Cup Spy: August 15 - A close look at the AC75 raceboats - from the Practice Session
by Richard Gladwell/Sail-World NZ 18 Aug 2024 10:21 UTC
18 August 2024
American Magic, Emirates Team New Zealand and Orient Express - AC75 - Practice Session - Barcelona - August 15, 2024 © Ricardo Pinto / America's Cup
Two months ago the AC37 Joint Recon team disbanded and Cup fans were unable to get their daily update on what the six teams in the 2024 America's Cup were testing on their newly launched AC75s. It was a critical point at which to have the program shutdown.
It was not until mid-August that the teams again came under a camera lens, giving Cup fans and followers some insights as to changes that had/hadn't been made.
Earlier this week photographers were back on the water again shooting in Practice Sessions, specially authorised by the Regatta Director, Iain Murray, enabled the teams to sail side by side, and heading in the same direction for more than 20secs - a practice which is otherwise outlawed in the America's Cup Rules.
In the first image, Alinghi Red Bull racing and American Magic cross tacks. As can be seen in some other images, Alinghi's mainsail has bad tension creasing in its lower section, an area where many teams have focused on smoothing air flows. American Magic's mainsail is much smoother in its lower section. In the two close up views the telltales show the airflow starts getting some turbulence as the air passes over the creases, and then reattaches in the back third of the sail.
In later shots Alinghi's mainsail does look softer. Also we don't know if Alinghi is using their practice spar, or their racing one, remembering thatthe Swiss team broke one of their two racing masts on June 13, 2024.
On the jib, in one close up, we can see the Swiss team is running a twin sheet to enable fine trim control of the sail.
Staying with jib sheets we can see here that Emirates Team New Zealand has opted to stay with a single sheet which exerts a lot of downward force on the leach of the jib.
The fairings over the jib traveller don't seem to be too concerned with keeping the water out of the trench that the holds the traveller for the self-tacking jib - on of the features of the AC75 Class Rule Version 2.
Image 4: American Magic features a nice shroud fairing, with co-helm Tom Slingsby behind.
Image 5: Two cyclors take it easy between races on ETNZ with a co-helmsman positioned ahead, and the Lidar unit in between.
Image 6: Emirates Team NZ have their heel angle optimsed, to minimise leeway, by getting some push off the leeward wingfoil. The white flat object on the aft deck is probably Starlink receiver dish - used by most teams for comms/data transmission from the AC75 rather than being reliant on local networks.
In Images 7 and 8 below, in flat water - ETNZ and Alinghi are both flying low to the surface - maintaining the end plate effect between the surface, hull and rig to stop airflow under the hull and affecting the efficiency of the rig.
In Image 9 below Emirates Team NZ sailed in the Practice racing with their Lidar units on stalks to develop 3-D images of the sail shape
In the next two Images 11 and 12 we can see the different below the waterline hull shapes of Alinghi Red Bull Racing and American Magic, with the different design treatments probably a response as to how to best cope with the Barcelona seaway on a difficult day. The two images highlight the different design approaches to deck shape. The helmets/heads that can be seen on American Magic are the sailing crew, with the cyclors aft of them.
Images 13, 14, 15 and 16 shows Emirates Team NZ and Alinghi Red Bull Racing sailing upwind with the boat heeled to windward in a very controlled manner in flat water. Looking from aft the cyclors are just visible behind the two sailing crew forward. There is quite a difference in design approach to house the cyclors for each team. The bottom sections of the mainsails are also quite different.