The Big Thin Fluid

beachflyinbvYou can’t see the air–you can only see what it does. You can see it move sand, create waves, even lift leaves from the ground occasionally. But you can feel it. Hold your hand out the window of your car and feel the force of textured air at 50 miles an hour. Stand on a mountain top in winter and feel the air flow by, milk-thick and smooth.

The air is a big thin fluid, busily rushing around conforming to the shape of its container. The physics is clear, but its complexities are thoroughly unknowable. Fluid dynamics is the realm of high math–the greatest of the wave theorists claim that the math runs out to seven integrals really quickly. Nobody can keep up with that…

Flying hang gliders is all about balance. Suspended below the wing, pilots simply move fore and aft, and side to side, shifting their weight, balancing the wing in the air. To launch, your wings must be balanced in that invisible fluid or you’ll take off into an unwanted turn. But here’s the deal: balance and symmetry are decidedly NOT the same thing. More often than not, balanced wings will not appear level. In order to soar small dunes, you’ve got to stay very close to the hill, deliberately launching into a turn to stay in the lift–a move that will most likely get you banished from a mountain site where you’re trained to fly away from the hill because the area of lift is large and you don’t want to risk hitting the hill in an immediate turn.

You have to visualize the air, feeling it as it crosses your face and wings. Airfow–unseen fluid dynamics. If we could really see it we’d probably never fly in it. At its most basic level, flying hang gliders is learning to stay suspended in the invisible fluid, constantly balancing in the vagueries of unknowable fluid dynamics, never mistaking symmetry for balance.

No wonder it has captiviated my imagination for so long.


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