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Old 09-25-2003
Zack Leonard Zack Leonard is offline
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Basic Downwind PerformanceóPart One


Don't let anyone tell you otherwise, downwind legs offer the opportunity for boats to make substantial gains.

When I was a kid crewing for my dad in his old wooden Thistle, the downwind legs were a time for rest and relaxation. I remember his usual order: "Get me a beer, Zachary!" I would scurry forward to the starboard spinnaker turtle where I tunneled through the flotsam and jetsam for the small cooler that held four beers for my dad and two cokes for my mother and me. My mom chose to keep her wits about her during these races because the trip to the cooler was usually followed by a relaxed atmosphere on the part of the helmsman that occasionally led to a race-ending capsize.

As boats have become lighter and easier to surf or plane, downwind sailing has changed. Gone are the days of indulging in picnic lunches while steering the compass course to the leeward mark.

Aggressive downwind tactics and strategy are crucial to success in modern sailboat racing. So put away the Grey Poupon and open your mind to some new concepts that can help you put some major distance on the fleet.

 
Downwind, the boat behind has the advantage of being able to attack with its windshadow.
 
Thinking Ahead    A poor start, choosing the wrong side on the first beat, or sailing out of phase with the windshifts upwind are all mistakes that can leave fast sailors back in the pack at the first mark. But the best sailors know that downwind legs offer a great chance to get back into the race. Upwind, the leaders can beat back the boats behind them by tacking on their wind and forcing them to sail in dirty air or do extra tacks to clear their air. Downwind, the boat behind has the advantage. By blanketing the boats in front, the trailing boat can force them to jibe to clear their air, or give up distance away from the rhumb line as they head up to get clear air.

On a run, boats can choose to sail straight to the mark along the rhumb line, or to jibe back and forth taking advantage of windshifts and puffs to keep the boat moving fast. That's why downwind sailing is often referred to as open-field sailing. Your options are wide open and identifying several key variables can help you to make some big gains.

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A big group of boats approaching the windward mark on a layline creates a zone of broken-up airóno-manís land. In the case above, boat A shouldn't jibe until he's clear of the bad air.
 
Itís important to remember that the run doesn't begin when you round the windward mark, it begins as you approach the mark. Good downwind racers begin to talk about the run long before they get to the windward mark. Try to take note of all the pertinent factors including the current direction and strength, the geographic wind advantages from side to side, which tack is lifted approaching the mark, and try to get a visual on the leeward mark even before rounding the windward mark. That seems a lot to ask, but all of it will become second nature after a while. Remember, itís easy to lose valuable distance and give away positions to competitors by rounding the windward mark and sailing all over the chart while trying to spot the next mark.

If you go around the windward mark as part of a large group of boats, executing your game plan can be a challenge. Boats often bunch up while they look for the mark and struggle with sail controls and spinnakers. Your primary goals upon exiting the windward mark are to sail the boat full speed, in clear air, and pointing in the direction you've decided you want to go. Immediately after you round the mark, you need to be mindful of boats that are still sailing upwind, particularly if youíre racing in a large fleet. If the left side was favored on the beat and the whole fleet was sailing near the port-tack layline, you might be able to escape the cluster by jibing immediately to get clear air. However, itís more likely that the fleet will be stacked up on the starboard layline, so a jibe, even to clear your air from downwind boats behind you, can land you in no-manís land. This is the area just to leeward of the mark where the air is entirely broken up from the upwind boats still approaching the windward mark.

Clear Air = Better Boat Speed    How can you determine if your air is clear downwind? The best way is to use telltales on your shrouds. Simply draw an imaginary line parallel to the telltale pointing back upwind behind you. If that line is pointing at another boat that is anywhere close by, then you are sailing in that boatís windshadow. What strategies can you use to clear your air? First, you can head up, which will clear your air out in front of the pursuing windshadow, but this usually means youíll be sailing extra distance to get to the mark. Second, you can jibe. Jibing will clear your air quickly and can sometimes take you back closer to the rhumb line.

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Downwind, you have two options to clear your airóhead up or jibe. In the example on the left, boat A should head up. In the example on the right, boat A should jibe.
 
Given the choice, you should choose the method of clearing your air that allows you to sail the favored tack or gets you closer to the rhumb line. If staying on the favored tack means heading far above rhumb line to clear your air, then consider a quick jibe to the unfavored tack, and then a jibe back to the favored tack so you'll have a clear lane. Of course, if one side of the run has a lot more wind than the other, you should always clear your air toward the side with the increased velocity. (That brings up an important pointóthough youíre sailing downwind, at least one person on the boat should focus his or her attention upwind, where the wind is coming from. With some practice, almost anyone can learn to read the wind on the water to know where the best breeze is. Iíll discuss this further in Part Two of this series.)

Every boat has an optimum angle (upwind and down) for each wind condition. This angle is usually referred to as the best velocity made good (VMG). The best VMG course is the one that will get you to the leeward mark fastest, including jibes, in the absence of any windshifts, wave activity, or current. For most keelboats, you can obtain VMG charts or velocity prediction programs that will show you what angle is fastest for your boat in a given breeze. If you race dinghies and planing boats, you must develop a feel for the speed gains you can attain by reaching up and going faster. For some very fast boats, especially catamarans, extreme gains can come from sailing very high and fast, nearly doubling your boat speed. These boats tack downwind much like we tack upwind, maintaining optimum boat speed while zigzagging down the run. However, for the purposes of this article, letís assume you are racing a more conventional boat that will gain some speed by sailing a little above dead downwind, but not a quantum leap.

Headers and Lifts    The goal of the run is to sail in clear air, in the most wind, pointing as close to the rhumb line as possible while sailing your boat at its optimum speed and angle for the wind velocity and wave conditions. If your boat sails fastest in 12 knots of wind at eight degrees above dead downwind, then you want to sail eight degrees above dead downwind on the jibe that diverges least from the rhumb line to the mark. This means you need to sail on the headed tack! A header is defined as a shift that brings the wind forward on your boat. Upwind, we know that a header causes us bear off, pointing farther from the direct course to the windward mark. Downwind, a header has the same effect, causing us to bear off. However, if youíre sailing downwind and you get headed, you can simply sail the same course while adjusting your sails for the new, tighter angle and therefore sail faster. Upwind, we sail on lifts and tack on headers to point as close as possible to the windward mark. Downwind, we sail on headers and jibe on lifts to sail tighter and faster down the rhumb line.

 
Before you round the windward mark is the time to consider strategy for the leeward leg.
 

Sometimes an upwind leg isnít square and you find youíll sail much more of one tack than the other to get to the windward mark (in this case the wind is right or left of center on the racecourse). Unless the race committee intervenes and moves the next mark, this situation means that downwind, one tack will be a much tighter angle than the other, and that jibe will take you down the rhumb line at a tight, fast angle. If this is the case, sail the header and reach to the mark while leaving your rivals in the dust.

Knowing how to clear your air and determine which tack is headed at the windward mark will pay big dividends in your downwind sailing. The next time youíre out racing, or even just sailing downwind among other boats, give these basic concepts a try. 

Managing the Current

Unless there is a difference in depth across the course or one part is closer to the shoreline than another, it's rare that one side of a run will have a current advantage. But, if the current is running sideways across the course, there are gains to be made. If you round the windward mark to port and the current is pushing you sideways, say right to left, you will slowly be moving off the rhumb line even while youíre pointing your bow right at the mark. As you get farther down the leg, you may have to jibe and sail a very tight reach to get to the mark, or just continually head up and sail higher and tighter as you move down the leg and get flushed to the side. This is called the great circle route. It means that you are slowly being swept off the rhumb line by the current.

The smart money is to take the jibe that allows you to point to the up-current side of the mark. As you sail along, watch the land behind the mark. If it is slowly moving one way or another and your boat is pointing right at the mark, then you are being swept by the current. Sail the course that allows you to hold land on the mark, meaning that the same spot of land is staying right behind the mark. By sailing the up-current jibe and holding land on the mark you will actually be able to sail the true rhumb line on the tighter angle, which is almost always a winner.



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In Part Two of this series, Zack Leonard discusses how to manage oscillating winds, puffs, and velocity changes, as well as how to set up for a great leeward-mark rounding.