Does the main fit the mast?

by Steve Hunt, Sailing World
Hang out on the docks long enough and one topic you’ll hear plenty of is mast and mainsail fit; whether the luff curve is correct for the mast or the mast is set up correctly for the mainsail. There’s much to consider in order to determine if things are as they should be, but it all starts with knowing what to look for.

I remember Kevin Burnham (two-time 470 Olympic medalist) telling me that you want the mast to be smoothly curved, like a bird’s wing, where there are nice transitions between one part and the next. It’s the same with a sail, and a great way to see the transition is with draft stripes. When you look at the three draft stripes on your mainsail, you want them to have a similar shape as they start at the mast and smoothly transition into the body of the sail.

There is typically a small variation in each stripe from top to bottom—getting flatter or fuller as you go—and that’s normal, but you don’t want any one stripe sticking out as an anomaly. Depending on the boat you’re sailing, and the conditions in which you’re sailing, the stripes may get fuller or flatter as you transition toward the head of the sail.

For example, with an Etchells mainsail, in light air you might want power up high with a flatter section down low to open the slot between the back of the mainsail and the jib, which means you’ll see the bottom stripe fairly straight off the mast, the middle stripe a little deeper, and the top stripe deeper yet. – Full Story.