In the game Virtual Regatta, we can program headings, either manually, either using Expert mode (programming) or with the routing option. Headings can be, either in compass mode (default mode), either in wind mode, by activating the lock in the interface. This is the "autopilot wind control" mode well known by sailors in real life.
Weather4VR integrates this system into its routing module, by differentiating the legs to be made in compass mode (HDG for Heading) and those to be performed in wind mode (TWA for True Wind Angle). This last mode is preferred as soon as the routing plans to tack (tack upwind) or perform gybes (tack downwind) in order to adopt the best wind gain angle, the famous VMG (¹). It maintains a constant angle with the direction of the wind.
Once the routing is performed, and of course according to the direction to follow and the different directions of the wind to meet, the programming points to be exported into the game will be HDG or TWA points. These will be indicated with the angles respecting the speed polar included in the game., and therefore the angles of maximum VMG deduced from this polar. In the interface Expert we can visualize these angles of VMG max, which differ according to the wind speed and the sail set used.
In Weather4VR this results in a programming table, and of course the plot of the calculated legs on the map. The heading HDG is followed by the letter T for True (true heading = geographic) and the TWA heading is followed by the letter S for Starbord (tribord) or P for Port (port).
Do not confuse the TWA legs of the programming which are indicated with the angle of the selected VMG, and the heading on the map resulting from this mode :
You will notice that the dotted lines showing the actual track made by the boat reproduced from the game interface, may differ slightly from programming. Actually during successive updates in the weather forecast game (16 times a day) there may be fluctuations in wind direction and strength. This changes the route performed since in TWA mode we keep a constant angle with the wind.
And for any questions regarding the use of Weather4VR join the Facebook group of Weather4VR users. You can learn much more !
(¹) See article VMG / VMC for dummies