Our endplates were created to maximize the L/D ratio of the NineLivesRacing wing. By incorporating both a rear cutout and louvers, we are able to reduce the size of the wingtip vortices, while strengthening the underwing vortices. When the underwing vortex is strengthened, it yields more downforce for each point of drag. When you reduce the size of the wingtip vortex, the induced drag is also reduced. Bleeding off some of the high pressure above the wing reduces the pressure gradient slightly, resulting in slightly less top downforce. However, by utilizing the rear cutout, the low pressure under the wing is allowed to mix with the ambient pressure outside of the endplate, which pulls the ambient air with more force towards the underside of the wing, increasing velocity underneath the wing. The rear cutout also produces a weak counter-rotating vortex that weakens the wingtip vortex, reducing induced drag. Combining the two designs allows an increase in the L/D ratio by decreasing the induced drag created by the wingtip vortices. Our endplates are constructed from 1/8″ 6061 aluminum and are currently only offered in raw finish. Endplates are currently made to order.
These results were posted by JMR Analytical on their blog
You can see that using the louvers by themselves actually reduces the efficiency. That is why we combine them with the rear cutout.
Flow and vortex formation of just a cutout
Louvers with cutout and additional slats below the wing