Today, Mike McNamara was invited to talk at the club on Racing Tactics. He is really good in explaining things, he is definitely very experienced and he has a way to make things sound funny, so the whole talk was quite enjoyable.
He talked about upwind and downwind sailing, mark rounding and he had some slides that were showing how the air flows around the sails. It wasn’t a simple drawing with arrows showing the airflow. They were computer generated (I guess) with some modeling software using wind-tunnel data, or something like that. You could actually see wind threads and the tiniest turbulence caused by the sails.
He also mentioned that for boats that has only a mainsail, that sail behaves like a jib. That is quite interesting and I hadn’t thought about it. But as he showed it on the slide, he was right. As the wind hits the jib at an angle of let’s say 45 degrees to the centreline, at the leech of the jib the wind has curved around. So the wind hits the leeward side of the mainsail at a 35 degree angle. In a single-sail boat the wind comes clean and will have to hit the sail at the same angle as it hits a jib.
He also made vary clear the rule on mark rounding when a boat has established an inside overlap as it enters the two boat lengths circle around the mark. He even gave some notes to be uploaded to the club’s website.
Overall, it was quite interesting, and I think everybody enjoyed it. I really need to find some time to put all these in my mind in the right order.