Team New Zealand believe the forces involved in their recent training nose-dive were 70% larger than their previous worst crash.
The ETNZ are repairing their AC40 test boat after it suffered significant bow and deck damage in the crash and subsequent capsize that came after they lost rudder control at 40 knots and pitch-poled last week.
The design department has done a significant debrief that will see structural strengthening to the bow area of the AC40 that will be used by all teams in the women’s and youth America’s Cup in Barcelona in 2024 as well as by Cup syndicates in lead-up regattas before they switch out to the full-scale 75-foot foiling monohulls.
With all of the Kiwi team’s boats carrying numerous sensors, the designers and engineers have been able to record the forces in crashes during the 2021 Cup campaign and now on the AC40. The latest crash went next level in terms of the forward and side forces involved as the boat came to a shuddering halt while it was doing over 40 knots.
The engineering team determined that as the rudder came out of the water and control was lost, the boat spun around its foil and gybed as it was crashing, with the twist heightening the damage.
A structural engineer explained
“Not only did we see longitudinal decelerations 70% higher than the previous worst-case, but this was coupled with a simultaneous lateral loading of similar magnitude – the yacht came to a complete stop and yawed 90 degrees in just over a second,”
“We believe it was this combined load state that led to an initial failure of the foredeck sandwich panel.
“The damage we saw in the hull and partial detachment of the bow structure is likely a consequence of the compromised deck panel, rather than a root cause.”
The engineers have designed an internal structure upgrade package that will be rolled into all current and future AC40 yachts. They feel that will help the state-of-the-art boat handle the increasingly dynamic performance as it is pushed harder and harder by the world’s best sailors.
The upgrades will be produced by McConaghy’s in China, who are building the fleet of AC40s, and shouldn’t affect the delivery schedule.
They will be retro-fitted to the three AC40s already delivered – two to Team New Zealand and one to challenger of record Team UK.
Team UK are also operating their own test boat, dubbed the Silver Arrow, which has undergone tow testing and now had its mast and rigging added at their training base in Palma, Mallorca.
Italian challengers Luna Rossa have had issues with their own test boat, dropping a mast on land, costing them important development time.
American Magic continue to train in Florida using a modified AC75 from their Auckland 2021 campaign. Their latest sessions have concentrated on using a larger mainsail in an effort to find a solution to the lighter airs and choppy sea states that could be a factor in Barcelona.