VMG – Velocity Made Good
When sailing an asymmetric boat downwind it is not good to even think of a particular angle; the boat will be “snaking” all the time. With pressure in the sail, you can sail low, and with low pressure you must sail high. You’re continually heading up and down, using the information from the trimmer about the pressure in the sail. If the sail pressure is light and you head down too much the sail collapses, the boat slows dramatically, and you have to head up even higher to fill it up again.
It is important to develop a feel of when to change modes between high and low. Get a sense of it by sailing your polar boat speeds, remembering that as you go faster you can go deeper and deeper whilst maintaining that boatspeed. Use the speedo; as long as speeds are increasing you can go deeper. As soon as they level out or go down, point the boat up. The speed changes have to be at the slowest rate possible.
In a light easily planing boat such as the Melges 24, the angles change quickly with puffs and you have to steer to the pressure. Keep a slight curl on the spinnaker. In big breeze get the boat on a plane and go 5 knots faster. In heavier boats the angles/speeds are more similar—more like a spinnaker.
In the light sport boats, when it comes to angles, planing is the most important thing.
In a marginal planing boat like the J-80 you go as deep as you can until you go over 7.5-knots and as soon as you hit that, you turn the boat up 25 degrees, it will pop up on a plane, and then you’re planing at 11.5 knots.