The story of the 1970s sailboat that glided at 30 knots

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Exocetus Volans
Exocetus Volans

Sometimes the hybrids are brilliant insights, other times, however, they are specimens destined to remain unicums, singular experiences seemingly failed, but perhaps not too much either. This hard-to-define case received a clear response from an unreceptive market (understandably, perhaps). But the single attempt survives, and the result is undoubtedly one of the most iconic, peculiar and improbable hulls of the last century. It is theExocetus Volans, the sailboat that ran as a motor-powered offshorer. A boat so distinctive that judgments come less, what counts is experience.

Exocetus Volans, more than just a motorsailer

Other times and other minds. It was 1976 and the LAG Nautica shipyard conceived the “monster,” a very specific commission made to an equally specific engineer: Renato Sonny Levi, former RAF pilot and wizard of fast hulls. Thus was born the story of one of the most distinctive hulls ever, a planing motorsailer strong in excellent performance both under sail and power. The recipe is almost simple: 480 horsepower, mast, running rigging and sails, strictly planing hull. The goal is one, 33 knots of speed under motor, 8 under sail. Much easier said than done….

Exocetus Volans
Exocetus Volans

Exocetus Volans – Design Issues.

Problem number one immediately arises: how do we combine the volumes and lines needed for sailing with the minimal surfaces and strengths of an offshore-type planing hull? A planing hull, in fact, requires minimal hydrodynamic resistance, a sailboat, as well, if you will, but by necessity requires larger submerged volumes, just think of the centreboard and rudder. Elements decidedly at odds with opposite needs. In short, a not inconsiderable puzzle in that the elements of one are a necessary problematic in the realization of the other component, and vice versa.

Then there is the issue of rigging to come into conflict. Necessarily, mast and fixed rigging are a bulky body. A body that is not only bulky, but also problematic: on the one hand, the stresses given by high speeds could undermine its integrity; on the other hand, they increase its center of gravity, offer immense aerodynamic resistance, and result in considerable imbalance, a problematic lever in terms of agility. In short, it is a matter of designing a complex in which the components necessary for the two purposes can be married to each other without overly hindering each other. Nothing could be more complicated.

Exocetus Volans – The Project

The obstacle seems insurmountable, but let us remember that at the helm is Levi, in his own way, a genius. To address the issues then, the primary solution focuses on the hull and its volumes. Sections are given by geometries that are necessarily flattened but strong with very important edge sections. A compromise that provides good efficiency in planing, but at the same time can adapt to the displacement navigation of sail propulsion.

Exocetus Volans
Exocetus Volans – Flatbeds

The problem of drift, on the other hand, and the resulting resistance, is instead solved by a solution that is as trivial as it is efficient: just adopt a tilting blade, exactly as on many vessels rather than on some IOR designs, which were then still well established. The keel, on the other hand, is perhaps the most distinctive aspect, with the edges directed yes upward toward the transom, but strong with a straight course to act as a counter keel, concluded in a stern step flanked by two adjustable flaps. Solution that not only allows trim adjustment on glide, but also excludes surface propellers from hull-generated turbulence. Because, sure enough, to make the hull glide there were two surface propellers driven by 240 horsepower each…

Exocetus Volans

To compensate for the absence of drifting ballast, that long keel course, fully ballasted, always took over. Obviously, the solution was not enough, reasoning that several seawater tanks functioned as ballasts and adjusted as needed. Finally, the rudder, was itself adapted, tapering downward, specifically to reduce friction in planing phases.

Exocetus Volans – Propulsion and Rigging

In terms of propulsion, seeing the greatest compromise was rigging. Out of necessity, the mast was from the very beginning greatly reduced, resulting in a minimal sail area, however sufficient for the hull to reach sailing speeds of 8 knots and angles to the wind of even 30°.

Motor speed, on the other hand, was a far more satisfying affair, with 33 knots of top speed in glide thanks to the thrust provided by the two 240-horsepower Fiat AIFOs, for a total of 480 total horsepower.

Exocetus Volans at Venice-Montecarlo

Designed for mass production, the boat never saw much public acceptance, remaining exclusively a one-off, futuristic prototype. In 1992, in compensation, stripped of rigging and sail rig, it participated in the Venice-Montecarlo offshore race. It collided with a submerged object at a speed of 37 knots, contact that forced it to retire. To this day, without a mast, it still sails as a speedboat.

Exocetus Volans – Data Sheet

Length Over All (LOA) 11.89 m
Length at Waterline (LWL) 9.14 m
Baglio Massimo (B.max) 3.96 m
Fishing 0.51 m
Full load displacement 7 t
Motorization 2x AIFO Diesel (FIAT) 240 hp
Overall power 440 hp
Maximum motor speed 33 kn
Maximum speed under sail 8 kn
Builder’s Yard Lag Nautical
Main material Lamellar
Project Renato “Sonny” Levi + Franco Harrauer

 

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