Project Description

Polar diagrams
A polar diagram shows you the boat speed for a given true wind speed and true wind angle. This is important for routing programs, that calculate the best course for you to follow and the ETA for a given wind prediction. For the speed addicts, it is good to know if you are sailing the optimum speed. The simple polars from Foutaine Pajot are based on theorethical models, light ship. That means ideal sails, clean hull, no waves, no food, no accesssories, no options, no spares, no food, no clothes and worse: no wine.

Over the last two years I have been gathering real data to get more realistic polars for our boats. There are several problems that I needed to eliminate:

  • Current. Since the Boatspeed through te water is very inaccurate, I prefer to use GPS speed. But that is only useful when there is no current/tide.
  • Waves. I tried to collect data mostly in sheltered waters
  • Wind Shear. Sometimes the wind angle can be very different high up the mast than lower down. From my racing days I know we have seen differences of 15-20 degrees!
  • Stable wind. On a puff it takes some time for the boat to pick up speed and other way around. Sometimes it is hard to pick a fair number.
  • Calibration of instruments. There are two major calibrations. Boat speed through the water and wind angle. In Garmin you can only calibrate for one speed. For example 7 knots. Not only is the speed different on each tack, but the calibration is not linear. So it may be good at 7 knots but then a knot off at 9 knots.
  • New sails added, Spinnaker pole added

The attached polars are based on the sails I have. The selected sail for each wind is shown too. I don’t have to think which sail to hoist anymore. It does not mean the boat cannot go faster. It is just what I feel comfortable with. A little bit of data is missing but there is so much available that it is time to share it with you. Spinnaker speeds are still based on ‘no spinnaker pole’ data. Good for most of you, but I need to add quite some more speed for angles > 150 degrees. Also, the data of my new Code zero is not included yet. So my speeds around 80-110 degrees true will go up quite a bit too for winds upto 15 knots. Feel free to compare it with your own sail set up and modify it accordingly. It is a great tool to have.

Sails:

  • Screacher 120m2. Incidence
  • High Tech code zero 120m2. Sail Design. (Values not yet included in polar)
  • Gennaker / Asymetrical spnnaker 165m2. Incidence
  • Symmetrical spinnaker 165m2. Sail Design (data based on sailing without Spinnaker pole.

Download the excell polar data by clicking on this link:  >Saona Polar<