I have also just acquired a Garmin GPSMap 76CSX. I am still figuring it out - its a great GPS, but the documentation is pretty basic. I think I have the VMG figured out.
I've been able to get the VMG speed to reach the ground speed, should I be able to exceed to ground speed?
- VMG cannot exceed ground speed, since for any given ground (or water) speed
, the fastest you can approach your destination is to head straight for it, in which case, ground speed will equal VMG.
how do you have your GPS display setup when you view VMG
I have set up my trip computer page to display VMG - I believe you can do the same on the compass page.
how do you adjust course heading to optimize your VMG speed?
The whole point about VMG is that the maximum speed through the water is usually not the fastest way to reach your destination - there is usually a tradeoff. VMG is the speed at which you are actually approaching your destination. The AI usually reaches its maximum water speed on about a beam reach (around 90 degrees to the wind), but the shortest distance to your destination is more often than not at some angle other than this. If your aim is to reach your destination as quickly as possible, the trick is to adjust your helm (angle to the wind) until you achieve the highest possible VMG reading. For example, if you are sailing on a close reach and you start to turn away from the wind and the VMG reading drops, you should point higher into the wind, even though your boat speed may drop. If your VMG reading increases, you should gradually point higher until your VMG starts to drop. Whichever heading gives the highest VMG is the optimal heading for reaching your destination quickly.
To make things even more complex, you need to adjust the trim of your sail whenever you change your heading, so you should compare the VMG reading after
you have trimmed the sail.
Personally, I'd rather take a bit longer and have fun with the boat moving faster