Cup Spy: Emirates Team New Zealand breaks sail in training under shock load
by Richard Gladwell/Sail-World.com/nz 19 Apr 2023 16:01 AEST
19 April 2023
Emirates Team New Zealand - AC75 - Hauraki Gulf - April 19, 2023 © Justin Mitchell
Emirates Team New Zealand suffered a sail breakage on the Hauraki Gulf while training for the second day, in a fresh onshore breeze and moderate sea state.
In a later interview, skipper Peter Burling confirmed the team had been sailing with their J2 headsail, the second largest jib in their sail wardrobe - which had been deployed after the wind eased. However that lull proved to be temporary and the breeze increased later in the session.
Just before the breakage a crew member can be seen crawling forward and making an adjustment to the jib, he is still there as the jib tack tears, and the sail blows back against the mast.
While sailing to windward and foiling into a sea-state which is a mix of swell and windchop, the J2 seems to have been used outside its range, and the tack tore out of the sail, blowing it back against the rig as the AC75 heeled to windward under pressure from the port wingfoil.
According to Burling the crew were able to get the speed off the AC75, which was probably sailing to windward at a speed of 30kts or more.
At the time of the incident the nearest wind observation from Predictwind (Rangitoto Light) showed an average breeze of 18kts gusting 22.5kts (that particular wind station has an elevation of 15metres - so will read a little high).
Prior to the incident around 1300hrs, the breeze had dropped to 16kts and was trending down.
It is not know whether the team will train tomorrow, in these conditions - which are a valuable learning opportunity for the design team and engineers to obtain performance data on an AC75 sailing in a Barcelona style seaway in fresh breezes.
The AC75 was probably sailing in an apparent windspeed of 50kts apparent wind, and one of the challenges for sail designers and engineers has been to develop jibs, in particular, that will work across a wide range - to develop the power to get the AC75 to self-launch onto its foils, and then be capable of taking the increased stress and the apparent wind increases dramatically. Take-off boat speed is reckoned to be around 15-16kts, and the top end speed sailing to windward in flat water under foiling conditions is 36kts plus.
The sea state will add considerably to the shock loading on the sails and rig - and the data gained is is new territory for all America's Cup teams - of which only three have sailed AC75s to date, in the current America's Cup cycle.