BMW has proposed a clever solution to prevent water from dripping into the trunk when liftgates or trunk lids are opened in rainy weather. In a patent filing with the European Patent Office, the automaker describes integrating rib-like ridges onto the lid to channel water toward the top of the tailgate, ensuring it stays out of the trunk.
While many automakers design drainage systems to manage water running off rear windows, runoff from the sides of the lid often ends up on the trunk carpet. Poor designs, such as the Tesla Model 3’s small gap, allow water to bypass channels entirely. BMW’s innovation aims to address this common issue, keeping trunks drier and more practical in wet conditions.
Controlling The Water’s Path
When you open a car’s trunk, gravity ensures that the water that’s accumulated on the lid or liftgate takes the path of least resistance. The top of the tailgate is at its lowest part when open, so ideally all the water that runs down should land on the rear window and drain away into the channel behind the raised lip of the trunk opening’s rubber seal. However, it’s inevitable that some water willl spill over the back edge and over the sides.
BMW’s patent describes V-shaped riblets on the trunk lid’s surface to channel water to the sides in a controlled manner. There, it is stopped by a raised ridge along the edge of the lid, channeling it down along the side and to the rear screen. In theory, this should channel all the water on the lid toward the rear window to be drained away, keeping it out of the trunk. These ribs can be either styled into the lid or attached as separate parts.
Balancing Functionality and Style
BMW’s idea is sound in principle, if it can style the riblets into the trunk lid in a way that won’t compromise the car’s styling, else widespread adoption in the fashion-conscious car market seems unlikely. Add-on parts are unlikely to integrate into the design unobtrusively, and ridges designed into the lid pressing might demand style compromises not sufficiently compensated for by the purported functionality.
