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Downwind
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Автор: Денис   
26.11.2009 16:36
Индекс материала
Downwind options
Proper course
Downwind penalty
Bear Away Set
Tack Set
Gybe-Set
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DOWNWIND OPTIONS

The tactical options for a team downwind are dependent upon the relative positions of the boats, the strength of the wind, the variability of the wind (in speed and direction) and the performance characteristics of the boats.

The leading boat has the option of choosing which side of the course to sail, at least initially, and can round the top mark with a 'bear-away' set (taking the right side of the course), or a 'gybe-set' (taking the left side).

The trailing crew could then split sides, by doing the opposite. This gains the trailing team some lateral separation which it can leverage into a gain if it finds either favourable pressure, or a beneficial wind shift.

In lighter wind, the boats will set asymmetric spinnakers, which force the teams to sail higher angles (closer to the wind) and make it more difficult for a trailing boat to 'blanket' the leader, with its windshadow. At those higher angles, the apparent wind angle is so far forward, a team needs to get forward of bow to bow to affect the wind of the other boat.

In stronger winds, with symmetrical spinnakers, the boats sail more directly towards the leeward mark, and the trailing boat will be more likely to throw its windshadow on the leader if it is within a couple of boatlengths.

In the following example, the trailing boat Blue, has followed Yellow around the mark. By not doing a 'gybe-set', Yellow has decided the favourable wind is on the right side of the course.

At position '1', Blue can gybe first, taking the left side of the course, wait and gybe at the same time as Yellow, in hope of getting bow forward enough to affect the wind Yellow gets, or switch sides by continuing on if Yellow gybes.

In this example, at position '2' Blue gybes first, and Yellow immediately follows to prevent Blue from gaining any significant separation on the left side of the race course.

These 'simultaneous gybes' are an excellent opportunity for superior crew work to gain your team a few metres.

At position '3' Blue gybes a second time, and Yellow again responds in kind immediately, protecting the right side of the race course.

When Blue gybes in position '4' Yellow follows and is in a strong position. Blue would need to make a massive gain to be able to gybe and cross in front. From this position, Yellow can sail Blue down to the port gybe layline, before turning for the mark, and leading Blue around the leeward mark.

Crew work and equipment reliability are critical on the downwind leg. Gybing in light wind with the asymmetrical spinnaker is risky, as there is always a chance of the sail getting wrapped on the forestay or torn on a spreader. In stronger winds, the sail itself is at risk of tearing, and a small defect can quickly result in a tattered sail. The spinnaker pole too is under tremendous strain, and any small mistake can manifest itself in a broken pole very easily. Although it often appears to be easier sailing, with the boat relatively flat compared to the upwind legs, sailing an America's Cup Class boat downwind is no time to relax.

While a trailing boat can often make a gain on the downwind leg, it is much more difficult to convert that into a clear lead change. A team that makes a pass on the run has done a magnificent job.