America's Cup Rialto: October 21 - American Magic's Patriot's hull does the trick
by Richard Gladwell, Sail-World NZ 22 Oct 2020 11:08 AEDT
20 October 2020
Patriot - American Magic - Waitemata Harbour - October 21, 2020 - 36th America's Cup © Richard Gladwell / Sail-World.com
American Magic had an extended sail in the newly launched AC75, Patriot on Wednesday heading out well beyond the 2000-2003 America's Cup course, in a steady sea breeze of 12-15kts, and bright sunshine.
The AC75 left the dock late morning returning four and a half hours later. There was no wind initially and the team representing the New York Yacht Club, towed out of the Waitemata having to wait for an hour or so in the Rangitoto Channel waiting for the seabreeze to fill in.
The royal blue AC75, which was only launched last Friday, has now sailed on three of the five days intervening. She sailed for the first time late Friday afternoon performing some spectacular aquabatics after the light breeze rapidly increased to 21kts. After taking the weekend off, she sailed again on Monday morning - returning to avoid a fresh breeze which stayed in for the afternoon.
Today's condition were ideal for speed testing - a steady seabreeze that was new today - meaning that the seaway which often accompanies wind from this direction had not had the time to build. After sailing a long upwind leg 12-14nm, well past Tiritiri Matangi island, Patriot entered the Waitemata in less pressure than it had enjoyed offshore, with the 850ft volcanic cone of Rangitoto Island breaking up the seabreeze.
At the launch ceremony on Friday, no-one was too surprised to see that American Magic had opted to switch from the scow-style hull of their first AC75 Defiant to a skiff-style of hull design in the same genre as Italian challenger Luna Rossa and the New Zealand defender, Emirates Team New Zealand.
But as we reported on Friday, Patriot has nice simple design lines, which disguise some quite complex hull shapes.
Viewed from a distance ashore Patriot's hull shape revealed its nuances, and how those work from a sailing perspective.
The flared bow was discussed on Friday's AC Rialto, and proved its worth in the nosedive phase of aquabatics late Friday afternoon.
Out of the water on Friday, Patriot appeared quite full in her forward sections, running from the mast to the bow, and then with a scalloped hull shape running through to the transom.
In the brief period we observed Patriot returning to the Waitemata, their design team's approach and rationale became apparent.
The forward sections have been shaped in such a way that if Patriot does make contact with the surface, the volume in the forward section of the hull cuts in quickly to provide the buoyancy to get the AC75 back on her feet. Normally this design solution would throw a lot of water, which used to happen on Defiant, but doesn't appear to occur on Patriot.
In the final stage of the session today, Patriot came down the Rangitoto Channel on port, passing Bean Rock and gybed halfway between the 135 year old light house and Orakei Wharf before sailing up the harbour. She had what appeared to be a #3 jib hoisted - the correct sail for the 15kt seabreeze, but underpowered for the conditions in the harbour when a #2 jib, or even #1 jib would have been best to cope with the fickle breeze.
Patriot, like Defiant, sails with the bow down, heeled to windward stance that is favoured by the AC75 helmsmen and flight controllers. The deepest part of the hull, underneath the mast step was close to the water but didn't make contact. During the gybe, Patriot stayed close, and made the briefest of touches during the most critical phase of the manoeuvre - a few seconds after the gybe is complete and the transition is made from being on two foils during the gybe, back to where the new foil provides the required lift, and the old foil provides righting moment.
The point where the old foil is lifted clear of the water (and has contributed only drag with no lift in the final stage of the foil arm raising), is usually the point when an AC75 will splashdown. If there is no splashdown, then the crew have achieved an elusive dry tack/gybe.
Patriot did appear to lose ride height at this point and the underside of the hull appeared to come into play. But there was no sign of spray or white water, where the hull made surface contact, and after a second or two, she was up and away again.
The cutaway in the aft end of the hull sits well clear of the water, offering no potential for drag, and allowing the front half of the hull to back up the foils and do any heavy lifting required.
As the AC75 sailed away from our camera position the hull perspective changes confirming what we saw leading up to the gybe.
The verdict?
While there were some aspects of Defiant, that we liked, at first glance Patriot looks to be a significant improvement.
The British are expected to be the next to sail, followed by Luna Rossa.