America’s Cup 2021: Paul Lewis – The key dates that could play a role in deciding the America’s Cup


Mark down January 13 as a key date in this America’s Cup – when challengers first have to declare their foil wings.

The decision over which foils to use rates as the most vital ahead of the Prada Cup Challengers’ Series, beginning on January 15. Yes, the teams have to decide what foils they will be using two days ahead of racing.

That means they either have to be highly enlightened at predicting the weather or their designers very good at producing foil tips competitive across a range of weather and wind speeds.

Unlike the last Cup regatta in Bermuda, where foils could be applied on race day according to the weather and sea conditions, the rules have changed this time, agreed by all challengers. They have to declare foils well ahead of racing – five days ahead in the case of the Prada Cup final and the Cup match (between Team New Zealand and whichever challenger wins the Prada Cup).

While the foil arms and the canting system which lifts them up and down are one-design, the foil wings or tips are a crucial area where designers have scope for interpretation. The design imperative: to produce all-purpose foils rather than specific ones for light or heavy airs.

There are two main rationales: cost and convenience. In Bermuda, teams could change their foils daily – but that meant getting measurement committee officials down to every boatyard to check the rules were being observed every time; it took many hours and a typical America’s Cup “arms race” as teams had to have a small arsenal of foils available, at enormous cost.

These foils are said to take 2-3 months to develop and cost estimates range from $300,000 to well over $1 million each.

Designing foils which can operate at an optimum level at all stages of the Cup wind limits (6.5 knots at the bottom end; 21 knots maximum) is no easy task – but the team that produces the best all-purpose foils will likely win the Cup.

Many commentators have already noted Team NZ’s T-shaped foils as opposed to the Y-shaped foils of the challengers; you can bet your Christmas turkey teams are working as hard as can be to modify their existing foils by the 20 per cent permitted by the rules.

The teams are allowed only six foil wings (three sets) in total; logic suggests numbers five and six will be the premier race foils after development. The eagle-eyed will have spotted Team NZ racing with two different foil wings attached on occasion – testing which performs better in what circumstances or simply not giving much away at this stage.

Yachting gossip has it that Ineos Team UK have already used up their six foils and are thus unable to produce new, hidden ones. Other bar chatter suggests that Luna Rossa and Team NZ have one set of foils up their sleeves.

While foil wings will be hugely important, there are other vital variables. Hull shape can be modified a little within the rules; the double-skinned mainsails, rudder wings and foil flaps are all open design. The flaps are like those on an aircraft wing, computer-controlled, tuned on race day for weather and wave conditions and with an influential role in take-off, smooth flight and avoiding splashdown.

This is new ground for everyone – and we have already seen from the early racing that the AC75s wallow like pigs in mud when the wind drops too low. This is also a La Nina summer, meaning the wind in February and March could drop away more than normal.

The big hurdle for the challengers is to get through the Prada Cup – and the higher wind conditions that might apply then – and have foils also competitive enough to take on Team NZ in what could be lighter airs.

So, what do we know about the teams’ foils so far? Not much. We know that foils plus hull shape go into the design equation to solve the biggest aerodynamic and hydrodynamic question – how to get up on the foils quickly, how to stay there and how not to be too “sticky” when the boat does touch down on the water?

Team NZ seem to have smaller foils, able to get up on them faster. Ineos Team UK are highly competitive in a straight line in high winds but so far look horrible in low winds and manoeuvres. Luna Rossa seem to be better in light winds while American Magic, also with smaller foils, seem good in both but maybe better in higher winds.

There’ll be feverish activity in the boat sheds, deciphering the mega-Gigs of data and making modifications, especially of the foils. We’ll get our first real clues on January 15 and if, in March, all challengers have gone home without the America’s Cup, we’ll know they have been, well, foiled.

Foil declaration dates

Prada Cup round robins and semifinal

January 13 – these foils must be used for three days of racing on January 15-17
January 20 – these foils must be used for three days of racing on January 22-24
January 27 – these foils to be used in semifinal (best of seven races) from January 29-February 2

Prada Cup final

February 8 – foils to be used in best-of-13 series from February 13-22

America’s Cup match

March 1 – foils to be used in best-of-13 series from March 6-15

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