Velocity Made Good (VMG)
If you’ve been reading my posts on Sailboat Racing, you have probably figured out that in sailing, you very often wind up going not going straight at the place you want to arrive. Even when cruising, there is a measure of “cautious” navigation that may over-correct for leeway or current when attempting to make landfall on a shore that is out of sight. So you will often here sailors talk about maximizing their “VMG” or Velocity Made Good.
Velocity Made Good, simply put, is the speed at which you are traveling toward your destination. As we have said, you don’t always point towards your destination so it is often something less than your speed over ground. There are some trigonometry calculations that can calculate it, and while trig was one subject in math I was good at, I don’t want you to stop reading, so I’ll just say calculating your VMG has to do with triangles and vectors and any good Chartplotter should have that information available.
There are optimal sailing angles to maximize your speed based on your boat’s performance in various windspeed conditions. They are plotted on something called a polar diagram. This is especially important in downwind sailing and even more so with some of the new sport-boats with asymmetrical spinnakers. Knowing at what wind speeds to soak down towards the mark versus what wind speeds to keep the bow up higher in the wind and go faster, even if it is not as direct a route, is the difference between first and worst. That, coupled with the wind direction, also affects how you use the racecourse on the downwind.