Solid Sails: our sails of tomorrow?
Oil is no longer the future and the ships of tomorrow may take old routes to be propelled in part by the wind. Chantiers de l’Atlantique markets a solution that we tested in J80!
RIGID SAILS, maybe it’s a bit like round arcs. At the start, the sailor with narrow ideas like the prow of his boat twists his nose in front of so much disgrace and cries out against heresy by brandishing the table of nautical laws (“you will draw pointed prows”, “you will make sails in tissue “). Then he admits that it may not be so ugly (the shapes, he likes that!) and above all that it works well.
Without identifying myself with this type of character (purely fictitious of course), I was half convinced to board the J/80 equipped with a Solid Sail, a concept of rigid sail with composite panels developed by the Shipyards of the Atlantic located in Saint-Nazaire, specializing in the manufacture of ocean liners, warships and offshore structures. Developed for the merchant ship market, in the same way as VPLP’s Oceanwings (a self-supporting wing that raises and lowers fully automatically), the Solid Sail is not intended to equip pleasure boats… Although ?
Our J/80 doesn’t even have ten knots of wind to prove herself with her astonishing mainsail which gives her a little junk air. As a bonus, we are five journalists gathered around Jean Le Cam, which does not make us the lightest crew! Under the eye of the 1/5 scale demonstrator which sits on the dyke of the port of Pornichet (a balestron equipped with a mainsail but also with a jib with panels), we tack without difficulty. Leech telltales help us find the right setting. But that’s the only visual indication we have.
For the rest, the Solid Sail is silent: you just see it widening or flattening depending on the pressure exerted by the wind on the panels. And it’s also very comfortable, this silence: the tacks and gybes are no longer punctuated by the clicks of the faseying and the boom no longer squirms. The sail easily recovers its shape crossing the bed of the wind, even when it is timid.
FROM SHIP TO MERCHANT NAVY
We have no point of comparison but our J/80 is progressing quite well. Jean Le Cam, who tested on board Hubert the upper part of the Solid Sail intended for the Ponant liner, also admits that he was amazed: “The mainsail weighed 700 kg at the time, it’s monstrous!
Depending on the pace, we achieved 80 to 95% of the boat’s performance with a classic IMOCA sail, which is nevertheless very efficient”. Chantiers de l’Atlantique, who contacted the skipper about five years ago, were looking for a boat large enough to be close to reality and to validate all the mechanical folding systems.
Offshore racing and the merchant navy have one thing in common: the systems must be robust and easily repairable. Nicolas Abiven, engineer and friend of Jean Le Cam, is delighted with this collaboration: “Jean does not have his tongue in his pocket, even less when he is not in the presence of the press. He does not hesitate, with his own sense of the formula, to tell us when we are on the wrong track! » Many attachment systems have been tested, including bronze ball joints with stainless steel hoops machined in the mass: « I still have some at home as a souvenir! laughs John.
It was the latter who suggested installing textile attachments directly inspired by the solutions used in offshore racing: Dyneema loops along the leech and “synchronization boxes”, whose attachments work a bit like cruciate ligaments , which coordinate the folding between the front and rear parts of the sail. After working on the joints, the design office tackled the weight gain: the first mainsail of the J/80 weighed 100 kg against 30 today (it’s the V2 that we discover here)!
VARIABLE FLEXIBILITY BATTENS
And even if the Solid Sail remains heavier than a woven sail, the rig does not need to be oversampled because the forces are not transmitted to it but pass internally, in the battens. The engineers are currently working on the volume of the wing by playing on the inertia of the slats.
Their flex is more important at the front (the composite is less rigid), which allows the sail to hollow out. Each panel is in fact composed of a frame (PVC-carbon-epoxy sandwich) and a thin membrane (monolithic fiberglass-polyester) which extends beyond the rear vertical slat to create a drop ring.
The sandwich does not have a mechanical role but makes it possible to get rid of a mold during manufacture (the fabrics are draped directly on the foam). Eventually, the epoxy should be replaced by biosourced resins, at least for the membrane. Because it is really about ecology and savings.
The Solid Sail can be integrated into an existing vessel, preferably carrying passengers and cargo as the center of gravity must be low enough. Within three years, the Chantiers de l’Atlantique aim to build their own boat, the Silenseas, equipped with 4,500 m2 of canvas spread over three Solid Sail rigs. If the liner is theoretically able to sail 100% under sail, it should actually be driven by the force of the wind half the time of the crossing, i.e. a saving of 50% on propulsion.
The rig is controlled by a computer program which offers automated sequences to facilitate maneuvers: hoisting, lowering, feathering of the sail in the wind bed in the event of strong winds (the maximum tolerated list is 3°), inclination of the mast-balestron assembly to be able to pass under a bridge, demonstration in support with the rigging scale 1 installed on the site of the Shipyards…
But while waiting for specific training to be put in place within Merchant Navy schools, shipowners who adopt Solid Sail will have to find the rare pearl, that is to say a sailor with navigation skills, capable of taking the controls in “manual mode” put the boat in safety in the event of a system failure… or quite simply check that the data communicated by the interface (force and direction of the wind, for example) are consistent with the observations.
For us, humble boaters, the limits of the system are not the same. Rather, it is the minimum unit size that raises the question. Only yachts or large catamarans from 50 to 80 feet are concerned, with enormous advantages at stake: durability of the sails and extremely simplified launching and lowering maneuvers (reefing is currently not possible).
We were able to check this last point after our short but very instructive outing: we release the halyard and presto!, the mainsail folds like an accordion. And Nicolas Abiven remarked that the Solid Sail is “the best gift you can give to a gentleman who yells at his wife every time the mainsail is lowered. “In reality…