frontal area vs cd

[Peter Hill]

Originally Posted by samwichse

Pretty much this. Go buy an Insight with a blown engine/crapped out CVT and a dead hybrid battery. Stick your electric bits in. Go.

But you can do it with so much more style by getting a RX-7 FD and they blow engines daily. Also gives more flexibility in transmission.

Cooling system is responsible for 5-10% of vehicle drag. Rule of thumb, input energy is equally split between wheels, exhaust and coolant. As you will be blanking off a 250bhp cooling system instead of 67bhp it will be near to 10% of total drag while the Honda will be around 5%.

RX-7 FD (base) 90% of 0.518 = 0.466 m².
Honda Insight 95% of 0.474 = 0.45 m².

Not cashed in rear wheel spats or disc wheels.

Is it worth it when you will be seen in a Honda Insight?

Originally Posted by renault_megane_dci

I'm interested in that question too but more thinking along the lines of :

Would it be plain stupid to add a perfectly shaped roof addition in order to get a better angle at the back ?

Thanks in advance.

A slant back is nearly as bad as a notch back. All modern hatchbacks although fully conforming to the definition of a Kamm tail have a spoiler that extends the roof line a long way past the hatch to make a recessed transom that is required for a Camm tail.

[samwichse]

Originally Posted by Peter Hill

Not cashed in rear wheel spats or disc wheels.

Is it worth it when you will be seen in a Honda Insight?

Yes, because I want to be seen in a Honda Insight.

Also: The Insight is all aluminum/plastic. Rust isn't much of an issue with these cars (aside from some fittings). Can you say that about an RX-7?

[Frank Lee]

I'd like to be seen in an Insight too. I don't drive enough to make updating my fleet worth it though.

I know that I feel like a douche when riding in SUVs.

[renault_megane_dci]

Originally Posted by Peter Hill

A slant back is nearly as bad as a notch back. All modern hatchbacks although fully conforming to the definition of a Kamm tail have a spoiler that extends the roof line a long way past the hatch to make a recessed transom that is required for a Camm tail.

I need to draw a sketch ...

[aerohead]

Ideally,the spoiler would also incorporate the sides such that the aft-body is literally chopped off like a loaf of bread

[freebeard]

Originally Posted by renault_megane_dci

Would it be plain stupid to add a perfectly shaped roof addition in order to get a better angle at the back ?

No, it would not. Replace the square windshield header with a half-circular one and work your way back from there.

AKA bubble-top coupe.

[aerohead]

Originally Posted by Xist

There is not much on-line about the Monoposto, in English, at least.

In 1958,Mercedes-Benz used this word to describe any open-wheeled Gran Prix racing car.

[aerohead]

Originally Posted by jamesqf

Don't know who uses that definition, but it seems a misuse of language at best, since the area would be identical to everything you can see from the back.

Yes,the area of the outline is the same regardless of direction as long as it is longitudinal to the car.It's simply a convention to say 'frontal.' It has nothing to do with the front of anything.

[aerohead]

Originally Posted by duncan

Just a small comment

Frontal area x CD gives drag for a non "streamlined" shape,

There are two types of drag - form drag and skin friction

If you can properly streamline a shape such that the air follows the surface, does not detach and rejoins nicely
Which is nearly impossible in a ground vehicle

Then you eliminate "form drag" and you end up with skin friction which is proportional to the "wetted area" and NOT related to the frontal area

*Frontal projected area (A), X coefficient of aerodynamic drag (Cd), = drag factor (CdA), of any shaped vehicle.
*Surface friction drag + pressure drag = profile drag.
*There's also:
*cooling drag (where applicable)
*ventilation drag (where applicable)
*interference drag
*induced drag
*windage drag associated with the spinning wheels
------------------------------------------------------------------------
*When you eliminate pressure drag,your profile drag is reduced to surface friction drag which is associated with the wetted area.
With this graphic for streamline bodies,you can see that pressure drag is eliminated at around l/d= 3.5,then drag goes up as the length increases beyond the l/d 'sweet spot.,' due to the increasing wetted area.

[gumby79]

With this graphic for streamline bodies,you can see that pressure drag is eliminated at around l/d= 3.5,then drag goes up as the length increases beyond the l/d 'sweet spot.,' due to the increasing wetted area.

What is the magic finess ratio in "Ground effect" ??? Because that is were I drive.