"The first reason was obvious - that it would be faster, and surprisingly given later events, foiling was also safer, noting that calculations showed that a conventional multihull of the AC72 type would be difficult in winds above 18kts, and even more so in a bear-away situation." "In another series of load diagrams, Wilkinson elaborated on the forces operating on the AC72s, particularly around the foil cases with a lift of about six tonnes, a lateral force of seven tonnes, and a staggering 22 tonnes at the pivot point of the foil and 16tonnes on the control ram at the top of the foil - all contained within the AC72 hull structure."
"A couple of moments of truth for the US team were the nosediving incidents, the first of which wrecked the wingsail and almost completely destroyed the boat. The second had less dramatic results but was a significant learning experience. One of the tools used to analyse what happened in these incidents was a multiple moving plot of the data gathered from various key readout points, which would enable the forensic team to look at how the various elements interplayed, together with similarly time stamped video. In the example shown a nosedive incident was created when the afterguard tried to adjust the foil pitch control using hydraulics, which at the critical moment has lost pressure - the readout showed that a wingsail twist adjustment was being done at the same time draining the hydraulic pressure to the point where the foil control failed to work - triggering some re-design work to avoid a re-occurrence of the issue. In fact four changes to the hydraulic system were made to avoid a re-occurrence of this situation"
"Oracle improved upwind drive through increased lower aft loading. (interestingly this significantly increased the wingsail trim sheet loads, and the subsequent hydraulic demands required the crew to grind hard to maintain power from the race start to the finish)"
