Reefing and wind

Reefing and wind
Vingilótë’s helm. Almost all lines are brought back to the helm so it can be handled by one person, in a pinch.

So a bit of sailing technobabble. If you’re already familiar with sailing jargon you can ignore this post.

One thing about sailing is that too much wind is worse than not enough wind. Not enough, and you just don’t go anywhere. Too much, and you can damage your boat, up to and including turning it over, which is seldom a good plan.

But when you’re on long trips, sometimes the wind changes it goes from not enough to too much within minutes sometimes. So, long ago wise sailors invented ‘reefing’. Also sometimes known as ‘shortening sail’ Reefing basically means you lower your sail a bit down the mast, bunching up all the excess sail at the bottom, so you have less surface area of sail to catch the wind. This makes the boat easier to control, less likely to capsize or break something.

Vingilótë has three ‘reef points’ which are lines attached to the back of the sail so you can keep the bottom of the reefed sail tight. Tonight as the wind crept up into the mid 20s we decided to go to the second reef point. This takes the mainsail from its normal 106.7 square meters down to 65.21 square meters. We can go farther: the next reefing point would take it down to only 39.08 square meters. If the apparent wind goes over 30 kts we’ll do that.

While I’m on the subject, about wind. There are two types of wind that matter to a sailboat: true wind and apparent wind. So what are they?

True wind is what the local atmosphere is doing relative to the earth. Apparent wind is what it’s doing relative to your boat. Examples.

If you’re standing perfectly still on the dock, and the wind is blowing 10 kts in your face, that’s 10 kts true wind.

If the air is dead calm, no breeze at all, but you’re standing on the bow of a boat moving at 10 kts, then you feel 10 kts apparent wind in your face.

If there is 10 kts of wind at your back, and your boat is moving forward at 10 kts, you will feel no breeze at all. That is zero kts apparent wind.

If the true wind is blowing 10 kts in your face, and your boat is moving you forward at 10 kts, you’ll feel 20 kts apparent wind in your face. Make sense?

This becomes very important because your angle relative to the true wind, and your speed, directly influence how much apparent wind you have. It’s geometry.

(BTW, speed over water is measured in kts, short for knots, nautical-miles-per-hour. A nautical mile is one minute of latitude, or a little over a mile.).

One comment on “Reefing and wind
  1. Very clear; missed your calling. Should have been a teacher!
    All very interesting stuff for the lay persons following Vingilote. Thank you.

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