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The huge foiling monohull designs under development for the 36th America’s Cup, the pinnacle of yacht racing, will push both technology and human limits for the teams competing in the March 2021 event in Auckland, New Zealand.

As the rules governing racing yacht construction have evolved over two centuries, the teams vying for sailing’s top prize have striven for ever-increasing speeds while advancing the responsiveness and agility of their crafts. The AC75 Class Rule defines the parameters within which teams can design a yacht eligible to compete in the 36th America’s Cup.

American Magic turned to Luna Innovations, a leading provider of fiber optic sensing technologies for the aerospace and automotive industries, to address its need for on-board instrumentation to evaluate critical structural components, inform sailing tactics and ensure safety.

A new era of foiling

The incorporation of hydrofoils — lifting surfaces that allow a boat’s hull to glide above the water — is among the most important developments in modern yacht racing. A new era of foiling that commenced within the Figure 1. DEFIANT under sail in Narragansett Bay, Rhode Island. Source: Amory Ross/NYYCpast decade has allowed average speeds for America’s Cup competitors to jump from 10 knots, or 11.5 mph, to numbers four times greater and rising. The AC75 Class is expected to reach speeds around 50 knots, or 57.5 mph.

Hydrofoils used on watercraft are not unlike the airfoils used to create aerodynamic force on aircraft. Foils provide lift, but increasing speed and efficiency also relies upon overcoming the corresponding drag in the ship’s wake. Success in this context is dependent upon factors such as foil shape and configuration.

Because there are complex and atypical geometries involved, even the smallest components tend to be custom-made. Put simply, every boat is a prototype, and the design cycle is a proving ground for limits of racing itself.

In addition, the emphasis on creating the fastest craft has a huge impact on the sailors’ safety. Custom engineering and construction with new materials requires advanced strain sensing capabilities in both the design and in situ phases.

With high stakes and individually focused designs, securing financial sponsorship from aerospace engineering firms has become a key strategy for yachting clubs. Sponsorship represents one component of attracting investments in the hundreds of millions aimed at designing winning vessels. Relationships with aerospace partners also offer an opportunity to apply learnings from airfoil designs.

For the New York Yacht Club (NYYC), the club with the most America’s Cup wins and, from 1851-1983, the longest winning streak in sports history, the upcoming 2021 competition presents an opportunity to expand upon the high-tech components of its competition boat, DEFIANT. NYYC is entering the race as part of a joint venture that goes by the name American Magic, a nod to the club’s storied history as creator of the boat that gave the America’s Cup its name, and the original defender of the Cup first awarded in 1851.

“DEFIANT is the first America's Cup class boat built to represent the New York Yacht Club in more than 16 years,” said Terry Hutchinson, skipper and executive director of American Magic.

“To compete in the cutting-edge AC75 foiling monohull class, our partners must be able to provide expertise in advanced material measurement and apply it to the intricacies of racing yacht construction. Luna’s experience with America’s Cup racing events as well as the aerospace industry makes it an ideal partner.”

Advanced strain and load change monitoring

Both the challenge of measuring custom-built parts and the environmental demands of the sport itself provide an ideal use case for fiber optic sensors, which can be deployed as multiple sensing points on a single, flexible fiber. In addition to being extremely lightweight and low profile, fiber optic sensors and the associated cabling are electrically passive and corrosion-resistant, making them particularly well suited for the harsh onboard conditions.

Luna Innovations, with its 2018 acquisition of Micron Optics and its industry-leading optical sensing and high-speed dynamic measurement capabilities, represented an ideal choice as a technology partner. Micron Optics has worked on racing yachts since 2003, as a partner for teams throughout Europe, Asia and North America.

Figure 2. Luna’s Micron Optics single board interrogator (above) and ODiSI 6000 optical distributed sensor interrogator (below) represent two complementary devices of a robust product suite. Source: Luna InnovationsThe resulting expansion of Luna’s product range included the HYPERION Single Board Interrogator, which in the yachting world has long been employed to provide data during the design cycle as well as in-situ readings during sailing practice sessions and the race itself. Under sailing and race conditions, its small footprint, wide sensors count capacity and industrial proven reliability offer real-time focus on key data points, with fiber optic sensors embedded directly inside the boat's structure to provide strain and load change monitoring.

Luna’s contribution did not stop with the HYPERION. Because the design cycle does not carry the same limitations as the in-situ phase, the American Magic team has been able to leverage the capabilities of the ODiSI 6000 high-definition distributed sensor interrogator to test parts before using them on the boat. The ODiSI offers ultra-high-resolution data, providing a more complete and detailed picture of the foil strain field, which is especially useful in developing and validating advanced structural models and simulations.

Taken together, the HYPERION and ODiSI represent two complementary devices of a robust product suite that is a natural fit for the yachting industry. The ODiSI delivers the high-definition data for in-depth analysis and design optimization, while the HYPERION provides a streamlined solution for real-time analysis of performance during sail and racing. Not surprisingly, other industries, such as aerospace and automotive, are adopting this range of measurement solutions that scale from design through operation.

“We are excited to partner with the American Magic team and thrilled that they will use both the HYPERION and ODiSI systems,” said Scott Graeff, president and CEO of Luna Innovations. “The capability and expertise to deploy both high-speed and high-resolution systems to optimize strain measurement is game changing for Luna and our partners.”

As for the America’s Cup, the sailing world will wait until 2021 to gauge the success of the many design experiments that teams around the world are currently pursuing. These experiments are happening on a wide variety of components, ranging from hydrofoils to composite materials to data collectors. Luna, with its comprehensive approach to fiber optic sensing that can be applied to vehicles of all types, is already a leader in the race.