An array of strain measuring FBGs in bare fiber, the FS70FBG, was chosen to carry out the deformation measurements and – for each foil -four measurement points were determined. “The discussions with the customer enabled us to understand all his needs and to propose solutions. The same fibre could be used to carry out the temperature measurements. We therefore agreed to customize it and integrate a thermal sensor into the array,” explains Carola.
According to the customer’s specifications, all these measurement points (Bragg gratings) are determined and precisely placed along the fibre. This fibre is coupled to the FS22 DI dynamic optical measurement system (also known as an optical interrogator), which converts the optical measurements into digital data that can be used by conventional acquisition systems. The distance between the farthest measurement point and the optical interrogator is five meters – a relatively short distance in comparison to some applications that require fibers with a length of more than 30 meters.
A race against time…
These technical choices were defined in the first quarter of 2019. At that time, the race against time was already underway for IMOCA Thomas Ruyant Racing, who wanted to line up their boat for the double-handed Transat Jacques Vabre, scheules to sail from Le Havre to Salvador de Baia in Brazil, on 27thOctober. So – for practical reasons and to save time – the foils were completed in Lorient, rather than Milan, as initially planned. HBK’s engineering teams have expertise throughout Europe, so adapted easily to this change of plan.
As a result, the installation of the optical gauges was carried out by HBK’s Field Service Engineer, Nicolas Visoianu who is based in the companys’ French office.
The foils – comprised of a technical stack featuring several layers of carbon fibers – have been specially designed to integrate with the optical fiber and the outer part contains a groove. Inserting the fiber into this groove is a meticulous job, as explained by explains Nicolas: “As these are relatively heavy and difficult to handle, the foil was fixed in a position that would allow me to work in good conditions. To obtain optimal performance, it is very important to position the fiber precisely and to pay great attention to the bonding. Mistakes made here cannot be corrected! In this area, HBK has acquired expertise that sets it apart from its competitors. In the end, one must be able to supply μm/m, guaranteed with acceptable uncertainty. This is a level of expertise that is difficult to achieve.
The X120 glue used is also an illustration of the expertise in this field – it has been specially designed for mounting this type of gauge. It fills the groove until it is flush with the surface, allowing a protective layer to be added, making it resistant to seawater.
This project was quickly finalized, enabling the boat to launch in September 2019 – eight weeks before the start of the Transat Jacques Vabre. After a few tests, it was lined up for the race. In spite of a failure – linked to the automatic pilot jacks – shortly after the start, which forced a four-hour stopover in Cherbourg, Advens for Cybersecurity proved to be very efficient and finished in an admirable fifth place. This comeback is due to strong averages; in one day alone, the yacht covered 521 miles in 24 hours at an average speed of 22.30 knots.
The foils obviously played an important role in achieving this performance. Thanks to the sensors and the acquisition system, the skipper was able to use them optimally, without exceeding the limits
- Laurent Bourgues.
After this successful first race, an assessment was necessary, so the recorded data was analyzed and correlated to look for ways to improve. The measurements taken on the foils are a valuable source of information to improve the boat’s handling. “The price to pay is consumption: 1 A at 24 V is not negligible,” says Laurent Bourgues.
For Nicolas Visoianu, it is possible to act on this consumption: “This figure includes the optical part, but also all the associated electronics for data processing. It should be considered that this consumption may not be permanent, as foils cannot be used in all wind and sea conditions”.
Advens for Cybersecurity’s CEO, Alexandre Fayeulle, adds: “The Transat Jacques Vabre has confirmed the extraordinary potential of Advens for Cybersecurity. This boat is very well born – you can feel that she is ahead of her time. We are full of hopes and inflated with ambitions for the next VendéeGlobe.”
By then, everyone will be on deck…including HBK!