We have seen them often. A collection of circles with a strange looking graph overlaid. One axis seems to represent wind strength and the other speed of the boat. But there is more to these polar diagrams especially of catamarans. Let’s look at them in depth:
The circle at the outside marks the TWA (True Wind Angle) angle to the course of the boat which is virtually situated in the middle of the diagram. The angle tells the direction of where the true wind is blowing. Starting in the middle and concentrically moving outwards are circles marking the speed of the boat (in knots). Typically, these diagrams are calculated using a VPP (Velocity Prediction Program) – a highly complex calculation taking algorithms and boat data into account. Usually polar diagrams calculate boat speed using only working sail – meaning only full mainsail and Genoa, or jib. Adding a special downwind sail such a Code-0, Gennaker or spinnaker substantially increase speed from a close reach to a near run. This is especially true for catamarans as a large component of the wind felt by the sails is the apparent wind generated by the boat itself.
If you want to know more about polar diagrams and how to interpret then we would be happy to help you.