Playing the Shifts
In order to sail the beat as quickly as we can we need to keep the best average VMG that we can. In this blog we will discuss the influence of shifts on our VMG and the use of a compass to improve our tactical decision making.
The faster the boat, the more influence a gust or pressure increase will have in what is termed a velocity lift – a lift caused by increased pressure. In a Laser, we will typically see a 5 to ten degree height gain with increased pressure. In a this will be doubled.
A part of the skill of sailing is identifying whether we are being lifted or headed by velocity change or by a shift. In theory this is simple to spot as we have to hike differently or trapeze harder and the rig loads up or goes easier. In practice the small velocity changes can confuse the situation, so conscious practice is needed to differentiate between a velocity or angle shift.
As a general rule most shifts that you feel whilst sailing a boat such as a Laser will be angle shifts. Most that you feel whilst sailing a fast boat such as a skiff will be velocity lifts. That’s a dangerous generalization if taken to the letter, so please understand that it is a guide, not a rule.
Using the compass
Although there are many methods to tell the shifts the most accurate and reliable one is the use of a compass since it is the only available tool that gives us an accurate bearing of our course.
Important note: In order for the compass data to be accurate it is crucial to sail the boat according to the tell tales on the sails, luff telltales in single sail boats and jib telltales in doubles. While sailing the boat according to our telltales and not according to the shifts we ensure the flow on the sails remain optimal and keep our boat sailing at her best possible speed and height to our settings.
The very basic use of the compass is to take the bearing sailing upwind in both tacks for a long enough duration of time, this will ensure we can read the lifts, headers and neutral angle of the wind in each tack as well as any wind pattern to the shifts and the duration of the shifts. Knowing what our course should be, and comparing it to what is happening now, leads to a reliable platform from which to make tactical decisions. We cannot only spot shifts, but we can also reliably identify if there is a trend to the movement of the wind, and what that trend is. That will play an important role in the decision of which side of the fleet to race in.
The accepted tacking decision is made when the shift goes to over a five degree header. This will shorten the course by a considerable amount. In some locations only the big shifts count, and through experience you can figure out which locations these are.
On the downwind for single sail boats that can sail by the lee the compass becomes almost irrelevant as it is not as crucial to sail the shifts since the boat has the ability to sail in different angles. In spinnaker boats the lowest angle is determined by the collapsing spinnaker so knowing the angle to the mark through reading your compass it becomes important to take notice of the figures and minimize the risk for the lay-line decision.
There is so much valuable data to be gained from the compass, so that unless you are a world class sailor in an environment where there are plenty of transits to be taken, it becomes a critical tool of success. During our training at TopLevel sailing we work with our sailors on both basic and advanced use of the compass incorporated with improving their prioritizing skills in order for them to maximize their performance.