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Old 02-24-2014, 12:05 AM   #1 (permalink)
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Beetle aerodynamics (full-scale streamlining mockup of original Beetle)

The reason I focus on the Beetle body is that I think that the area between the windshield and the C-pillar is optimal (excluding the external drip-rails, too fast roofline and non-flushed door windows). It's two occupants wide and plan taper starts at the B-pillar, not the rear axle. Taper in plan meets before the Template line gets anywhere nearly done, so I use a Tropfenwagen tail.

Having looked at the situation with a 3D modeling program, I decided that it was time to 'get real' and see what I could learn. This experiment probably is complete; any further development would be two separate pieces—the front ending at the windshield and the rear beginning with an arc across the roof to the drip-rails. The idea was to leave the fenders and drivetrain undefined for now.

I used 16ft long strips of redwood benderboard to find streamlines from the stagnation point to the tail. They touch at three points—the nose, the roof and the tail, and being knot-free they settle into the smoothest curve. I notice that if the line is pushed sideways the strip wants to twist. It is attached at fender mounting bolts (2 front, 4 rear), side trim holes in front, and with clamps at the lower rear. The rope was a convenience at first and is unnecessary now. It's held together with pop-rivets, 1/2" staples and soft wire. The U-shaped bar at the front is the inner bumper reinforcement from a Type III.

The tail is extrapolated from the earlier experiments with the Superbeetle. The added length is reverse cambered. The first bulkhead is at the position of the earlier 45° tail. The second bulkhead is at the location of the stock rear bumper. It's not an optimal, precise shape. It's asymmetrical and barely held together. The 2nd bulkhead is trapezoidal and the tail leans to one side because I let the materials dictate instead of trying to force it. It goes from reverse cambered at the bottom to not at the top. If the rear wheels were moved out and back, the lower line could be extended to the front of the rear wheel-well without much change at all.

This could be done with no fenders, stock fenders, or VLC style pontoon fenders. With an electric drivetrain, the lower rear could be raised quite a bit. If the top of the rear was raised, a V-shaped backlight could be added.

At this point I'l probably go back to the Superbeetle. I had an 'a-ha' moment on that the other day. ...and it's drivable.

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