, there is another way.
You can hit my polars generator (, select your boat sails and options, and then spot the array.
you have "almost" all the values at once in this 2 dimensional array.

For instance, on the class40, with a full pack, here what we get:

That array doesn't show the higher speeds or the best sails at first sight, but you can copy/paste into Excel (or any decent spreadsheet app) and colorize the higher values (you might need to convert from ";"-separated rows, and maybe replace the digital separator as well):

Once you have that, you can spot that the higher speed is around 120° TWA, and 30 kts TWS. Then back to the polars generator app, you can hover over that cell and it will tell you which sail is best for thos conditions :

You can also use the polars chart to spot that:

2 caveats however:
- I did not use extrapolated values here for the explanation, but you should get better results.
- This does not lead to the best VMG; only the best speed, which is rarely the better option.
However, to get the VMG is pretty easy: use the first spreadsheet as your source table, and then build a second table that calculates the speed times the cosine of the TWA for each cell. The higher values, the bigger VMG:

Hope that helps ;)

Post by iconPost by toxcct | 2022-05-10 | 20:23:57
(EDIT: post modified and images resized)
Post by iconPost by toxcct | 2022-05-10 | 20:36:30

Post by iconPost by Ptit Pimousse | 2022-05-11 | 06:54:11
Wow that's complete! Thanks very useful.
Post by iconPost by fransou | 2022-05-11 | 08:21:43 it's a good Web site for you
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