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Use of mainsail

3534 Views 12 Replies 10 Participants Last post by  pdqaltair
After watching a lot of cruising youtubes I find that a lot of people sail with just a jib or a combo with a deeply reefed main. Is this really that common?

Is there a narrow window of wind speeds that merit the use of the main?
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You ask two questions.

Yes, people will sometimes use the the genoa. Sometimes for convenience, sometimes when blowing. With just the genoa beware of lee helm. We don't get much lee helm but it can happen depending on boat and sails. In extreme conditions, only a storm jib will be flown.

Is there a narrow window of wind speeds that merit the use of the main?
No, not at all. On our boat, upwind it goes something like this with a LOT of variation (before everyone jumps on me for the exact wind speeds & combos):

0-15 kts: full 145% genoa, full main (adjusting main & genoa shape as wind increases)
15-18: full genoa with the top opened, single reefed main
18-20: 130% genoa, single reefed main
20-24: 130% genoa, double reefed main
24-28: 110% genoa, double reefed main
28-30: 80% genoa, double reefed main (with a lot of bleed off)
30-33: 50% genoa
33+: run off

The idea is to keep the boat as flat as possible with whatever sail combination works. There are no hard and fast rules here. On our boat, we don't like to heel more than 23 or 24 degrees. After that, we're real slow even if it seems more exciting. You can see similar boats walk past us when we sail at greater angles of heel. And then there's the leeway that become preposterous... and the weather helm too, which is like driving with the brakes on. Not accounting for wave action, if you need more than a couple of fingers on the wheel or tiller, your sails need attention.

Keep in mind that with a roller furled genoa, performance degrades significantly as it's rolled up. This is because the shape is designed for 145% (in our case) which means that it's pretty full (meaning that it has a lot of lift), which is what you don't want when the wind increases - you want flatter (less lift). So when it's rolled up, you just have a smaller, too full genoa. In perfect world or on a racing boat, the smaller sails will be increasingly fatter. We had our genoa built somewhat flat in hopes that it would carry into the greater wind speeds better. In practice, it sucks in light air and is too big in heavier air. It's probably going to be augmented with proper light air 155% for summer doldrums and light air racing. Think of airplane wings - a slow piper cub has fat wings with a lot of lift. An F-16 has skinny wings with less lift (because the greater speed will generate enough lift)
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