Velocity Headers
By Allen Edwards
Introduction
I don't think there is a subject so misunderstood than velocity headers. They can take an entire fleet and get them to all stop dead in the water where a boat that recognizes what it going on can sail right through them. I know because I have done it. We went from last to first to finish in a fleet where we were neither the biggest, fastest, or lightest boat and yet there they all were stopped as we went right by, sails luffing away. Here is a video of that race.By a minute into this video our main is luffing but a bit later we have slowed down enough to be sailing again. Meanwhile, the other boats are trying to build speed back up from having stopped their boats. We crossed the line first in our fleet.
What is a velocity header?
A Velocity Header is a shift in the apparent wind forward due to a change in the true wind velocity without any change in the true wind direction. The correct response to a velocity header is to sail in the direction you want to go until your boat slows down to the target speed for the lighter winds.What Target Speeds


The Pre Shift condition
12 kt wind, 6.1kt boat speed, 45 degrees to wind.
For this example I am going to assume you are sailing in 12 knots of wind and you sail into an area where the wind is 4 knots. First lets look at the 12 knot condition and see what the boat is doing. Looking at the table above we see we are sailing 6.1 knots and we are likely sailing at 45 degrees to the true wind, a typical heading upwind. We can use the wind angle calculator HERE to see that the apparent wind angle is 30 degrees. At 30 degrees of apparent wind, the windex is lined up perfectly and everyone is happy.The Velocity Shift Hits
Header! Fall off! No - TACK! Oops, Stopped.


The Correct Response
4 knots wind, 1.9 kt boat speed, 47 degrees to wind.
The goal is to be sailing at 45 (plus a couple in the light wind) degrees to the true wind at our target speed of 1.9 knots. Not very fast compared to the 6.1 knots we are going but it is our target speed. What should we do? The answer is that we want to slow the boat down until we are at our target speed at which point we will be sailing again. But we want to take as long as possible to slow the boat down. We want to coast and we want to do it in the direction we want to be going. Typically the direction we want to go would mean that we want to head up and not fall off. But changing course will slow us down quickly and we would then need to fall off once we got down to our target. Plus, we might have miss judged our target and slow down too much. So the best thing is to probably not head up but certainly not fall off to try and fill the sail. The main has centered itself and is luffing. But what about the jib? It is back winded -- release it! That's right, just let it go so it isn't slowing you down. When your windex gets back to 30 degrees and your boat speed has bled off, trim.Easier Said Than Done
Practice Makes Perfect.
There are many obstacles to pulling this off. First is that you have to be correct in your evaluation that this is a velocity header and not a true header. Next you probably have crew yelling at you that you are luffing and need to fall off. Best to teach them about velocity headers ahead of time. The best way to learn about velocity headers is to get in one, fall off, tack, stop the boat, and watch some other boat sail by you. That is how I learned about them.What About Velocity lifts?
A Much Smaller Gain
Velocity lifts are situations when you are in light winds and you enter a strong wind that has the same direction as the light wind. Most people will head up because when the stronger wind hits, you will feel a lift. In our example, you will be 41 degrees apparent. But you are sailing in the right direction, just too slow. You want to be going 6.1 knots, your target speed, and you are going 1.9 knots (but not for long no matter what you do). The correct response is to let the sails out, hold your course, and get to 6.1 knots as quickly as possible, then trim. Again, you will have crew yelling to head up in the puff but if you are correct and it is not a puff, hold your course and accelerate instead of heading up. If it is a puff, well maybe you called it wrong. No matter what you do in a velocity lift, you will be going 6.1 knots soon enough and you won't stop the boat. They are much less dangerous than velocity headers, which is why this article is focuses on the former and not the latter.A Picture of Papoose

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