Cup Spy: June 13 - Swiss smash rig sailing in 20kts off Barcelona
by Richard Gladwell/Sail-World NZ 14 Jun 10:46 NZST
14 June 2024
Alinghi Red Bull Racing - AC75 - Day 30 - June 13, 2024 - Barcelona © Ivo Rovira / America's Cup
The Swiss America's Cup Challenger, Alinghi Red Bull Racing broke is mast on Thursday afternoon, late into a four hour training session in a breeze of 20kts.
The Swiss became the first team to break an AC75 mast in either the current America's Cup cycle or the previous edition for the 2021 America's Cup in Auckland. Early in the previous America's Cup cycle, Luna Rossa did drop a rig on their first AC75, however this is believed to have been a structural failure around the forestay attachment point in the boat hull.
Wind conditions were below the 23.5kt maximum to start a race. The breeze from 215° was on axis with the reported moderate sea state of less than 0.8metres.
The incident occurred as the Swiss bore away, going through the so called "Death Zone" as the AC75s accelerate downwind. It was in similar conditions in the Challenger Semi-Final in Auckland that America Magic set an AC75 speed record in a race of 53.31kts, and it was likely that the Swiss were headed towards this mark.
Putting the video into slow motion, the mast can be seen to start buckling about a third height, and sail track holding the double skinned mainsail clearly starts pulling away at that point - with daylight showing through. It did not appear that there had been a part failure - the spar just appeared to start overbending to the point of a destruction failure.
While the team may claim that the conditions were "top end", they were certainly within the racing range, and Emirates Team New Zealand with less than half the 30 days sailing time that Swiss have enjoyed off Barcelona, have sailed in winds gusting to 35kts without incident.
It has been noticed that the Swiss, since launch, have been sailing with a lot of distortion wrinkles radiating from the clew in the bottom third of the mainsail, which is usually an indication of insufficient luff tension, or that the mainsail is not properly shaped to suit the mast curve, or that the mast is flexing more than the rig designer intended at that point.
However of all the potential reasons for the failure, the Swiss will be hoping that it was operator error. The AC75s are allowed two new masts, and one legacy mast for the current Cup. It is believed that the AC75 otherwise known as "Boat 2" was using a new mast, and if there was some design or structural failure, that would likely have been replicated in the second new mast shell.
The most likely cause is that the luff tension on the mainsail, controlled by two hydraulic rams was not eased by the crew or there was an electronic failure on activating the rams, keeping the induced bend in the spar. The failure looks to be a compression failure, but from the distance and angle of the video it is hard to tell anything definitely.
A spokesman for the Swiss team, Co-General Manager, Silvio Arrivabene, only spoke for half of the allowed three minutes of post session interview. Clearly he was not in a position of wanting to say too much before a team debrief, other than the usual they were thankful no-one was injured or worse in the dramatic incident. He confirmed that the Swiss had a second mast with which they had previously sailed. However there was no indication as to when the team would be able to resume sailing.
Images from the AC37 Joint Recon team, which stops operating at the end of next week, showed there was a clean break on one of the mast sections, without a lot of splintering - however another shot by the AC37 Joint Recon team revealed some cracking and splintering of the mast wall.
The usual practice would require full assessment and for the spar to be scanned by ultrasound. While the external dimensions of the mast are strictly controlled, the layup is designed by the team, however a minimum is specified in the class rule.
The team has not issued a statement on the issue or its impact on their America's Cup program.
The issues are whether the mast is repairable within the rules, and whether it can be repaired to the same characteristics as the original, and be a racing spar, rather than suitable for training only. There are almost a page of rules in the Technical Regulation covering component repairs with a key requirement that there should be no change in stiffness or performance under load. Repairs must be to the satisfaction of the Measurement Committee.
There has been no comment from other teams as to whether they will pause their programs, checking for the same issue in their spars, given the one design restrictions imposed by the rules. A further area to be checked is whether the minimum layup specification is adequate.
Alinghi Red Bull Racing - AC75 - Day 30 - June 13, 2024 - Barcelona
Alinghi Red Bull Racing rolled out their B2 boat at 9:30hrs, mast was stepped after a longer procedure of tensioning and releasing the forestay, the yacht was craned in at 10:20hrs.
After the usual dock checks, the team docked at 12:00hrs. Higher range breeze was forecasted and hence M2-1 was paired to the J4-1 just inside the harbour. Once behind the pier, B2 took off on starboard tack with the previously seen technique employing also the windward board. Breeze was measured 18-20kts from 215°.
In the first stint, B2 sailed an upwind and a downwind practicing some manouevers. B2 looked a bit overpowered and stopped to swap the J4-1 with what looked like a smaller J4. Then the team seemed to face an issue after self taking off and sailing less than a minute. Once up foilborne again, B2 started drilling some laps on the course and occasionally engaging and exchanging leads with the Italian challenger.
At 14:10hrs, after approximately 60 minutes foilborne sailing and 30 manoeuvers all four cyclors were swapped and new batteries were brought on board. The jib was lowered and rehoisted for a quick check before two additional stints were sailed around the course.
Back foilborne at 15:05hrs, B2 sailed an upwind and while bearing away on the left hand mark, a structural failure occurred buckling the new mast in two pieces at a third of its height, the rig collapsed on deck and water. The hull seemed to have not suffered any major damage beside scratched surfaces on the bow.
To recover the rig and mast pieces the sheets and main skins were cut open. As the team docked in, the hull was craned out a 16:30hrs followed by the mast pieces and main skins recovered by divers. For the day, B2 was observed with 88 minutes foilborne, 28 tacks and 21 gybes with the majority foil to foil.
[Michele Melis AC Recon].
Crew:
Sailing: Arnaud Psarofaghis (stb), Maxime Bachelin (port), Bryan Mettraux (stb), Nicolas Rolaz (port).
Power: First shift: F. Noti - N. Stahlberg - T. Schir - A. Maillefer; Second shift: F. Trub - B.Delarze - N. Theunink - A. Cevey
Session Statistics: Alinghi Red Bull Racing - AC75 - Day 30 - June 13, 2024 - Barcelona
- Weather: 24 degrees Sunny
- Wind Strength: 17-20kts
- Wind Direction: 210-215°
- Sea State: 0.5 - 0.8mtrs from 220°
- Crane In: 1020hrs Dock Out: 1200hrs
- Dock In: Not Recorded Crane out: 1745hrs
- Takeoff; Self launch; TWA: NA degrees Speed: NA
- Total Tacks: 28 Fully Foiling: 27; Touch & Go: 1; Touch Down: 0
- Total Gybes: 21 Fully Foiling: 20; Touch & Go: 1; Touch Down: 0
Additional Images:
Official Video: