Project Sipster part 8: All the Drag-Reducing Details


Aero Protrusion Patrol

'70s cars are riddled with lumps, bumps, warts and protrusions (yes, it's a 1981 Rabbit, but it's still very much a '70s design). The marker lights on the rear fenders, for example, stick out almost an inch. We removed them and taped over the hole. 
The mirrors are dead flat, like little air brakes. There's no law requiring a passenger's side mirror, so we removed ours. And there's no law requiring you to aim your mirrors properly, so we folded the driver's side mirror flush against the body and just turned our heads more when we drove.
The rain gutters on the A-pillar are deeply offensive to airflow, but also quite tricky to remove. The gutter isn't just there for rain, it's the seam where the roof panel is welded to the sides of the car. We planned to cut it off, a few inches at a time, weld up the resulting gap, grind the weld flat, smooth it out with bondo, sand it, primer it, and paint it to match the car. Does that seriously sound like something we could pull off? We hit the gutter with a hammer until it was as flush as possible, then smeared some silicone around to smooth over the bump. Good enough is just right.
Project Sipster Aero Mods

Finally, the windshield wipers. Modern cars hide their wipers under the trailing edge of the hood. Ours just sat out there in the airflow mocking us. To minimize their impact, we removed the driver's side wiper and reset the wiper mechanism so the passenger's wiper stands straight up when parked and wipes enough of the driver's side to keep us from running over too many children. 


Aero Body Kit
The Volkswagen Cabriolet used the Rabbit's shell well into the aero-conscious '80s, so Volkswagen saw fit to equip it with a body kit, consisting of smooth bumper covers, fender flares and side skirts that discourage air from slipping under the car and kick the air out around the tires. We used it to questionable effect.

Project Sipster Aero Mods

Project Sipster Aero Mods

Here you see John McNulty, an actual UCLA Aerodynamics professor, trying to make our car more aerodynamic by sticking parts of some sorority girl's old car to it. 



Aero Rear Wheel Covers
Keeping the wheels hidden from the airflow worked on the original Honda Insight, not to mention Boss Hogg's Eldorado, so we fashioned wheel covers from Coroplast and screwed them to a steel support bar that was welded to a screen door hinge for easy tire changes.  

Project Sipster Aero Mods


This worked great in my mind, but in reality, the bottom of the Coroplast hung much farther away from the body than I anticipated, past even the Cabriolet body kit. Desperate for something to gently push air off the body and out to the wheel covers, we finally duct taped rusty paint roller tins in front of the rear wheels.
Now, About That $7,000 Part…
Claiming that a car as quick, economical and downright charming as the Sipster cost less than $7,000 has some people baffled. The cries of incredulity were many. What about labor costs? It's called doing things yourself, kids. We did lots of this work ourselves, and whatever work we farmed out, we only did because of our arbitrary and ridiculous deadlines. Properly motivated, you CAN do this on budget.
Without labor costs, the accounting is simply a matter of adding up prices for everything necessary to hit the project's goals. So in parts only, our Sipster's triple-7 performance could be reproduced for $6993.21. Don't believe it? If not, then reading the chart below probably won't help.



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