[OT] Rear Wing Aerodynamics - long

[T Berk <tberk@mindspring.com>]

Case Study:

Toyota Conversion Flatbed Stake Truck.
It had dual wheels on the back, that is; one axle but four tires. Wooden
flat bed that was about ten feet in length and about square. 

We used it to transport containers from the recycling center to the
weigh station, we could fit two boxes made from plywood sheets on the
back plus some fiber barrels, so that gives you some idea of the scale
of things.

The truck had a high front wall or panel that served and a backstop for
strapping things to and made up one of the walls when the other
removable staked sides were put in place. Trouble was it extended up
above the roof of the cab about two or three feet.

One trip we were coming back on the freeway with one large wooden box
(dimensions: one sheet of plywood long, one half sheet deep front to
back. About 8'x4'x4'). Also we had the collapsed shapes from some
cardboard boxes of similar size, these were strapped to each side so
that the box was flush with the backboard of the truck and the cardboard
(being flattened) with one on each side was making a dovetailed shape at
the rear, kind of like a wedge shape with the pointy edge facing aft.

It stuck out past the flat bed a foot or so but the point was we now
could get the little under powered truck to do over 80 mph on the
freeway, big wind catching wall right behind the cab and all.

Super aerodynamic, I have thought about it over the years and conclude
it is not enough to split the wind (Hey, I didn't mean cut the cheese!)
but it's also important to close it up behind you as you pass by.

Hence the needle shape at both ends of really fast things, like the SR71
Blackbird airplane.

So, Scirocco content at last, part of the benefit the rear wing, with
it's sharp edge is to get the flow to combine back again, to avoid too
much turbulence back behind the car as it swirls and creates a vacuum.


TBerk

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