VMG

The importance of Velocity Made Good towards the mark in Boat Racing

Whether sailing upwind or downwind, the boat must sail at an angle to the mark to ensure airflow over the sail and the best speed possible. The angle to the wind that is sailed means that we have to calculate or judge the real speed of the boat towards the mark, usually choosing the best tack in order to achieve the best VMG. The term velocity made good is very relevant to success in racing – the boat with good VMG may in fact be slower through the water than the boat with bad VMG, but will win because it is choosing the shortest route to the mark.

Here is an illustration of good and bad upwind VMG:

VMG or Velocity Made Good is the term used to measure how fast a boat is approaching her mark or target, it involves both the angle the boat is sailing towards the mark and her speed, both might vary largely during a beat or a run. In theory we can very accurately measure our boats VMG, however since we are not allowed in dinghy racing to use the technology to do so we must learn how to estimate our VMG or use methods to ensure we keep as good VMG as possible throughout the race.

Speed influences VMG, but angle to the wind is the essence of understanding and using VMG and using it to win races.

There are 3 major aspects that will affect our boats VMG:

1. Shifts – which influence the angle we are moving relatively to the mark.
2. Pressure – which influence our boat speed regardless of tuning
3. Current – which influence both the angle our boat will move and the speed depending on the direction

We also have boat drift however it is a very minor factor for dinghies

How shifts influence our VMG?

We all know that taking a header will mean our boat has to sail an extra distance to the mark and taking a lift means we are taking a short cut. Many sailors don’t even begin to recognize how destructive taking a header might be. For example in this diagram we will show that a 15 degree shift will double a boats VMG (the one taking the lift) relatively to the other boat (that will be taking a header) , you can easily do the math and calculate how much a single degree is worth to your VMG

How does the pressure affect our VMG?

Simply by changing our boat speed, We all know that in a gust our boat goes faster and in a wind hole it will go slower, as sailors we have the ability to avoid wind holes or sail into gusts, the trick is to be able to sense and estimate what is the speed difference to our class of boat and given conditions. This will basically help us to prioritize and decide how big of a header and for what distance is worth to get into the gust. Remember we want to keep the best average VMG over the entire leg.

How does the current affect out VMG?

Current will either push our boat towards the mark or away from the mark. Depending on the direction of the current and which phase of the leg we are on. In some places there will be a difference between different areas of the race course in both current speed and direction. Those differences might prove very beneficial if we know to to use them to our advantage.

We have discussed observations substantially in a previous blog, collecting enough information will allow us to build a mental map of the race course and decide which areas will have an influence on our VMG, all to assist us we reaching the mark as fast as we can.

In Toplevel sailing we train our sailors how to estimate and prioritize those different factors and use it to their advantage.

Want to learn more? Come and join our training camps!