Defender Oracle Team USA and challenger Emirates Team New Zealand are racing for the America's Cup on San Francisco Bay. Their so-called "September showdown" features two races daily and started Sept. 7.
The trophy winner will be the first to attain nine points.
For the Kiwis, that means winning nine races and for Oracle it means 11 race wins.
On Sept. 3, an international jury imposed a two-point penalty and a $250,000 fine on Oracle after some of its members improperly modified AC45 yachts in 2012 during America's Cup world series regattas. In August, Oracle voluntarily withdrew from the last four of those regattas.
Both teams need to avoid some of the previous on-water, hard-to-predict breakdowns with their lightweight powerful 72-foot-long boats.
The 11-man AC72 teams compete in the challenging, complex-composites-laden, development-class boat with wing sails and hydrofoils.
Speeds can exceed 52 miles per hour. As a result, boat control, material and mechanical integrity and problem avoidance are critical factors.
Oracle-owned Core Builders Composites Ltd. has built ― and as needed, rebuilt ― the team's AC72 wing sails in Warkworth, New Zealand, and, as required under AC protocols regarding country of origin, produced the defender's hulls in a warehouse on Pier 80 in San Francisco.
T.P. Cookson Boatbuilders Ltd. of Glenfield, New Zealand, builds the Team New Zealand hulls, and Southern Spars and Rigging of Rosebank, New Zealand, manufactures its wing sails.
Team New Zealand won the official challenger rights by defeating Italy's Luna Rosa Challenge, 7-1, in the Louis Vuitton Cup series that ended Aug. 25.
Both teams had problems.
The Luna Rossa team refined its daggerboard and lifting post in advance of the series, but a daggerboard problem before the first race ultimately ended the team's effort after the first mark rounding. Luna Rossa skipper Max Sirena said a polymer-matrix composite part of the lifting system broke, fortunately during a reaching leg and not a riskier jibe.
The port bow buried the structure up to the main crossbeam, reducing the boat speed and flicking crewmembers Rob Waddell and Chris Ward overboard. A team chase boat recovered the two grinders.
The rush of tons of water, however, tore the port-side fairing off the main crossbeam, sheared away bits of polymer-matrix composite components and left the crew shaken.
In race two, Team New Zealand experienced problems with electronic circuitry that controls the boat's hydraulics and was unable to finish. As a result, the team replaced all of its batteries.
In race three, Luna Rossa had to slow at the beginning of the third leg, and eventually withdraw, with damage to a sheave on the control arm of the 131-foot-tall wing sail.
The line controls the twist profile of the wing, comes down to the base of the wing and wraps around sheaves. The sheaves moved and caused the problem with the tension of the control line.
Earlier problems also had emerged.
On Aug. 6, partial peeling of Clysar polyolefin shrink film off the frame of the Luna Rosa's wing sail hindered but did not stop the team from defeating Artemis Racing of Sweden in the first semifinal race of their challenger series. The plastic film began peeling off the frames to which it is glued before the start of the race and was held in place temporarily with tape.
On May 9, Artemis Racing's first AC72 broke apart during a practice. A polymer-matrix composite girder in front of the wing sail failed, one of the two hulls snapped and the mast came down. A crew member was trapped underwater for about 10 minutes and died.
During Oct. 16, 2012 training with its first AC72, the Oracle boat capsized, pitch-poled and broke its wing sail. Repairs and component replacement cost Oracle months of on-water training time.
Oracle defeated a Swiss-based team to win the 33rd America's Cup in Valencia, Spain, in February 2010 and selected San Francisco as the host city for the current series.
The competitors mutually characterize the course as having great sea breezes, changeable current and wind conditions, and a venue with multiple on-water and shoreline San Francisco Bay viewing locations.
NBC and NBC Sports Network are broadcasting the finals live with replays available on the America's Cup YouTube channel.