Sail in clear air is important but there are no automatic alarm bells for bad air. Some sailors also are not as sensitive as they should be about getting clear air. I have put together tips on clear air from my knowledge and online resources. We focus on upwind sailing for now.

What you should know:
⦁ Bad air zones around a sailboat
⦁ Typical upwind trouble spots
⦁ Ways to keep clear air
⦁ When to keep going in bad air

Bad air zones around a sailboat

First is the direct wind shadow of the sails causes called blanket zone. It is directly downwind to the sail so it extends to lured and behind the sailboat. If you have ever tried to sail through another boat’s wind shadow or blanket zone from behind. You have to know be several lengths away to have a chance.

Next, one is the backwind zone which is caused by the acceleration and deflection of the wind by the sails. This is straggly here with all sorts of vortexes swirling off the leech of the sail. Some sailors do not realize that the blanket zones extends a good distance to wind for the boat as well as behind. Another thing to note is that the sails deflect the wind from its original direction. So a boat on the same tack in the back winds zone will experience a header. This is why it is so difficult to hang with a boat on your lured bow.
There is the third zone that can have a big effect on light air sail. The sailboat is an obstruction to the wind just like a building a tree. So some air tries to flow over the top of the boat. Most of the air flows are on the sails some rise and goes over the top. So there is a zone in front of the boat where some air is rising. The zone behind where that air is falling back to the surface. You can think of this as a dome of air.

Bad air zone around the boat

Typical Upwind Trouble Spots

Now let’s look at the most typical upwind situations for clear air. Of course, the biggest one is the starting line. There are several trouble spots on the starting line. The worst one is being in the second or third row where the blanket and backwind zone. If you do not find an escape route to clear air you will continuously lose ground to the boats ahead.

Clear Air- Start

Another trouble spot is being part of a pack of boats in light air anywhere on the course that dome of rising air and falling air we talked about in bad air zones around a sailboat section. This happens on the starting line, sailing up the windward leg or downwind boats, and also at the windward mark. If you picture a dome surrounding a pack of boats you can understand why the boats in the middle of the pack even those toward the front see less wind than the boats on the ends of the pack. This is why a start near either end of the line in light air can get you away from the pack quicker and allow you to sail freely toward the new wind.

Typical Upwind Trouble Spots Pack

Some more trouble spots…

In this case, the wind is shifted to the left before the start. Have you ever been in this situation? If everybody is up on the line. Does every boat have clear air? If not which boat does have clear air? When wind shifts left all the boats are headed? Every boat is in the backwind zone. The only one boat on the left side is free from the backwind zone of other boats.

Typical Upwind Trouble Spots-Left shift

You have made it off the starting line. If you want to be able to follow your strategy. You have to able to hold a lane in the direction you want to go. In this situation, all the boats would like to continue on the port. Who is in the best shape to be able to do that? A and B have good wide lanes. C has clear air now, but just barely. If C does not sail all quite as high as A or if a small right shift occurs. C will quickly lose clear air, and it will have to decide whether not to tack. D is probably in A’s wind shadow or blanket zone and even if she is not.

Holding a Lane

Windward mark

Boats are all coming together so the potential for bad air is huge. Finding the cleanest air around mark can lead to big gains. Every wind mark rounding is different, and we cannot cover all the situations. Which boat is likely to gain the most in below rounding?

Windward mark

If you think about clear air A and C are the only boats sailing in clear air.
B, D, and E are in the backwind own of the boats ahead. E and D are ahead of C but C should be able to gain on them since C should be able to sail faster and point higher.

Clear Air – Start

Let’s talk about ways to get or keep clear air in some of the situations which we just talked about.

Clear Air- Start

What are the green boat’s options here and which is the best? A lot of books will tell you the tacking to port is the best option. Here are two reasons. First, remember that there is a port tack lift from the back wind zone of the boats on starboard with that lift green boat would not have to sail very far on the port to get to clear air. If going left is a priority it still might be better to tack to port first and find a lane and than tack back. But if that’s not workable you will have to try to hang with a group and stay on starboard. Do not be afraid to foot off if needed to do this.

Realize that everyone is still close to the leaders at this point at the start. So if you act quickly you won’t lose too much but you can lose a lot of ground quickly if you wait.

Keeping Clear Air – Windward Leg

Now let’s talk about the windward leg. Do you ever find yourself tacking? Realize you have to tack again too due to the lack of clear air.

The better approach is to make sure you will have a clear lane you can hold before you tack. This is usually easy in small fleets but it gets harder and more important in bigger fleets. Here is a simple example. If yellow wants to go right where should she tack? The answer is fairly obvious in this example. The yellow boat should be able to tack through blue and maintain her lane above Red. The yellow gets a small lift crossing through Orange and Red’s back wind zones. It would not be wise to tack behind Orange and Red.

Keeping Clear Air-Windward Leg

Here is another very common windward leg situation. B wants to stay on starboard and sees a coming on the port. What should B do? If B does not say anything A may decide to tack to avoid B even if A wants to keep going right. This would put B in bad air. B should encourage A to keep going. Too often we see the starboard boat just hailing starboard without considering the consequences.

Keeping Clear Air-Windward Leg2

Here is another situation showing the importance of positioning. It may be hard to plan ahead for this but when it happens it is not hard. If Red and Blue want to keep going on starboard who is more likely to keep clear air? This is pretty simple Red is safer, Blue is acting as a blocker forcing Green to either tack or duck. If Green tacked blue will be affected and Red will not.

Keeping Clear Air-Windward Leg3

Every windward mark rounding in a big fleet has different clear air challenges. Here are two situations. Would you advise Green to take the same approach in both situations? With all the boats already around the mark. In the top picture, Green may sail into very disturbing air if she keeps going on the port. It may be better for her tack earlier in situation one. She will be in disturbed air on the starboard lay line. But perhaps less so than the side of wedge of boats near the mark. In situation two as we saw before Green might gain more by staying on port longer and sailing in clear air assuming she can find a hole to tack into.

Keeping Clear Air-Windward Leg4

Some Reasons to Keep Going in Bad Air

Of clear air is not your only priority. Let’s look at some reasons you may want to keep going in bad air. Why might yellow choose to keep going in this pack? If you are going the right way say to the next puff or shift. It may be best to just keep going finding a puff or shift is usually more important. This is especially true if your air is not too bad maybe on a windy day or because you are just not losing that much. Perhaps the situation won’t last long and you can live in bad air for a short time while you head in the right direction.
With your head out of the boat, you can look ahead and consider your options.

Some reasons to keep in bad air


Let’s summarize the topic. We know that upwind boats generate three bad air zones.
The blanket zone is a direct shadow to lured and behind the boat.
Backwind zone is to windward and behind and it causes a header for boats on the same tack.

Finally, there is rising and falling air that creates a dome of weaker air around the boat.
Next, we should plan for typical trouble situations on the starting line if you are in the second-row tack away. If there is a left shift tack away. In any packs of boats anywhere on the course play the edges since there is less wind in the middle.

When you are sailing upwind get a lane wide enough to hold.

When approaching the windward mark approach on the port if possible.

Finally, when you do up and end up in bad air consider your overall strategy when choosing options. Tack away, Foot, Pinch, or Stay Put.


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