The wing, which is the supporting foil, is mounted on two spars. The angle of the foil is permanently electronically adjusted so that the boat is horizontally stable, moves smoothly in wakes and leans natural while banking. At the wing, which is formed like an airplane wing in cross section, an overpressure develops at the underside, at the upper side a negative pressure.
The thrust of the propeller gives the candela 13 to 14 times more lift than resistance. 100 kg of propeller power will easily make the 1.3 tonne fuselage of the Candela float. With a glider it is only 3-4 kg lift per kilogram of drag, i.e. 300-400 kg.
100 times per second
The big challenge is to calculate the position of the foils (and thus of the hull) accurately and in a flash, so that they keep the boat stable outside the water and the hull does not buckle in turns or waves.
The solution is a state-of-the-art sensor system that calculates all water movements and provides this information to the control of the foils.
Six pairs of sensors permanently calculate the position of the foil © Kerstin Zillmer
Two ultrasonic sensors measure the height of the wave at the bow, accelerometric sensors the acceleration, gyro sensors measure the heel, a GPS the speed, hygrometer the height differences. All data is evaluated with a self-developed software. Mathematically it is determined where the boat is located in space, at what angle it does this, with what acceleration and what speed at how much wave.
Service management via the cloud
This flood of data is recalculated 100 times per second. In this way, the software can permanently predict how the boat will behave in the next moment under the given conditions, as known from space technology.
The position of the wings is also calculated 100 times per second. Of course there was no ready-made software for this technique, it had to be written first. The printed circuit boards are also manufactured in-house at Candela. For service management, the boat is connected to a cloud, data download is also possible.
Heckfoil mit Getriebe © Kerstin Zillmer
Candela PCBs © Kerstin Zillmer
The mechanics make the difference
But there is more innovative technology in the candela: It is essential how the data is forwarded to the respective foil and how the foil is then directed. Together with his experts, Hasselskog has developed a mechanical wing connection that works as a coupling between the spars and the wing. This was very complicated to construct because the joints had to be able to move permanently in all directions.
The next big challenge was the drive unit. For the optimal hydrodynamic design, the correct weight had to be calculated in proportion to the drive and the wing. The transmission had to be very small to make the whole drive lighter and more efficient. The team managed to develop a gearbox with an extremely small diameter of only 83 mm to keep the drag as low as possible.
The extended shaft with the self-developed motor housing © Candela
Since the shaft to which the rear foil is attached must be longer than a conventional electric outboard, Hasselskog and his crew also had to develop the engine casing and the shaft itself. The shaft with the mounted T- wing must be as flexible as the front wing. The right angle of inclination is essential to lift the boat out of the water.