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.
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.
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 you’re 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, it’s 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-man’s 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 boat’s 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 you’ll 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.
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, let’s 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.
Sometimes an upwind leg isn’t square and you find you’ll 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 you’re out racing, or even just sailing downwind among other boats, give these basic concepts a try.
Managing the CurrentUnless 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 you’re 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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