How it is computed
The speeds are computed as in the eSail4VR app and in the game: each sail’s speed grid, interpolated between the wind and angle points, then the effect of the foils (which depends on the wind and the angle) and that of the hull polish.
VMG (Velocity Made Good) is the useful speed towards the wind or away from it: it is what counts upwind and downwind. The two red lines mark the best VMG angles.
The gain shown next to each option is the one at the chosen point (wind and angle), with the other ticked options.
The Which sail, and how far? section shows, for the chosen wind, the angles where each sail is the fastest and those where the game still keeps it: it changes sails only when another is faster by at least the boat’s tolerance (1.4% for the boats listed here). The zones are computed with eSail4VR’s rule and the sails ticked; foils and polish do not change them.