It is tactical decision every skipper makes in any Rolex Sydney Hobart Yacht Race. The right choice and you're a hero. Get it wrong and it can cost you the race. And as the boats have changed over the years he equation has been shifting.
As the fleet turns south at the seaward mark off Sydney Heads do you take the rhumb line, the shortest distance between Sydney and Hobart, or at some point do youhead out to sea looking for extra wind and the current?
It is a feature of the NSW coast that a warm current runs south between 15 and 30 miles offshore It is like a giant moving footpath where even a becalmed yacht can cover two, three, sometimes four miles over the ground in an hour. There are also current patterns in Bass Straight.
Lindsay May, one of the wiliest tacticians in Australian yachting loves the current. He says he will go a long way off the rhumb line to find it. In 2006, at the helm of Love & War, he rode an unusually strong current to a famous victory. 'We have just had the most amazing race with current,' a jubilant May declared when he arrived in Hobart. 'On the first night we had four and a half knots.'
That was exceptional. Typically the current will be around two knots, yet for a boat like Love & War, sailing at six to seven knots to windward even an extra 2 knots represents a 33% boost in speed. There is a trade off, though, especially if the current running south is opposed by winds coming up from the south.
Off the southern New South Wales coast especially, the combination produces big, steep seas that can break boats and test crews to the limit. In 2006 both the New Zealand maxi Maximus and the round the world Volvo 70 ABN Amro lost their masts in the rough conditions. 'Last year a lot of faster boats stayed out of the current because they wanted to avoid the rough sea,' May recalls, 'but it wasn't as bad as we expected and it meant that every hour we got an extra two or three miles on them. I think that all up current boosted us by 150 miles that race.'
Rolex Sydney Hobart veteran and two-time overall winner Roger Hickman says he is obsessed by the current. 'All of the boats have thermal imagery, trying to find it,' he says. The current is warmer than the surrounding water. 'Our strategy is built around the assumption that there is current, it's a trend you always have to watch. We have the set and drift up on display all the time. Every ten minutes I check what the current is doing.'
'We used to think of it as a river,' May says 'but now we know it is a series of eddies.' So at some point, as it changes direction, sticking with the current will start to take you off your optimal course. 'We use the current until it becomes a loosing angle, and then we set ourselves up for the next eddy.'
Hickman agrees that it is a mistake to focus so much on staying in the current that it takes you away from the best course the prevailing wind will allow you to lay. 'If you find the current, and it is taking you in the direction you want, go with it. The rule is, never tack or gybe to get in the current. Your strategy is predominantly set by the wind, but in the absence of wind constraints you go with the current.'
'The first rule in any Rolex Sydney Hobart race is to go south at the earliest opportunity and to sail the closest angle to Tasmania that the prevailing wind will allow,' May advises. 'In recent years we've seen people heading out to sea straight off after they clear the Heads to get the current. My rule is the minute we clear Bondi we tack to head south. The continental shelf is 20 miles off Sydney but as you approach Jervis Bay the shelf closes the coast.'
It is a general truth of sailing that the shorter the boat the slower it is, and the bigger the percentage gain to be found in the current. Brad Skeggs, the skipper of the smallest competitor in the 2007 fleet, Palandri Wines Minds Eye says 'The current is super important for slower boats like ours, so we have to read the current right. But it all depends on where you want to enter and exit Bass Strait, which is effected by the current and wind at the time. We won't work it out until Christmas day when we can look at the weather forecasts and work out what angle we want to take into Tasman Island, whether to come in wide or close in.'
At the other end of the fleet the current has become superfluous. Mike Slade, the skipper of the 98 foot maxi City Index Leopard points out that in a boat that consistently reaches speeds of 26 knots, a couple of knots of set is very small beer. 'The lesson I have to drive into navigators who come from 40 footers is forget the current. We have to choose the line that gives us the fastest speed.
'We would be more likely to head offshore looking for wind, not current. And conversely we might go inshore to avoid wind or seas that will force us to slow the boat down.'
Roger Hickman points out, though, that the maxis sail a different race to the rest of the fleet. 'If you're after line honours you only have to keep yourself between the other bloke and the finish line. When you are after a handicap win you can't let off for a minute, and you are competing against boats that might be a hundred miles behind you. If you can get another 10 boat lengths more using the current it could turn out to be crucial.'
With northerlies predicted for much of the 63rd Rolex Sydney Hobart it is likely that the modern skiff-like yachts that are able to plane at speeds of 16 to 20 knots will be inclined to take the Slade approach, at least for the first two days. For the displacement boats, this year the current will come without the downside of the steep seas generated by wind against tide, and the wind constraints will be fewer.
Roger Hickman for one will be making the most of it. 'The current is free. You have to work with your sails and your gear but you get the current for free. And every yachty loves getting something for free.'