Ribbed coatings reduce drag in aircraft
Riblets are longitudinal parallel grooves. The ability of riblets in coatings to channel air flow and thus reduce drag on treated surfaces is of particular interest to the aerospace industry. EU-funded scientists working on the project MISPA, developed technology for a moving coating applicator. It consists of a silicone belt between two rollers that lays the paint belt partially on the surface for treatment. A UV light source cures the painted surface as the belt moves along, leaving a riblet structure behind. Researchers focussed on three key technical issues with the prototype — stable embossing silicone belt movement, controlled paint application and cleaning. A new system prevents the belt from moving steadily to one side of the rollers as this behaviour required periodic manual correction. Paint application was plagued by inadequate control of flow and application. Novel technology prevents accumulation on the inside of the applicator and reduces the risk of excess paint falling onto the surface being treated. Finally, scientists developed an approach to prevent cured paint from sticking to the embossing belt when the applicator crosses an opening in the surface being coated. Following successful tests of each of the three new systems, the prototype applicator was modified to include all three sub-systems in an advanced applicator. MISPA has overcome some of the major barriers to implementation of automated riblet application on extended aircraft surfaces. Future tests of the advanced applicator should pave the way for commercialisation with important reductions in fuel consumption and emissions for the aeronautical industry.
