Your set Boat Polars are either Predefined, Sail or Advanced.

Having it set at 100% reflects your set sail polars, however you may wish to adjust these polars.

For example setting the polar speed adjustment to 90% will take 10% off your set polar speeds for your next weather routing download.

Useful for say when you reef your main before night fall to be prudent, or perhaps towards the end of a long passage and the boat is not so heavily laden and performing better you could set it at 110%.

The Polar Speed Adjustment is also useful if we do not have your sail boat in the Predefined polar list. Selecting a similar boat and using the Polar Speed Adjustment is a good option.

Download a Sail Route, check the results in the WIND tables, check to see if the results look reasonable for the performance of your boat. Does the speed of the boat look okay for that particular wind angle and wind speed? If not use the Polar Speed Adjustment, download another weather route and check the results again.

The Night Time Adjustment is applied on top of the upwind/ downwind adjustment and allows the router to take into account that you sail the boat slower / with less sail at night for safety reasons. This value will be added on top of any other Polar Speed Adjustments you have applied.

On the Forecast Website select Weather Routing from the main menu then select Sail Routing. Open the Routing Preferences Tab