Hydroptere
The fastest sailing boat of the world combines dream and high technology. This extraordinary sailing boat can fly over oceans at a very high speed combining the leading techniques of the aeronautical and marine industries.
Hydroptere is a unique and innovative project, which conveys extremely strong human and technological values.
Motivated by passion and daring, Hydroptere teams knew how to take advantage from the technological innovations to make a pioneer boat fly and become reliable, combining glide and perfection.
Hydroptere’s secrets
To understand Hydroptere, a little review session is necessary! First, an etymological review. In Greek, hydros means “water” and ptère means “wing”. And then a mathematical review, with Archimedes’ principle saying “A body immersed in a liquid is buoyed up by a force (buoyant force) equal to the weight of the displaced liquid.” Thanks to this theory elaborated twenty-five centuries ago by a Greek genius, traditional boats can float but with much resistance to achieve high speeds. It was then necessary to make the boat rise above the sea surface to eliminate this drag by replacing Archimedes’ buoyant thrust by the water’s dynamic lift. This physical phenomenon has been analyzed in detail for the air in the early twentieth century by aeronautical engineers and its application to water (800 times denser than air) is one of the prides of the Hydroptère team. To take off, Hydroptere has "marine wings", the foils, which are placed under each of the floats of the trimaran.
Once the boat reaches 10 knots, these immersed “wings”, deployed at 45 degrees in the water, generate an upward thrust. With the appropriate angle of attack of the foil, the sum of the pressure at the intrados and of the depression at the extrados generates an upward thrust with a reduced drag, which raises the boat like the wing of a plane. This is called the “lift” i.e. the same principle that allows the wings to make a plane take off. Then the hull and the floats of Hydroptere fly five meters above the sea surface. Only 2.5 m² of the boat are in contact with the water and she is able to sail from 20 to 45 knots (from 37 to 83 km/h) in 10 seconds. And same result in the sea and in the air, the higher the speed, the greater the lift.
In theory, everything seems to be very simple. But in practice, the achievement of this incredible project has encountered numerous obstacles. Between the initial model made in 1985 and the first record broken by Hydroptere in 2005, Alain Thébault worked hard during twenty years and fell many times before finding the ideal configuration which allows this technological jewel to fly above the water.
But in the end, they managed to combine opposites: Lightness and robustness. Because the foils must resist pressures twice as high as those exerted on the wings of a jet fighter. To do this, they used composite materials such as carbon fibers impregnated with epoxy and associated with titanium parts. To meet the laws of hydrodynamics, the shape of Hydroptere has been optimized to ensure a greater efficiency of the sails while minimizing as much as possible the air friction on the structure of the sailing boat. The “papés”, the brains of the high-tech industry who have been helping Alain from the genesis of the project also equipped the cross beams with huge strain absorbers, inspired by the landing gear of the airliners. They imagined a reversed centreboard, similar to that on the planes and designed absorbers derived from that of the Rafales, which allow the foil to be lifted during a strain peak and then to come back to its original position before the next wave. They also installed on board a hundred sensors which measure the pressures, the twisting or the speed. The data acquired are modelled in a flight simulator to analyze every reaction of the boat and to improve adjustments. They have realized thousands of calculations to reduce the problems of hydrodynamic flow: When Hydroptere reaches 50 knots, the water begins to boil around the foils, which reduces the lift and stability.
Today, thanks to the passion, energy and daring of these worthy successors of Ulysses and Icarus, thanks to the alchemy of science and resourcefulness, marine sensitiveness and cutting-edge technology, Hydroptere is the fastest sailing boat in the world. With the help of, Alain Thébault and his team wish to write a new chapter in this epic between the sky and the sea, with the conquest of the greatest oceanic records.
Dimensions
Length: 18.28 meters (60 ft)
Overall length: 18.28 + 4.5 = 22.78 meters (74,7 ft)
Length of the floats: 6,7 meters (22 ft)
Span: 24 meters (79 ft)
Draft: from 1.5 to 4.5 meters (4 meters = 13 ft)
Height of the crew above water: between 3 to 6 meters (5 meters = 16 ft)
Mast: 28 meters (92 ft)
Length of the foils: 6 meters (19,7 ft)
Weight: 7,5 tons
Sails
Gennaker area: 315 m² (3391 s.f.)
Mainsail area: 185 m² (1991 s.f.)
Maximum sail area in flight: mainsail + gennaker + staysail = 185 + 315 + 60 = 560 m² (6034 s.f.)
Speed
Wind speed required to take off: 12 knots stabilized
Speed of the boat: About twice the wind speed (she sails at 30 knots with 15 knots of established wind)
Maximum speed: 56 knots (= 104 km/h = 65 mi/h)
Maximum average speed: 50.17 knots on one nautical mile (outright speed record = 93 km/h = 58 mi/h)
Team
Crew: from 5 (offshore sailing) to 11crew members (outright sailing speed records)
Architects: VPLP, HDS, Hydroptère team (including Alain de Bergh and Philippe Perrier)
Shipyards: central hull (DCNS Lorient), floats ( shipyard Decision), crossbeams (Airbus Nantes), foils and rudder (shipyard B & B + Airbus Nantes), mast (Lorimat), strain absorbers (Legrand & Revigny), sails (North Sails and Incidences)
Measurement system: HBM
Materials: carbon and titanium
Building cost: priceless (25 years of development)
Other features
- In flight, 2 m² of the boat surface are in contact with water
- Hydroptere accelerates faster than a 2x250 HP speedboat
- Hydroptere is piloted in three dimensions with a joystick that manages the boat ‘s balance
- There are 30 measurement calculation ways on the boat that indicate the strains in real time
- The boat is equipped with an inertial unit from OCTANS
- The strain absorbers on the foils are designed on the principle of the landing gear of aircrafts. They absorb the strain from 32 tons.
- There can be up to 48 tons of strain on the bindings that maintain the crossbeam. The bindings of the mainsheet traveller are designed to withstand 100 tons.
- 10 m² living space in the central hull
Hydroptère
From the Greek hydros (water) and ptère (wing), Hydroptere is a trimaran with foils. These underwater wings extract the boat’s hulls from the water when a certain speed is reached, which considerably reduces the ship’s hydrodynamic drag.
Thus, Hydroptere can attain very high speeds.
Principle
No longer floating on the water, but flying, the ultimate dream. To free oneself of the Archimedes’ principle, the boats’ hulls are lifted out of the water thanks to a vertical thrust given by the foils.
Then the foils are the only parts in contact with the water, which results in a considerably reduced drag and thus gives the opportunity to achieve far higher speeds than traditional boats.
The functioning of the foils is simple and based on the principle of dynamic lift, allowing the wings of a plane to make it take off.
Thus, when it manoeuvres in the water, the foil generates a difference in pressure between the lower and upper surfaces of the wing. This difference in pressure is translated physically by an upward force and applied to the foil, which is called lift. The greater the speed of projection of the foil, the more the lift increases. After a certain speed, the lift generated by the foils becomes superior to the weight of the boat and it causes the boat to be lifted out of the water. The geometry of the foils used on Hydroptere is conceived so as to limit the increase of this lift, so that the boat stops rising and is stabilized a few meters over the surface of the water. The foils used are V Autostable foils.
This very simple concept allows for an easy application, but the stress exerted is such that it was necessary to wait for the advent of new materials such as carbon and titanium in order to be able to make a large-sized boat fly over the waves.
Archimedes’ principle
A body immersed wholly or partially in fluid (liquid or gas) is buoyed up by a force (buoyant force) equal to the weight of the displaced fluid. That force is called “the Archimedes’ Thrust”. In a field of uniform gravity, the thrust of the Archimedes’ PA is always given by the following formula:
where Mf is the mass of the fluid contained in the displaced volume V, and g is the value of gravity.
If the density ρ of the fluid is also uniform, we will have:
or if we consider only the greatness of the force:
The Archimedes’ thrust PA will be expressed in Newton (N) if the density ρ is in kg/m³, the displaced volume of fluid V in m3 and the value of gravity g in N/kg (or m/s²).
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