According to a report posted on the Valencia Sailing website, Alinghi has been testing a very black mainsail.

To the untrained eye, this is one of the most visible developments so far in this Cup (with the hull shape of NZL 84 and Alinghi/Oracle's jumper-less rigs and bowsprit).

The jumper-less rig reduces drag while the black mainsail is believed to be constructed a little differently to get the sail to hold its shape better.

"We understand the black mainsail, there is a potential weight gain," Grant Dalton commented. "It is still built on a mould but it is a lot of patches of a particular type of filament which, when you add them up, gives you a weight gain.

"The mainsails they have used have had structural issues but they will solve that. Is it an advantage? Possibly. We discounted jumper-less rigs a while ago."