The short version
- Don't just point at the mark
- Sailing at an angle is longer, but often faster to the mark. 20° off dead downwind adds only 6% to the distance.
- Gybe on the lifts
- Downwind, a header lets you bear away toward the mark, so stay on that gybe. A lift forces you to head up away from it, so gybe.
- Follow the pressure
- Puffs come from behind. Look over your shoulder, gybe to stay in them, and bear away in a puff, head up in a lull.
- Keep your air clear
- Boats behind you take your wind. Don't sail straight down the line between them and the mark.
Why the straight line isn't the fastest
On a run, the leeward mark is usually straight downwind, and the obvious course is to point at it. The trouble is that most boats are slow sailing dead downwind. The sails are only being pushed, not drawn along by air flowing across them, and the boat's own speed takes away from the wind it feels. Head up 20 or 30° and the wind moves round toward the side, flows across the sails, and the boat speeds up, often by a lot.
The question is whether that extra speed is worth the extra distance. The measure is VMG (velocity made good): how fast you're actually getting downwind, whatever direction the bow points. It's the number that decides who reaches the mark first.
The extra distance grows slowly at first, then quickly:
| Off dead downwind | Wind angle | Extra distance |
|---|---|---|
| 10° | 170° | 1.5% |
| 20° | 160° | 6% |
| 30° | 150° | 15% |
| 40° | 140° | 31% |
Extra distance = 1 ÷ cos(angle off) − 1. To pay, you must be at least this much faster at that angle than sailing dead downwind.
Finding your downwind angle
The best angle depends on the boat and the breeze:
- Asymmetric spinnakers and fast boats (skiffs, sportboats, catamarans) gain so much speed by heading up that they almost always sail angles, and gybe through 70–90°.
- Symmetric spinnakers and slower boats can sail much deeper. In a breeze many sail close to dead downwind, because they're already near their top speed and heading up adds distance without much speed.
- In light air, head up more. Extra speed makes extra wind across the sails, and that's what the boat is short of. In a breeze, sail deeper, because the boat is already fast.
Your class's polar (a chart of boat speed at each wind angle and wind speed) gives a starting angle. On the water, the test is simple. If you bear away and the speed drops a lot, you've gone too deep. If you head up and the speed barely changes, you're sailing too high for nothing. The most common mistake is sailing too deep because it feels calm and comfortable, while the boat quietly slows down.
Wind shifts downwind: gybe on the lifts
Upwind, you tack on the headers. Downwind, the logic turns around, and it's worth getting straight once.
Hold the angle to the wind that you've found is fastest, and let the shifts move your heading. A header is a shift that comes from further ahead, and a lift is one that comes from further behind. Upwind, a lift lets you point closer to the mark. Downwind it's the other way round:
- Downwind, a header lets you bear away, so you point closer to the leeward mark. That's good. Stay on that gybe.
- Downwind, a lift makes you head up to keep your angle, which takes you away from the mark. Gybe. The other gybe is now the headed one, pointing closer to the mark.
A worked example. The wind is from 000° (north) and the leeward mark is due south. At your best angle you head 210° on starboard gybe and 150° on port, each 30° off the mark. Now the wind veers (swings clockwise) to 010°. On starboard, to hold your angle you must head up to 220°, now 40° off the mark: a lift. On port you can bear away to 160°, only 20° off: a header. Gybe onto port.
Two quick checks keep it straight:
- Whichever gybe points closer to the mark at your best angle is the right one. Everything above comes back to that.
- The tack that was lifted on the beat is the wrong gybe on the run. If port was paying upwind because the wind had backed (swung anticlockwise), starboard will be pointing closer to the leeward mark. Gybe early.
Spotting shifts downwind is harder than upwind. The wind across the deck is lighter, the boat swings around more in waves, and you're watching your speed, not your compass. Compare your heading at your best angle with the one you had on the same gybe a few minutes ago, the same way you would upwind (see playing the shifts). On starboard gybe a lower compass number means headed, and on port a higher number means headed.
Pressure: sail where the wind is
Downwind, more wind usually matters more than a shift. Puffs travel down the course in the same direction you're going, so a boat that finds one can ride it for a long way, and the fleet often stretches out on a run for that reason.
- Look behind you. The darker water is coming toward you. Gybe or adjust your angle so it reaches you sooner and stays with you longer.
- Bear away in a puff, head up in a lull. When the puff hits, the boat speeds up and you can turn the extra speed into depth (sailing closer to straight downwind). When it fades, head up to keep the boat moving. It's the same rule as finding your angle, applied second by second.
- Don't sail out of a puff to reach a shift. A few degrees of shift is worth less than staying in stronger wind.
Clear air and the boats around you
Downwind, the boats behind you are upwind of you, and their sails block your wind. A boat two or three lengths behind and directly upwind can slow you badly. Keep out of the line between a boat behind and you. Head up or gybe to get clear air, rather than sailing in their shadow. The same works the other way: when you're behind, point your wind shadow at the boat ahead.
Plan the end of the run early. Which side of the leeward mark or gate you want to round (see leeward gates) decides which gybe you want to arrive on, and the boats with room at the mark are the ones who got there inside (see how to round a mark).
Doing it with Sail Tactician
The target angle is only as good as your wind. If the wind you set is off by 10°, so is every downwind number. Set it on the water, head to wind, before the start.
Questions
Is it faster to sail dead downwind or to gybe downwind?
It depends on the boat and the breeze. If heading up 20–30° makes you more than 6–15% faster, sailing angles and gybing wins. Fast boats and asymmetric spinnakers almost always gain. Symmetric boats in a breeze often sail close to straight downwind.
Should you gybe on a lift or a header downwind?
Gybe on a lift. Downwind, a lift makes you head up away from the mark to keep your angle, while the other gybe is headed and can point closer to the mark.
What is VMG downwind?
Velocity made good: how fast you are getting directly downwind, or along the leg toward the mark, whatever direction the bow points. Sailing faster at a wider angle can give a higher VMG than sailing slowly straight at the mark.
Why do the boats behind catch up on a run?
They often bring the new pressure down the course first, and their sails take the wind of the boats in front. Watch behind you for puffs, and keep out of the wind shadow of the boats behind.
Sources
The extra-distance figures are trigonometry: a course at an angle θ to the direct line is 1 ÷ cos θ times as long. Shift and pressure tactics are standard club-racing practice. The downwind VMG drill is adapted from Sail Tactician's in-app training guide. Sail Tactician behaviour from the in-app User Guide, version 3.2.
What changed
- First published.
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