So after riding in the cold all winter (yea, I'm a pppsssyyycchho) I finally decided (now that winter just about over) to get myself a new, bigger windshield. I started with this unit. I mounted high up and at an angle and it gave pretty good protection around the chest and neck area, although the face, hands and arms had no protection. The new shield was this unit. It looked nice on the bike and I was pleased with the construction and installation. But, 2 minutes on the road and I hated it. The problem was that there was alot of turbulance off the top edge which hit square on the helmet. The noice was unbearable. Visibility was also much worse. There was also an area on my upper back which started to feel the wind as it curled around me. Now I'm no expert on aerodynamics (but I do understand some basic stuff) and here's my theory as to why the small shield worked so well: air flowing over the small shield was able to get around the bottom as well as over the top surfaces (since the shield is mounted at an angle). The result is an airfoil which deflects the air without causing a separation bubble behind the shield. The larger shield did not allow air under it (as it somewhat sealed itself around the headlamp). The result is a big region of low pressure which cause the air to swirl around, creating the buffetting.
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