Ainslie revels in underdog role as Ineos Britannia plot fightback

Twenty-four hours can be a long time on the water. When the sea state off Barcelona changed on Tuesday, the balance of the 37th America's Cup shifted with it. All of a sudden, Ineos Britannia, who were trailing Emirates Team New Zealand 4-0 in the best-of-13 series, were swept back into contention. The America's Cup is a competition for sailboat builders as well as sailors, and the subtle design differences between the two AC75 yachts gave the British team an advantage in the heavier weather. Soon enough, they had pulled the score back to 4-2.

- Andy Bull

One of the key reasons New Zealand had the edge in the calm seas during the opening days of the regatta was because their design team chose to optimise the boat's performance in flat water. Their boat, Tahoro, has "dry bulbs" on its foil arm, to ensure their foils meet the stipulated weight while also minimising the amount of surface area in the water. It works when the waves are flat, but when the seas are up, the design puts them at a disadvantage.