The McLaren Spider's windshield is a deflector, not a lid. Its steeply raked glass guides oncoming air upward, reducing direct wind on the occupants while preserving the open cockpit. The distinction matters. Once the roof is gone, air can enter from above and around the sides, where sculpted bodywork and the windshield frame also shape its path.
The apparent shelter behind the glass is less peaceful than it looks. As air passes the upper edge, it forms a shear layer between the faster stream outside and slower air in the cockpit. That layer can become unstable, shedding eddies into a wake where the average pressure is lower than in the surrounding flow. Low pressure is not calm. Differences in pressure help draw air back toward the sheltered region, setting up recirculation that can make the cabin gusty rather than still.
Comfort depends on controlling that wake, not simply making the screen taller. Vehicle speed, windshield angle, side-window position and occupant height all affect how the flow reaches the cabin; a wind deflector can also alter recirculation behind the seats. The result is a tradeoff. A screen that sends the main stream over a driver's head may still leave fluctuating pressure and buffeting inside, accompanied by noise. In an open car, the invisible roof is always in motion.
