Best spoiler orientation: Vertical vs horizontal?

Wondering if anyone has compared the benefits of a horizontal vs vertical oriented spoiler on a car? While the horizontal is by far the most common, my guess, the vertical orientation would deliver the best aerodynamics and reduced drag. Click on tiny icon below to see photo of vertical orientation.

The Tatra has a “fin” or vertical stabilizer, not a spoiler

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Ok, semantic point taken, but is the vertical fin better or not as good than the horizontal spoiler for aerodynamic and mpg purposes?

In todays day and age of getting the best MPG, MPG, MPG, save the world, gas is killing us all etc etc, needing to be the absolute best MPG it can be, how many cars do you see with fins now a days??? That answer should answer your question… :wink:

And a vertical spoiler would be the same as pushing a billboard down the road, about the least aerodynamic you could get… lol

two separate things and used for different reasons basically, think of an airplanes wings and tail fin…

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Then there was the 57 Plymouth with two vertical stabilizers. I thought it ‘was just to make it look like a rocket.

Interestingly, sounds like Porsche stole some of the design and vw finally paid them off.

Basically yes, just styling cues…
That was in the space age era and used on vehicles to make them look more space age…

That Tatra had wicked oversteer. The claim is Tatra’s killed more Nazi officers than the allies. The officers were banned from driving them after more than a few were killed. The fin was to mitigate it a bit. Didn’t really work but…

Spoilers go across the car and are attached to the car… front or rear. Drag tends to really increase at angles of 45 degrees or so although front spoilers can be vertical. Wings are upside down airplane-types mounted front, rear or mid that are far more efficient in producing downforce than a spoiler. Their angles of attack tend to be below roughly 30 degrees from horizontal and can have several planes.

None tend to decrease drag unless they are basically Gurney flaps, or very small spoilers. Spoilers and wings are designed for downforce at the expense of drag.

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Fin only affects directional stability, no benefit for mpgs or road holding.

One of the car magazines in 1959 or ‘60 ran an article tititled Fins, function or fashion.
American auto makers also argued their case for who was first.
To add to George’s confusion, the 1959 Chevy had horizontal “fins”, more like wings, rather than stabilizer or fin. Allegedly they actually provided some lift, reducing rear end stability.

I think what George is trying to say is the difference between a wing and a rear deck spoiler - and the answer is that spoilers are there to help generate downforce, but they do have the effect of reducing drag, but wings generate downforce without excessive additional drag, so they are more efficient, which is why if the rules allow, you’ll find race cars with wings rather than spoilers.

But for the best MPG, you want the body designed so it doesn’t need a spoiler.

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Or an absurd looking “fin”.

Personally, on a regular passenger type car, I think the best spoiler orientation is…none at all.

I see some ridiculous spoilers around my part of the world, on both Asian-type “enhanced” cars, and on pickup truck beds. All may be “functional” in some way, but I suspect it’s more for ego-maintenance than actual aerodynamic function.

But I’m no scientist, so what do I know.

You would think that someone who watches so many vehicle TV shows and reads lots of car magazines would know that Spoilers are never vertical.

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Combine the two, get yourself a Plymouth Superbird or a Dodge Daytona.


The late, great Virgil Exner was fond of calling tail fins “vertical stabilizers”.

The Superbird and Daytona were not popular when they were new. That’s one of the reasons why they are so expensive now. I’m still unimpressed with the looks. I realize that they were built for NASCAR and sold to regular customers to meet NASCAR requirements. IMO they took a good looking Charger/Road Runner and ruined it with that aero nose and huge tail.

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image

:smirk:

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I’m watching the IMSA race at Laguna Seca. The GTP cars all have horizontal and vertical stabilizers. These advanced racers wouldn’t use them if they weren’t useful.

Once again, a spoiler does NOT create downforce, it reduces lift. A wing creates downforce (as used on cars). Vertical stabilizers are only effective at very high speeds, like at Bonneville.

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Vertical stabilizers down the center improve yaw stability… at racing speed. The endplates, the vertical plates at the sides of the wings, improve the wing’s downforce and reduces drag.

IMSA GTP cars, Indycars and F1 cars all use these parts.

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