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When to tack – can racers and cruisers learn from comparing notes?

Olympic coach Mark Rushall looks at what may determine our decision making, from sea state to pressure patches to tide

 

Club racers determined to finish further up the fleet, and day cruisers keen to get to their destination for the celebratory sundowner often face similar dilemmas: could they each learn by comparing notes?

In this feature I’ll use my own experience of racing our RS200 at the local club, and cruising our 60 year old classic in the Solent and Channel to highlight some of the questions that both club racers and passage makers might try to answer, to come up with a solution for “getting there quicker”.

In a recent article in Sailing Today with Yachts & Yachting, Helena Lucas talked about different sorts of wind shifts and suggested the best strategies for each.

  • If the wind is shifting regularly around a mean direction, tack if the shift makes you sail below your mean heading. That way you will sail the shortest distance upwind. Upwind, you are tacking on the headers. Downwind, gybe on the lifts.
  • A “wind bend” could be caused by the wind deflecting around an obstruction, for example a headland. Think of it as a running track, and sail toward the inside of the bend to sail the shortest distance upwind or downwind.
  • If over the period of the leg you are sailing, the wind is moving persistently in one direction, tack towards the new wind direction to sail the shortest course upwind.

There is plenty more to throw into the strategic mix, for example tide, sea state, varying and changing wind strengths, gusts and puffs. Most books and articles are written with a perfectly square beat or run in mind: club racers and passage makers have to take into account that a beat or run may not be square, and you’d have to have a very good reason not to simple take the tack or gybe that takes you closest to the destination.

The key to “getting there quickly” is to narrow down the focus to a couple of clear priorities: as we’ll see later its often better to execute a less than optimal strategy well, than to make decisions at random or attempt to take advantage of every single variable and compromise them all.

 

Know your boat

I once gave a talk to a group of “ship racers” in Holland: their most important strategic factor was the depth of the water on their racecourse. A flat bottomed “ship” with just a few cm clearance below the hull is significantly slower than one sailing in a metre of water!

Knowing the characteristics of your boat is the first part of narrowing down your strategic priorities on any given day. I’ll take my two examples and see how their characteristics might affect my decision making: have a think about the characteristics of your boat and see where they fit in.

The RS200

The RS200 is light, quick to accelerate, and highly manoeuvrable.

Upwind: When we are underpowered (not fully hiking), a small increase in wind speed (“pressure”) makes a huge difference to boat speed. More pressure means we point higher and go faster. The boat’s quick acceleration means in light winds we’d be seeking out even a short-term patch of pressure. In light or medium winds, a good roll tack will probably give a VMG (speed made good towards the wind) gain, so even if the shifts are short lived, it is always worth tacking on a big one.

Unlike a trapeze dinghy or a windsurfer, we never plane upwind. Once we are both hiking the VMG gains in more pressure are low. There will probably be more important strategic factors for us in more than 8k of windspeed.

The “sweet spot” – the beating angle that gives the best possible VMG in each condition – is pretty narrow. (A “narrow groove”).  Pinching or sailing free is inefficient, and overstanding a mark is a really painful waste of time.

Downwind: The fastest point of sail without the spinnaker in most wind strengths is beam reaching. Broad reaching with no spinnaker is really slow, so it may be worth doing a marginal spinnaker leg in two parts, one beam reaching and one at the optimal spinnaker reaching angle some 30 degrees lower.

The boat’s downwind characteristics are completely different below and above a magic wind threshold of around 12 knots. Below 12 knots, we’re trying to sail as low as possible without the spinnaker collapsing. So long as the kite is filling, there is a fairly wide angle giving a similar downwind VMG, so we are very happy to sail high if we can see extra pressure coming down from to windward, and then soak low once we are in it.

A small increase in pressure lets us sail both deeper and faster so in changing conditions that is going to be the priority. If the pressure is even, the wide downwind angles and easy manoeuvrability mean that it will always be worth gybing on the significant shifts, this time aiming to always be on the headed tack.

Above 12 knots, the best VMG is made by keeping the boat planing. There is now a much narrower groove so unless we gybe, we have few choices: pressure is still the priority: we gybe toward more pressure when we can and try to stay on the headed tack downwind when we can’t.

Both upwind and downwind, our sails are small compared with the other boats in our fleet. So, we always need to be aware of the patterns of boats and looking out for clear lanes may take priority over other strategic factors.

Honeybee design Ragdoll competing Panerai British Classic Week 2016
Ph: Guido Cantini / Panerai / SeaSee.com

Honeybee: Ragdoll is a traditional long keel boat, 28ft long and weighing nearly 5 tons. She is slow to accelerate and very susceptible to stopping in the Solent chop.

Upwind: When underpowered, a knot of extra pressure makes an enormous difference to VMG. But a short-lived gust has little effect: we are more interested in looking for long term areas of more pressure, for example on one side or the other of the Solent.

Depending on the wave state, it can take up to 2 minutes to get her up to speed after a tack, so shifts of short period are simply distractions. Ragdoll has a very wide upwind groove so we might put the bow down in a lift to get out of the tide or into more pressure, or sail with the inside tell-tales lifting (“high mode”) to squeeze up to where we want to be in a header. Looking for flatter water is always high on our priority list, even if it means sacrificing some favourable tide when wind is against tide. Once fully powered up, there is little point looking for even more pressure: the boat does not go any higher or faster! We’d be weighing up the pros and cons of any longer period shifts or tidal advantage in that case.

Downwind: We have a nice selection of spinnakers, from the “whomper” to the “nighty”. Until we are up to hull speed with the whomper in around 8 knots of wind, finding more pressure makes the most difference. Once at hull speed, we don’t go much faster: we just roll more, or even have to peel to a smaller kite: that is very slow with just one halyard! With the kite up, our VMG changes hardly at all with angle and we can pretty much sail dead downwind or by the lee: there is not much point worrying about small windshifts!

So, we’ll be looking for other strategic factors: on the Solent that will probably be the tide.

For each boat we now have a mental checklist for what the priorities might be in each condition. For example, for the RS200, upwind in light winds the checklist might look like this:

  • Light winds upwind
  • Look for pressure first
  • Tack for shifts and pressure
  • Keep clear wind
  • Stay inside laylines

 

The 2015 Rolex Fastnet start

Know your venue

What do we know about the race or passage venue? Past experiences should never become dogma, but every venue has its repeating themes. Given the same conditions these could form a part of the strategy.

For example, at my home club, in a southerly, the shallower water is on the left-hand side of the beat, that’s where I’ll be heading if I’m after some tidal relief. In a north westerly, the cleaner wind at the top of the creek is on the left, if pressure is my priority that’s useful winning knowledge. A north easterly blows straight over the town and is often shifty and gusty with no real pattern: I have no way of knowing when and how big the next shift will be. If I treat as a regular oscillation I may never get to the windward mark!

In the Solent, the “Winning Tides” book gives great insight into where the tidal advantage may be, for both cruising sailors and racers. The sea breeze often tracks toward the west, giving a long phase persistent right shift for west bound travellers. And “when the wind’s in the North, go North” obviously means something to those who spend time on the Hill Head plateau!

As well as repeating themes particular to the venue, think about the specific leg ahead of you, whether rushing to anchorage or racing to a mark.

  • Is it that idealised perfect beat, where spending equal time on each tack will get you there?
  • Does the geography or cross tide skew the leg, so you’ll have to spend significantly more time on one tack than the other?
  • If there is tide involved and it is not consistent along the leg, how does this affect your track, and how does it affect your sailing wind on each part of the leg?
  • If it’s a reach, are there choices to make between sailing a straight course over the land, sailing the shortest distance through the water, or as with the RS200 downwind example above, sailing a much longer route at a higher overall speed?

 

Recognise the type of day

Even the simplest forecast, plus an eye to the sky can give you an indication of general trends, of shiftiness and gustiness, likely changes and visual indications that might forewarn those changes.

A sea breeze would suggest a relatively steady direction with small shifts, maybe a slow swing relevant to a long leg but not a smaller one, and fairly even pressure once the breeze is established. That might have you checking out the bigger permanent features, like wind bends or tidal gradient, rather than focussing on the relatively small shifts.

Individual rain clouds each bring their own associated pattern. In that case focus might be on the clouds, shaping the beat or run to take advantage of the large shifts and squalls as each one passes by (while avoiding the calm and the wet directly underneath!).

If the forecast suggests a permanent shift and also shows a change in the temperature and cloud cover, it is probably something to do with a front. The approaching line of cloud may signal the change and direct your strategy: a glance at a synoptic chart would help the diagnosis.

A large lull to gust range on the forecast suggests high instability: there will be plenty of opportunity for gains from the shifts. But if that shifty wind is forecast to arrive over or around a large hill, town or cliff, those shifts may be unpredictable and irregular as well.

 

Sorting the priorities

Hopefully, reminding yourself about your boat, your venue, the leg configuration, and the conditions of the day has narrowed down your priorities for the leg to one or two areas of focus. On most days, the process of thinking through these four areas is enough to clarify the focus.

Sometimes it is not: the gains possible from each variable are actually very close and it may be tough prioritising one over another: that’s what makes the strategy of sailing so fascinating. For example, in the table below I’ve used estimated performance figures for the dinghy and the cruiser in 8 knots of wind and compared the effect of pressure differences, windshifts, and a typical tidal gradient (different tide direction or speed in different parts of the leg).

In an ideal world you’d tack on the shifts, sail to the pressure, and take advantage of the tide differences. But strategy is not always that straightforward. If you had to make a choice, you might choose the effect that you have most confidence in predicting: the tide in the Solent, for example, is well documented. Or you might choose the one that you can actually see: if the water is flat, you can spot the darker areas where there is significantly more pressure.

However, and whichever you choose, my experience of “getting there quickly” is that the sailor who sails to a thought-out strategy will almost always be around the mark or into port before the one who “points and hopes”.

 

Gain from 2k wind speed difference Gain from 20-degree windshifts Gain from 0.25k tidal gradient
Keelboat upwind in 8k wind 9 minutes per hour 8 minutes per hour 7 minutes per hour
Dinghy upwind in 8 k wind 10 minutes per hour 7 minutes per hour 7 minutes per hour

 

This article first appeared in Sailing Today with Yachts & Yachting magazine, bringing you a monthly dose of sailing wisdom from Mark Rushall and our other expert writers. You can try a single issue purchase or subscription here

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