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Proposal for the Development of an Applicator for Microstructured Paint Coatings Resulting in Significant Drag Reduction of Treated Surfaces

European Union
Complete with results
Geo-spatial type
Total project cost
€252 874
EU Contribution
€182 608
Project Acronym
STRIA Roadmaps
Vehicle design and manufacturing (VDM)
Transport mode
Airborne icon
Transport policies
Societal/Economic issues,
Environmental/Emissions aspects
Transport sectors
Passenger transport,
Freight transport


Call for proposal
Link to CORDIS

In the scope of the proposed activity, a device for automated application of a riblet structure based on an existing prototype was to be developed and optimised. The applicator consists basically of a closed silicone belt with a micro structured outer side which imprints a UV-curing paint layer. The belt is led by a number of rollers two of which lay it partially onto the surface to be coated. In between a UV light source cures the paint so that the moving applicator leaves a riblet structure behind.

A riblet structure refers to longitudinal parallel grooves. By arranging this structure with its grooves in the direction of an oncoming flow on a body’s surface, the drag experienced by this body is reduced compared to a non-treated condition. For aircrafts, a reduction in drag means direct savings in fuel consumption and thus a lower impact on the environment as well as cost savings for the operator.

The proposal presented the task of designing and building the improved riblet application prototype for use on a robot-system. For this task, all available information on knowledge gained with the existing prototype was evaluated and supplemented with additional components. Main newly implemented tasks were the incorporation of suitable guiding measures for both the belt and the applicator along with dedicated sensors for guidance control and quality check of the riblet structure.

After the improved applicator is built a work package was dedicated to several robot-trials after which the applicator design undergoes an optimisation based on the trial results. In the end, together with a robot, the applicator applied a riblet structure on large scale components enabling it to be used on an industrial level.


Parent Programmes
Institution Type
Public institution
Institution Name
European Commission
Type of funding
Public (EU)
Specific funding programme
JTI-CS - Joint Technology Initiatives - Clean Sky
Other Programme
JTI-CS-2010-1-SFWA-01-005 Support of development of riblet-application device


Executive summary:

As subject of extensive research riblet structures have been investigated in the past in terms of achievable efficiency, best geometries, materials and basic application techniques. Based on that, applicators for limited scale applications under laboratory or other controlled environments were successfully developed thus extending the usability of the riblet technology towards plane or slightly curved structures with limited sizes.

As promising technology for reduction in aircraft fuel consumption the existing limitations in the available riblet applicator designs were to be identified with a subsequent proposal of several designs for subsystems addressing each topic. With this, the previously intended content of the MISPA project shifted slightly towards more basic development rather than heading straight for an all new applicator. For without the identified basic subsystems performing reliably it would be of no use to create the next generation of applicator.

The three subjects identified for further development were:

  • active guiding of the embossing belt;
  • paint application to the embossing belt;
  • cleaning of the embossing belt.

A system for active guiding of the embossing belt was found to be necessary as the silicone belt tended to constantly move towards one side of the rollers around which the endless belt is driven inside the applicator if left running freely. Without it only short distances could be supplied with riblets before the belt position had to be corrected manually.

Paint application to the embossing belt had already been addressed by using a slotted tube across the belt. It was found that it was not sufficiently possible with this system to control the flow and placement of paint on the belt. As a result excess paint started to contaminate the inside of the applicator with the risk of ultimately also dropping onto the surface to which a riblet structure should be applied.

Clearly the process of applying riblet structures onto the desired surface would have to be an utterly stable process before being used on actual aircrafts. However former investigations had shown that when the applicator crossed an opening in the surface the cured paint would remain stuck to the embossing belt. Without removing these residues from the embossing belt before paint was applied again the continuing riblet track would be disturbed.

For all three aspects mentioned above several possible approaches were identified, weighted against each other and ultimately the most promising one was developed into a test system. Each test system was then examined on its own.

Very promising results were obtained for each individual subsystem such that they underwent another further development in order to be incorporated into the advanced applicator. For this an existing applicator was used as basis to which the subsystems were adapted. In the end the applicator is capable of using all three subsystems simultaneously. A future test phase is thus possible.

In socioeconomic terms the work performed under the MISPA project has led to the solution of some essential impediments of using the technology of riblet application on an automated level. Based on the results obtained during the project the basis has been laid on which progress is possible that will yield a system that is capable of applying riblet structures on extended aircraft surfaces. The resulting reduction in fuel consumption is then not only a significant monetary advantage but also an appreciable factor in protecting the environment by considerably cutting down on the production and release of carbon dioxide and other chemical compounds.


Lead Organisation
Optoprecision Gmbh
AUF DER HOEHE 15, 28357 BREMEN, Germany
Organisation website
EU Contribution
€182 608
Partner Organisations
EU Contribution


Technology Theme
Aircraft design and manufacturing
Laminar flow aircraft coatings
Development phase
Demonstration/prototyping/Pilot Production

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