Success story: “Hai-Light” – BASF SharkSkin tested with ACCRETECH HANDYSURF+

“Hai-Light” – tested with ACCRETECH HANDYSURF+: Advanced shark skin film from BASF Coatings on aircraft reduces CO2 emissions

A film, modelled on the skin of a shark, now reduces air resistance and thus the emissions of climate-damaging carbon dioxide in aircraft. Münster-based film and coatings specialist BASF Coatings has developed a high-tech film that has now been used on 25 Boeing 777 and 747 aircraft since 2022. BASF Coatings checks the condition of the “NovaFlex SharkSkin” glued to the hulls of the aircraft using ACCRETECH’s portable surface measuring device called HANDYSURF+.

Sharks are among the fastest swimmers of all. The cartilaginous fish can reach up to 70 km/h under water. This is made possible, among other things, by the nature of their skin, which consists of scales with a ribbed structure, reducing flow resistance.

The stylus of a RONDCOM is measuring the roundness of a ball as a reference standard.

The insight is not new. But transferring it to aircraft is a real innovation. BASF Coatings spent five to six years developing the SharkSkin, reducing drag, saving fuel and hence CO2 emissions. Tests in wind tunnels, computer simulations and tests around the fuselage of the aircraft models in question provided in-depth insights into aerodynamics and flow conditions as well as the requirements for the SharkSkin and its orientation on the aircraft. The result is a self-adhesive film that has a rib or “riblet” structure. The riblets measure about as much in height as the diameter of a human hair. Hardly visible to the naked eye, but noticeable with a fingernail. In principle, riblets can be used wherever turbulent flows prevail. For example, on trains, ships, automobiles, wind turbines, etc. Thanks to the new product, the Coatings division was able to secure the BASF Innovation Award 2024.

During production in Münster, the riblets are applied to a carrier film. On the upper side, another layer protects the structure and on the underside, an adhesive film prepares the SharkSkin for use on the aircraft. Around 800 square meters are needed to foil an entire hull. When gluing the aircraft, the workers have to meticulously adhere to the pattern before cutting the patches, which are about half a metre in size, and carefully gluing them to the fuselage of the machines using a rubber squeegee. This is because the inflow angles are not the same everywhere. A patch attached at the wrong angle, for example, could increase consumption instead of reducing it.

The result is impressive: To date, a total of 25 Boeing 777 and 747 aircraft have been equipped in scheduled and cargo service with the SharkSkin, saving around one percent of kerosene. On a transatlantic flight between Germany and the USA, for example, 1.5 tons less fuel flows through the engines. This reduces the emission of the climate killer CO₂ by an impressive 4.7 tons on just one flight. The 12 SWISS Boeing 777s alone are able to save 15,000 tonnes of kerosene annually with the “skin”, calculates Patrick Scherrer, project manager at SWISS. This corresponds to a quantum that would be needed for 87 flights between Zurich and Mumbai in India.

During operation, the film is exposed to extreme stresses. The SharkSkin not only has to withstand dust, sand, water and de-icing agent, but also intense UV radiation which can potentially harm the film. The deformation of the fuselage during flight operations also means the skin requires sufficient flexibility. In addition, the film must withstand the high temperature differences between the ground and the flight altitude. For example, the take-off takes place in a desert state at 50 degrees Celsius, and at cruising altitude, the hull is exposed to temperatures of around -60 degrees Celsius – and that at around 900 km/h.

Here you see the external view of the headquarter of eumetron.

Since the film interferes with the aerodynamics of the aircraft, the durability of the SharkSkin had to be proven in tests in order to obtain approval for use on Boeing models. The aim is now to release it for other aircraft types and to use the foil on the wings. This will mean another quantum leap and raise the savings potential of the SharkSkin to the level of “winglets” – those vertical processes at the end of most commercial aircraft wings. The winglets reduce consumption and emissions by a good three percent.

The film on the machines must be regularly checked for damage and wear, and it is not possible to check the condition of the riblets with the naked eye. On top of that, such an inspection always poses a challenge in that it must be able to take place at all points of the aircraft fuselage – even vertically or overhead. Bulky and heavy measuring devices are therefore ruled out from the outset. That’s why BASF Coatings relies on the reliable, accurate and universally applicable HANDYSURF+ surface measuring device from the renowned measuring equipment specialist ACCRETECH. BASF has been successfully using the compact, portable device since 2020.

Marc Daniel from the Technical Development Aviation department at BASF Coatings is convinced by the HANDYSURF+. “The device is ready for use anytime and anywhere, very easy to use and measures extremely accurately,” says the technician. In the specific area of application, roughness measurement is used as a measure of the quality of the riblets.

The HANDYSURF+ has a measurement range of 370 μm on the Z-axis – the largest in its class – and achieves a resolution of 0.0007 μm across the entire measurement range. Software called “SupportWare_II” is also included, making data outputting and detailed measurement reports possible. The user can choose between 2μm and 5μm probes. ACCRETECH also supplies the device with a roughness standard including two measuring surfaces, and including a calibration certificate, as well as a compact carry case.

BASF Coatings also uses the optional ACCTee software, which allows measurement points to be read and analyzed quickly and easily – with a module for roughness evaluation and another for measuring contours.

In a test run with devices from different suppliers, the ACCRETECH HANDYSURF+ turned out to be the best for the purpose. And on top of that, the device is also used in the quality assurance of SharkSkin production. So the HANDYSURF+ turns out to be an all-purpose weapon around the high-tech film. And ACCRETECH is thus making a contribution to climate protection and a more sustainable future.

Contact:

ACCRETECH SBS UK Ltd.
Tim Wood
Head of Industrial Metrology
Unit 2, Leofric Court Progress Way
CV3 2NT Coventry
Phone +44 (0) 2476 651 774

More about HANDYSURF+

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