Luca Rizzotti, founder of “We Are Foiling”

JEC Composites Magazine: What are foils?
Luca Rizzotti, founder of “We Are Foiling”: Foils are submerged aerofoils that generate lift. In conditions of adequate speed, the surfaces can generate such lift as to allow the hull to exit completely from the water, significantly reducing friction. The decrease in friction corresponds to a consequent increase in speed.

The principles of foiling were first understood in 1861 by Thomas William Moy, an aeronautical pioneer who wanted to test flow turbulence on wings and applied it to a horse-drawn boat on the Surrey Canal. However, the credit for having developed the first boat capable of navigating on foils autonomously goes to an Italian, Enrico Forlanini. In the last twenty years, with the availability of lighter composite materials combined with the greater capabilities of CFD programs, foiling increasingly took hold in the nautical sector, first in the sports arena such as in the America’s Cup, then spreading to every sector.

JEC Composites Magazine: You are the founder of an association called “We are foiling”. What prompted you to create it and what are the purposes?
Luca Rizzotti: It all started in 2014 when “Moth”, a small foiling monotype of less than 4 metres, was born at the same time as the giant foiling multihulls of almost twenty metres that would then be used in the America’s Cup, the maximum technological expression of sailing sports. I thought that: “The future of sailing lies in these fifteen metres of difference” and, together with a group of enthusiasts, I set about building what would later become “We Are Foiling”, an ecosystem of connected events closely related to foiling, the new era of modern sailing in search of new forms of sustainable mobility on the water.

JEC Composites Magazine: How did we evolve from canting keels to wings?
Luca Rizzotti: It is a completely new configuration on the AC75, jointly proposed by ETNZ and LR in 2019 for the AC 36. The system allows the use of one foil as a lifter and the other as a righting moment. The efficiency of this configuration can be seen in the speeds expressed by even the smallest AC40s that exceed 50 knots.

With AC40 and AC75, we mean the so-called America’s Cup class boats respectively 40 feet, which will be used for the first preliminary regattas and for the Youth and Women America’s Cup in 2024, and 75 feet, which will be used for the last preliminary regattas, for the Challenger Selection Series and for the America’s Cup 37 that will take place in October 2024 in Barcelona.

AC 36 refers to the 36th edition of the America’s Cup, which took place in Auckland (New Zealand) in 2021.

JEC Composites Magazine: How do you design a foil?
Luca Rizzotti: Foils are nothing more than wings and use the same aerodynamic principles. We can speak of a wing when a body in motion with respect to a fluid has a shape such as to minimize the resistance to advancement and is indeed subject to a series of fluid dynamic actions capable of generating sustenance and/or the displacement of the body itself. To develop the foils for a boat, the designers use computational fluid dynamics (CFD) software and other ad hoc tools that each design studio or each America’s Cup team has developed over the years. The aim is to visualize and simulate the flow of the fluid on the surfaces and to compare different configurations to reach one’s goal.

JEC Composites Magazine: What are the materials used in construction and how are they used?
Luca Rizzotti: The materials for the construction of foils are different: the most used material is high-modulus prepreg carbon fibre post-cured in an autoclave. Special technologies are also used for the Imocas – such as those of Avel Robotics – for the production of carbon foils. Persico, one of the leading shipyards in the production of foils, built the rig used by the teams in the last America’s Cup and most of the foils used by the latest Imocas. Other well-known shipyards are Multiplast and Mer Concept in France, while in New Zealand SailGP Technologies builds the foils for the F50 catamarans and for many other boats.

JEC Composites Magazine: Can you explain the conceptual and design differences between sailing and motor foilers?
Luca Rizzotti: The main differences between the foils used on motor and sailing boats are of two types. Currently, the foils used in the sailing world have mainly a competitive purpose, they are therefore designed to obtain maximum speeds even at the expense of stability. They also operate in a particularly complex system, where changes in wind intensity and direction lead to important variations in lift and angles of attack. When used with motorboats, on the other hand, speed regulation is a “fixed” element that can be easily followed by foil regulation software. Furthermore, the stability of the foils is typically a more important factor than the maximum speed obtainable, so that one of the main reasons for their success is comfort.

The evolution of foils is continuous and very rapid. In general, foil builders will go towards greater ease of use, both in terms of design and through mechatronics.

JEC Composites Magazine: Why is the environmental impact of foil/engine hybrids lower?
Luca Rizzotti: As speed increases, thanks to the foils, the hull rises from the water and the friction between the hull and the liquid is reduced only to the part still immersed, and therefore very often only to the appendages. A decrease that can even reach 90% of the energy needed to push the same hull in displacement mode. Therefore, at the same speed, we can speak of a reduction in consumption often exceeding 60% or, at the same energy used, of a significant increase in speed with a drastic reduction in travel times and therefore… in consumption.