America's Cup: Are you still foiling, or are you already suppressing? Favourites miss out on match points

The evening of 16 September was a curious day in the Louis Vuitton Cup. In both semi-final encounters, the favourites were 4-0 up after four races at the weekend. Everything pointed to the fact that the teams from Luna Rossa Prada Pirelli and Ineos Britannia, already the most potent in qualifying, would also be able to claim their last remaining point in the "first to win five" semi-final series of the challengers for the 37th America's Cup.

America's Cup chase: less wind, different game

But with changing conditions - instead of the furious Sunday show in 16, 17 knots of wind, only a good handful of knots were served up on the fast-flowing border to the lottery - the game of the challengers also changed. Only one light wind duel each could be fought on Monday between Ineos Britannia and Alinghi Red Bull Racing and Luna Rossa Prada Pirelli and American Magic.

A glance at the results alone revealed that these were special matches. In both encounters, it was not the favourites who won, but the teams with their backs to the wall. The British team fell off the foils in the pre-start phase. Alinghi Red Bull Racing then opened the race with a very close early start and initially had to drop back. However, it was then visibly more difficult for the Brits to stay on the foils. "Britannia" struggled mightily in the gentle breeze.

Cup veteran and TV commentator Peter Lester posed the question of whether the British might be paying a price for their dominant downwind speed in this area? The Swiss "BoatOne" had an easier time that day in the winds forecast at six to nine knots, which tended to remain at the lowest limit. For the Swiss it was a matter of Cup survival: If they lost the next race, their campaign would come to an abrupt end.

Tricky tasks, foiling impossible

In the tricky conditions, both boats had naturally set their large J1s. Both teams kept the number of manoeuvres to a minimum. At the top gate, Ineos Britannia led by 17 seconds. England's pride of sailing rounded the first leeward mark 1 minute and 10 seconds ahead of the Swiss "BoatOne". Everything seemed to be going as expected. But then, at the start of the second cross, the Brits fell off the foils again at their first tack just before reaching the course limit.

We've always said it: until you have these five points, it's not over." Ben Ainslie

The Swiss took advantage of this by mastering their first tack extremely high on the foils and taking the lead. While the Brits continued to struggle with foiling, Alinghi Red Bull Racing had extended their lead to half a kilometre when the race committee shortened the course to one nautical mile. At the second windward mark, Alinghi Red Bull Racing's lead had grown to a full kilometre. Then the Brits fell off the foils again.

The Swiss received further good news when the race committee shortened the course to five sections (instead of six). However, they fell off the foils themselves in the very next gybe. The race now continued with both AC75 foils in displacement mode. It wasn't pretty to watch, but it remained exciting. Also because it was unclear for a while whether the far leading Swiss would be able to master the course in a "crawling" manner within the time limit of 45 minutes at eight or nine knots boat speed of the otherwise easily reaching 45 knots speed foilers.

Alinghi Red Bull Racing continues to fight

When "BoatOne" finally crossed the finish line, the relief and joy on board and on the surrounding Alinghi spectator and support boats could not have been greater. The Swiss team had reduced its deficit in the semi-final of the challenger round of the America's Cup to 1:4 and thus earned itself at least one more semi-final encounter with Ineos Britannia.

Of course they want to cross the finish line at 45 knots. But eight knots is also fine if it means a win. So we'll take that." Arnaud Psarofaghis

The favourites in the second semi-final encounter of the 37th America's Cup challenger round also shared the same fate on this day. Luna Rossa Prada Pirelli also had to admit defeat in the low wind race. NYYC American Magic seized the opportunity to score the first winning point.

After a short start delay to allow the wind to freshen up a little, "Patriot" then sailed into the pre-start box on time before "Luna Rossa" followed. Both crews had observed the foiling stress and the race crawl beforehand and acted extremely cautiously. They kept a large distance from each other in order to avoid any paralysing wing beats from their opponents.

Too many penalties for "Luna Rossa"

At the start, both boats dived in from the windward side of the line. With "Luna Rossa" initially three or four knots faster, the teams opened their fifth semi-final duel with a race to the course limit. Both boats tacked at the same pace, but the Italians had the better boat position upwind and "Patriot" initially lost ground.

The pilots Jimmy Spithill and Francesco Bruni and their crew on "Luna Rossa" managed a largely error-free downwind course: the reward: a 17-second lead at the second gate. However, the "Patriot" crew then managed a decisive manoeuvre after a split: with the right of way, they forced "Luna Rossa" to react with an expansive manoeuvre at the next encounter on the course to avoid a collision. The Azzurri were awarded a penalty for crossing the course boundary.

Whilst "Luna Rossa" was recovering from the damper at the next split, there was another right of way infringement at the top of the gate. Once again, "Luna Rossa" was penalised because it came too close to "Patriot", which had the right of way, when both yachts crossed. Patriot then reached the goal with a three-second lead. The fans of both teams were now holding their breath.

Start of the Youth America's Cup on 17 September

The duel remained gripping. At the last gate, the Italians tried to lure their opponents into a right of way infringement in the two-length circle. They themselves fell off the foils, while "Patriots" pilots Tom Slingsby and Lucas Calabrese generously and safely rounded the mark with their boat. They then steered American Magic flawlessly to the first victory point at the finish. The Luna Rossa Prada Pirelli Team is now also 4:1 in favour in this semi-final duel. Like Ineao's Britannia, the Italians have three match points.

The semi-finals will continue on Wednesday (18 September). Before that, the Unicredit Youth America's Cup begins on Tuesday (17 September) at 2 pm with the first four fleet races for the Pool A teams with mother teams in the current 37th America's Cup. Click here for the live broadcast. Like the semi-finalists in the Louis Vuitton Cup, the AC Team Germany youth crew will be competing in four fleet races with the Pool B fleet for the first time on the Cup course off Barcelona from Wednesday. These races will also be broadcast live.

Replay of the semi-final duels in the Louis Vuitton Cup

Louis Vuitton Cup, semi-final, race 9 - Alinghi Red Bull Racing vs. Ineos Britannia:

Louis Vuitton Cup, semi-final, race 10 - NYYC American Magic vs Luna Rossa Prada Pirelli: