Quote:
Originally Posted by NeilBlanchard
I have been contemplating taking CarBEN to a wind tunnel. I know I would have to put the back doors on it, and open up the slot exhaust vents on the back, and fasten in the windshield. Oh, and I have to fit the rear wheel skirts at least.
Do I need to fiberglass the whole outside?
Where is the nearest wind tunnel that can test a full size car?
|
So you've decided against coating it with wood glue?
Glassing and making it smooth would be the best. If you don't have it as close to the finished surface as you can, the data from a wind tunnel test wouldn't be very useful.
Parts of the wing surface on the Voyager plane that flew around the world non-stop had a satin or matte finish. They calculated that the weight of filler and paint required to make those areas slick would more than offset the efficiency gain from the drag reduction. But Rutan had a bunch of people learned in the ways of airflow, and access to tools (and money) that folks like us don't. Yet all that didn't make any of the team smart enough to do a ground and taxi test with a full fuel load prior to the day of takeoff on the trip. So the wingtips ended up dragging and ground off enough of the composite and foam until the winglets fell off. Oops. Should've had little wheels or HDPE skids at the wingtips.
If you have the $$$ for multiple wind tunnel runs you could try different surface finishes to see the effect (if any) each has. But for practical purposes at common and legal road speeds for earthbound vehicles, you can't go wrong with making the surface as smooth as you can.
Or call up Scaled Composites and see if they'd be interested in having a look at your car.