frontal area vs cd

[Frank Lee]

In your definition, where does the "front" of the car end?

For that scenario it depends on the velocity and strength of the vehicle (amount of deformation) plus the strength of the wall (amount of penetration).

[freebeard]

http://justacarguy.blogspot.com/2016/02/even-gt-40-was-crash-tested-at-41-mph.html

[Vman455]

Originally Posted by Frank Lee

For that scenario it depends on the velocity and strength of the vehicle (amount of deformation) plus the strength of the wall (amount of penetration).

Clarification: if "frontal area" is not the same as cross-section (as jamesqf's first post indicates: "It's not frontal area, but cross section"), where does the front end?

[aerohead]

Originally Posted by Vman455

Clarification: if "frontal area" is not the same as cross-section (as jamesqf's first post indicates: "It's not frontal area, but cross section"), where does the front end?

With quasi-streamline half-bodies and streamline half-bodies,the maximum area cross-section WOULD occur with the projected frontal area


With something like the Morelli shape,the maximum cross-section would NOT occur with the projected frontal area.

By establishing Cd based upon projected frontal area,we keep apples apples,and oranges oranges.

[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

[freebeard]

Form drag isn't eliminated, it's minimized. So what are the relative proportions of drag/friction?

[gumby79]

This is a good example the frontal area being at the rear. Frontal area will get smaller each time a stage is released

Frank Lee
Quote:
In your definition, where does the "front" of the car end?
on this 🚀 at the rear including the stabilizing fins just in front of the nosal

For that scenario it depends on the velocity and strength of the vehicle (amount of deformation) plus the strength of the wall (amount of penetration).

The way you described the hole should be 1-4" in Diameter with no penetration misconception

The brick wall ex would have a round hole 33' Diameter plus tailfins fact

[Peter Hill]

Simples just go buy a car that starts with world class CDx, less than 6 SqFt.

from the Wiki

CdA sqft CdA m2 Automobile model
2.04 sq ft 0.190 m2 2011 Aptera 2 Series
2.10 sq ft 0.195 m2 2013 Urbee 2[
2.50 sq ft 0.232 m2 1986 Twike
2.54 sq ft 0.236 m2 2002 Opel Eco-Speedster
2.69 sq ft 0.250 m2 2009 Loremo
2.784 sq ft 0.2586 m2 2010 Edison2 Very Light Car
3.00 sq ft 0.279 m2 2011 Volkswagen XL1
3.95 sq ft 0.367 m2 1996 GM EV1
5.00 sq ft 0.465 m2 2005 Mercedes-Benz Bionic
5.10 sq ft 0.474 m2 1999 Honda Insight
5.40 sq ft 0.502 m2 1989 Opel Calibra (8 valve)
5.58 sq ft 0.518 m2 1993 Mazda RX-7 FD (base model)
5.70 sq ft 0.530 m2 1985 Subaru Alcyone/XT/Vortex
5.71 sq ft 0.530 m2 1990 Honda CR-X Si
5.74 sq ft 0.533 m2 2002 Acura NSX
5.76 sq ft 0.535 m2 1968 Toyota 2000GT
5.80 sq ft 0.539 m2 1986 Toyota MR2
5.81 sq ft 0.540 m2 1989 Mitsubishi Eclipse GSX
5.86 sq ft 0.544 m2 2001 Audi A2 1.2 TDI 3L
5.88 sq ft 0.546 m2 1990 Nissan 240SX / 200SX / 180SX
5.90 sq ft 0.548 m2 2015 BMW i8 [142]
5.92 sq ft 0.550 m2 1994 Porsche 911 Speedster
5.95 sq ft 0.553 m2 1990 Mazda RX7
5.96 sq ft 0.554 m2 1993 Mazda RX-7 FD R1(R2)

The first 9 on the list are rocking horse poo and unicorn horns. Others like the Toyota 2000GT are £1 million and/or very rare, less than 1000 Porsche speedsters. The i8 is a bit expensive to start chopping around.

Then make a choice between 2 seat or 2+2. But beware of the 8 valve Opel Calibra it's only got 1/2 a cooling system so most of it's advantage over the 16V/turbo/V6 models is cooling / engine bay drag. Honda Insight also has small radiator with blanking plate.

Mazda RX7 FD appears 3 times with different "aero" trim. So now you have a choice of about 10 cars.

Lowering a car only reduces the frontal area by the area of the tyre that is hidden. 25mm drop with a 205mm tyre = 4 x 0.205 x 0.025 = 0.02 m².

[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.

[samwichse]

Originally Posted by Peter Hill

Simples just go buy a car that starts with world class CDx, less than 6 SqFt.

from the Wiki

CdA sqft CdA m2 Automobile model
2.04 sq ft 0.190 m2 2011 Aptera 2 Series
2.10 sq ft 0.195 m2 2013 Urbee 2[
2.50 sq ft 0.232 m2 1986 Twike
2.54 sq ft 0.236 m2 2002 Opel Eco-Speedster
2.69 sq ft 0.250 m2 2009 Loremo
2.784 sq ft 0.2586 m2 2010 Edison2 Very Light Car
3.00 sq ft 0.279 m2 2011 Volkswagen XL1
3.95 sq ft 0.367 m2 1996 GM EV1
5.00 sq ft 0.465 m2 2005 Mercedes-Benz Bionic
5.10 sq ft 0.474 m2 1999 Honda Insight
5.40 sq ft 0.502 m2 1989 Opel Calibra (8 valve)
5.58 sq ft 0.518 m2 1993 Mazda RX-7 FD (base model)
5.70 sq ft 0.530 m2 1985 Subaru Alcyone/XT/Vortex
5.71 sq ft 0.530 m2 1990 Honda CR-X Si
5.74 sq ft 0.533 m2 2002 Acura NSX
5.76 sq ft 0.535 m2 1968 Toyota 2000GT
5.80 sq ft 0.539 m2 1986 Toyota MR2
5.81 sq ft 0.540 m2 1989 Mitsubishi Eclipse GSX
5.86 sq ft 0.544 m2 2001 Audi A2 1.2 TDI 3L
5.88 sq ft 0.546 m2 1990 Nissan 240SX / 200SX / 180SX
5.90 sq ft 0.548 m2 2015 BMW i8 [142]
5.92 sq ft 0.550 m2 1994 Porsche 911 Speedster
5.95 sq ft 0.553 m2 1990 Mazda RX7
5.96 sq ft 0.554 m2 1993 Mazda RX-7 FD R1(R2)

The first 9 on the list are rocking horse poo and unicorn horns. Others like the Toyota 2000GT are £1 million and/or very rare, less than 1000 Porsche speedsters. The i8 is a bit expensive to start chopping around.

Then make a choice between 2 seat or 2+2. But beware of the 8 valve Opel Calibra it's only got 1/2 a cooling system so most of it's advantage over the 16V/turbo/V6 models is cooling / engine bay drag. Honda Insight also has small radiator with blanking plate.

Mazda RX7 FD appears 3 times with different "aero" trim. So now you have a choice of about 10 cars.

Lowering a car only reduces the frontal area by the area of the tyre that is hidden. 25mm drop with a 205mm tyre = 4 x 0.205 x 0.025 = 0.02 m².

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.