Exocetus Volans: recipe for 30+ knot offshore sailing

Sometimes some seemingly crazy ideas are realized, resulting in something brilliant. Other times ingenious ideas are realized, resulting in something crazy. Neither the starting point nor the ending point are well defined in this case, not in this sense at least. Certain is the result, a unicum: theExocetus Volans, thea sailboat that ran like an offshorer. Or, if you prefer, the only offshorer who also goes sailing.

Exocetus Volans: recipe for a sailing offshorer

Other times and other minds. Genoa Boat Show, 1976. Renato Sonny Levi received a commission from LAG Nautica shipyards and began to conceive the “monster.” Thus was born the story of one of the most distinctive hulls ever, a planing motorsailer strong in both sail and motor performance. The recipe is simple, 480 horsepower, one mast, rigging and sails, planing hull. The result is less trivial, 33 knots under motor, 8 under sail. Easier said than done. In short, here is the story of the only sailboat that ran the Venice-Montecarlo offshore race.

Exocetus Volans – Design Difficulties.

The first challenge to be faced in the conjugation of sail and motor (planing) is contained in the necessarily different water lines. A planing hull requires minimal resistances, a refined surface study because the smallest possible component of these functions as a hydrodynamic brake. On the other hand, a sailboat requires a centreboard, to avoid drift, as well as a larger rudder blade, as well as quite different submerged volumes. A first puzzle, as the elements of the latter are a necessary problematic in the realization of the former.

In turn, the mast, becomes a major problem in the glide phase, not only in that it involves a major influence in terms of center of gravity, but as a surface that can suffer in no small measure given the stresses to which it would be subjected by gliding at 30+ knots. 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.

The article continues below

You might also be interested in:

Arriva il Pardo GT65! È il 20 metri per crociere veloci

The Project

To cope with the problems, Levi gave the volumes a two-geometry design with strong angled sections, thus extracting a compromise capable of good efficiency in glide but able to accommodate the needs of displacement sailing. In terms of the hull, keel and edges went up toward the stern, except for a straight course against the keel, terminating in a stern step at the same height of which two adjustable flaps allowed increased planing thrust.

The keel was then ballasted for sailing needs, with ballast added in seawater to counterbalance heeling. Ballasts that were emptied or filled as needed. The drift, on the other hand, was of the movable type, so that it could be used or retracted depending on the type of navigation. Also to be adapted was the rudder, tapered specifically to reduce friction, especially in planing phases. The minor problem was that given by the surface propellers, yes large, but close to the aft step and therefore of minimal impact on hydrodynamic resistances.

Exocetus Volans – Propulsion and performance

In terms of propulsion, to see the greatest compromise was rigging, with a very small mast and consequent minimal sail area, sufficient, however, to enable the hull to reach satisfactory sailing speeds, as high as 8 knots, with angles to the wind as low as 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.

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. Unfortunately, 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.

Data Sheet

You might also be interested in:

Classic Boat: quando Renato Sonny Levi batté il record di velocità con l’Arcidiavolo