Anyone starting out in sailboat racing will quickly learn the importance of start line bias and most sailors, most of the time will be pre-occupied with starting in good shape at the 'favoured' end of the line in the minutes leading up to the start gun as a good start goes a long way towards securing a good result. However, the 'favoured' end of the line might not necessarily be the end where the bias is.
Over the Easter weekend at the RORC Red Funnel regatta I was sailing on the Half Tonner ‘Chimp’ in IRC 4. On day 1 the wind had an average direction of 020 though being a North Easterly there were significant shifts either side of that number with the shifts becoming more pronounced the further up the beat you went, i.e. the closer you got to the shore. The start line was set more or less square to the average wind though clearly the bias on the line depended on which phase the wind was in.
So the big question was which end of the line to start at? The general strategy was to play the right hand side of the beat because all the forecasts were predicting the wind to slowly veer right as the day wore on. As our start time approached the wind was in the left meaning that there was a notable port bias on the line of around 15 degrees. I felt that was too much to give away so elected to start towards the port end on starboard with a view to getting onto port tack (the lifted tack) quickly. Although we executed a good start we unfortunately ended up with a slightly quicker boat on our windward hip which didn’t share the same enthusiasm as us for being on the other tack. By the time we did manage to get onto port we were on the left hand side of the beat and all of the main contenders in our fleet had gone the other way. The breeze had also now started to swing the other way meaning that we were now on the unfavoured tack on the unfavoured side of the course. We struggled to find clear air and struggled to get back in phase with the shifts and although we sailed the rest of the race pretty well we ended up a disappointing 7th from the 18 starters.
Conditions were similar for race 2 but this time we adopted a different strategy. Even though there was still a port bias on the line we decided that our priority was to get onto the favoured tack as a matter of urgency so that we were in phase with the shifts and heading to the correct side of the course even if that meant giving up the line bias. In reality the start line wasn’t that long so we weren’t giving up an awful lot of distance anyway. So, we started on starboard, on a header with nobody to windward of us, flipped immediately onto port tack and sailed for several minutes on the port lift before the next anticipated right hand shift came in. We tacked immediately and were able to cross the boats from the left that had taken the line bias. Now, perfectly in phase with the shifts, sailing in clear air and sailing in the best pressure we were second around the windward mark comfortably ahead of all the boats except one that gave us lots of time. In other words, in shifty / oscillating breezes the line bias was less important than being on the paying tack at the earliest possible opportunity and that factor would therefore dominate our starting strategies from then on.
So what were the other salient points from the day? Firstly, if the breeze was in the left, although there might be a few minor oscillations, the next significant shift would be to the right so it was important to position the boat accordingly to take full advantage of that when it happened. Secondly, try to get a feel for the timing of the big oscillations, how long did they tend to stay in for? Thirdly, when the pressure was up the breeze tended to be more to the left (the gradient direction). The breeze tended to go right in the sunnier spells when it was also a little lighter. Looking at the sky and the water further up the track provided some good indicators of what might happen next; if you needed a right hand shift, head for the sunny patch though bear in mind that the wind might be lighter there!
On days like this it is impossible to cover all the bases all of the time. On the first beat you need to be on the correct side of the first few shifts in order to take care of the bulk of the fleet. On subsequent beats when the fleet is more spread out you can use the shifts to pick off individual boats.
In summary, in deciding where to start, consider the line bias of course but also consider where you want to position the boat in order to take advantage of the next shift and get fully in-phase with the oscillations.