More info on the unusual bulge on the centreline of the hull:
https://thespinoff.co.nz/sports/06-09-2019/launching-the-whale-at-the-unveiling-of-americas-cup-boat-te-aihe/
@thespinoff.co.nz said:
Most surprising of all is a sort of bulge running the length of the bilge, a bilge bulge, like an undercarriage...
Being a lot heavier than the catamarans of the previous America’s Cup, it’s a harder boat to get onto its foils. So – as I understand it – the dolphin belly serves as a kind of smaller, secondary hull, minimising drag in that awkward phase between foiling and not foiling.
During those not-slow, not-fast times, “it’ll only be that bit in the water, and that part is far more like a multihull shape”, said designer Dan Bernasconi...