Editor's Note: Since this story was first published, we acknowledge the author's suggestions run contrary to Rule 42.3 and its limitations. Specific classes mentioned, however, including the Melges 20, do modify class rules to allow unlimited pumping. For more on Rule 42.3, Propulsion

A few years ago, I was working with two Melges 20 teams in preparation for an upcoming world championship. Both had world-class sailors aboard and performed quite well, but when it came to downwind pumping technique, there were dramatic differences. Generally speaking, one team worked mostly with large, powerful pumps while the other focused on smaller, short-stroke movements. Sometimes one technique worked better; other times it didn’t. So, we set out to quantify the difference in performance to get a better sense for which technique was most effective in various conditions.

Our boats were instrumented, and we had data feeds coming off each boat, so we could plot VMG. I also had a program called Dartfish, which among other things, could plot movement at the end of the boom, making it clear what type of pumping was being used. Tracking the end of the boom through the various pumping methods reveals just how dynamic these movements are. Impulse pumps produce pretty straight tracks, with the boom moving pretty horizontally. Rowing pumps, and sometimes reverse pumping, created tracks that were quite elliptical. The ellipses could even be diagonal, indicating the pumps were pulling down as well as in. We started plotting those data numbers on a graph and compared that to acceleration over certain periods, and we started to see a pattern that suggested where each type of pump worked best.

Rowing Stroke

This is what usually first comes to mind in any discussion of pumping. You lean forward, using your back, leg muscles and upper body, and aggressively pull on the sheet, much like a rowing stroke. It imparts a huge amount of energy into the boat, and it’s what you see when a bird starts to take off. It’s not making little strokes; it’s doing the big, long, quick strokes to produce maximum lift. This type of stroke is great in lightweight keelboats and dinghies, when you’re in marginal conditions, right on the edge of catching waves, and you need that big impulse of energy to get your boat accelerating onto the wave and being able to start gliding in surfing mode using the downhill side of it. It’s a relatively quick pump, but it’s got a huge amount of force.

We discovered that rowing the boat onto a wave with this stroke was a pretty good technique in marginal planing and surfing conditions, until you got “on the step,” meaning you’ve started planing down the wave, and the apparent wind has increased and shifted forward. The problem with a rowing pump, once on the step, may have to do with the fact that your steering angle is now much narrower, so when you do the big eases and trims, you’re stalling the sail at either end of the pumping range — the sail is no longer trimmed perfectly. The rowing pump also has the same effect as moving the crew weight. That roll, usually from zero to 7 degrees, can kill flow on the foils. Once on the step, it’s all about efficiency; you lose if you try to put too much energy into it.

With heavier-­displacement boats, the returns on the rowing stroke diminish rather quickly as the boat gets bigger and heavier. With a pro crew and linked winches, you can probably make it work, but otherwise, it will only stall the sails.

Impulse Pump

Now you’re surfing down the wave, but sooner or later, you start decelerating. It’s like the wave is accelerating compared to your speed, but in reality, you’re just slowing down. This is the time to give a short, snappy pump — one that gives just enough impulse to flick the mainsail and asymmetric spinnaker leech, imparting enough energy to reaccelerate and continue riding down the wave. Returning to my bird analogy, once it’s flying, it just needs small, tip-of-the-wing ­movements to keep it going. When we’re using the impulse pump, we already have a lot of kinetic energy going because we’re planing; all we’re trying to do is match that speed.

If the boat gets really loaded up, the short, quick impulse pumps will keep the boat going. The boat is quite delicate in the planing mode, so resist the urge to give it a big pump. Once the boat is planing, stick with impulse pumping. This type of pump will work on heavier boats, even with symmetric spinnakers, once on a plane. For the spinnaker, just make sure the guy and sheet are pumped simultaneously.

Reverse Pump

We always think of pumping as pulling, but the most important technique is actually the reverse pump. The idea is to let the sheet go out just a little bit — generally several inches or so — and then quickly catch it, or stop it. That reflexes the entire sail open and then reflexes it closed again. It’s the recharge pump that gets the flow back on the sail, so both the rowing pump and impulse pumping are closely connected to the reverse pump. Watch some really good singlehanded, dinghy or keelboat sailors, and you’ll see them flip their hands open; the sheet goes out, and then they stop it hard. They don’t pump; they just stop the motion. The whole sail opens up, regaining flow, and then closes again.

Suppose you have a gust coming on. You’re already planing, but you’re not going to deal with the gust by easing the sail out so that it’s ragging. So, you do a quick reverse pump as it hits, briefly releasing the leech, which gets rid of a little helm. You can usually feel that change. Then the leech snaps back in naturally. Or, it may be that you’re just trying to get over a wave. The boat gets loaded up for a few seconds, and that’s when you give it a little reverse pump. It’s an excellent technique for when there isn’t enough weight in the ­mainsheet to do a traditional pump.

Modern boats sail downwind through as much as 80 degrees. They’re apparent-wind machines, and we can use the three pumping modes to sail quite different courses.

The reverse pump is strong in all conditions. We use it a lot on asymmetric-spinnaker boats now because, with the ­windward-leeward courses, it’s all about VMG — how low we can go, not how fast we can go. On a TP52, even in planing and surfing conditions, the asymmetric trimmers will sometimes give the sails a little ease and then a hard stop. The sail is trimmed correctly, and then they just go out from there. It might produce a little curl. The same with the mainsail trimmers, and when it’s done together, the boat reloads, as it allows you to pump again. The reverse pump works well on heavier, symmetric-spinnaker boats too.

Unless we’re in very strong conditions, it’s difficult to jump to the next set of waves, so no longer do we sail straight courses. Modern boats sail downwind through as much as 80 degrees. They’re apparent-wind machines, and we can use the three pumping modes to sail quite different courses. When we catch a wave, we can go really low, using impulse pumps and reverse pumps to keep it going. Then, at the bottom of turn, crew weight moves to leeward, even on keelboats, to help the boat turn back up. We reload the upturn as the apparent wind moves aft, and put more force in the sails, then, with a big rowing pump, off we go again.

Combine the above with steering techniques largely derived from the 49er and 470, and downwind trim becomes dynamic to the point where upwind sailing is no longer the most physical part of the race — that’s now the downwind legs. Even bigger, asymmetric keelboats are beginning to be sailed like dinghies, shifting weight around to help steer in addition to constantly shifting from one pumping mode to another, working to promote and maintain a plane. It’s fast, so get pumping.