I had promised myself that I woullld not intercede on the dimple tape. But,
I see now that I must. If you reread the original thread on the tape you
will find that the author had some trouble proving the fact that dimple tape
works. I found that amusing because...least drag is found using laminar
boundary layers. Ie smooth air flow from front to back. There was also some
chat about tripping the boundary layer. Here is the real deal...tape added
to the smooth air flow fouls up the boundary layer. So you think, maybe if
the boundary layer is off the car, it will go faster? Nope. Here is what my
aero experience and texts say...." Because of the oscillation of the fluid
particles in the turbulent boundary layer, an interchange of momentum and
energy is possible among the individual layers comprising the the complete
bounday layer. This permits a transfer of energy from the free stream
through the outer portion of the layer to the inner portion, with the
result that the turbulent layer has a fuller velocity profile than a liminar
layer and a steeper gradient at the surface. The greater capicity of the
turbulent boundary layer to remove energy from the fre stream as compared to
the laminar layer not only results in a higher energy level throughout the
turbulent layer, but also increases skin-friction drag,owing to grater
energy loss in the free stream."
If this worked, every race car that is used to race for money would have it
everywhere. The cars themselves would be dimpled every where. As to tripping
the boundary layer, the edge of the tape does that, let alone the "dimples".
The best drag reducing is to have a seamless car, painted with a really good
paint and waxed to death. Smooooothhhhhhhh....
so in my estimation, putting dimples on the bottom of the pan would in fact
slow the air causing a high pressure build up under the car and, well you
get the idea...
Oh, now you want to talk about golf balls...ok, dimples are added to golf
balls for stability. Sorta like the rifling on a gun barrel. Remember a golf
ball can spin up to 10,000 rpm off a high number club and 2500 to 2800 off a
driver. The spinning with the dimples tries to keep the ball flight as
stable as possible. Does not reduce drag to my knowledge, but might because
of the spherical surface...
mayf
> Keith,
> After all our jawing and joking about dimple tape
> last week, your belly pan question got me
> thinking=(DANGER! Danger, Will Robinson!) Do I
> have this backwards or is this a valid theory?
> If the entire belly pan was dimpled, and the top
> of the car was smooth, there would be less drag
> on the belly pan than on the top of the car,
> mimicking the same effect as more air flow under
> the car, resulting in an effect like an upside
> down wing - which would add downforce as speed
> increased. Or did I get that backwards, and the
> car would take off like a frizzbie?
>
> =====
> Dick J
> In East Texas
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