Cd and blunt front ends

[Cd]

Not sure what you mean Phil. Are you saying that it is beneficial for the roof to slant at an upwards angle rather than be flat or slanted down ? Also, the rake makes the angle of the windshield even more vertical.

The radius on the edges of the Camaro on post #113 seem closer to 10.7 mm rather than 107mm, especially those shap sides !

Not trying to be 'smart', but rather I'm just too dumb to understand this stuff. It all seems to baffle me how that things seem to cotradict sometimes.

Phil : surely that was supposed to be 10 point 7 millimeters right ? 107 mm is huge !!

[aerohead]

Originally Posted by Cd

Not sure what you mean Phil. Are you saying that it is beneficial for the roof to slant at an upwards angle rather than be flat or slanted down ? Also, the rake makes the angle of the windshield even more vertical.

The radius on the edges of the Camaro on post #113 seem closer to 10.7 mm rather than 107mm, especially those shap sides !

Not trying to be 'smart', but rather I'm just too dumb to understand this stuff. It all seems to baffle me how that things seem to cotradict sometimes.

Phil : surely that was supposed to be 10 point 7 millimeters right ? 107 mm is huge !!

Cd,with the rake,the top of the roof is slanted down towards the front and air parallel to the ground is "attacking" it,right up to the point of maximum height at it's rear,after which it will separate for sure,unless the "downwind" or "leeward" portion of the roof is shaped close to what Dr.Kamm recommended,or there is something to re-attach to.----------------- Even if the area above or around the side of the windshield has just a slight radius,the air may stay attached if it's within the "wedge" of a body which is still growing in cross-sectional area.Kinda like the "Prowler" or PT Cruiser,both of which just get wider and wider the further back you go.--------------- You "penetrate" the air okay this way,but end up with a large powerful wake of dramatically low pressure which holds you back.------------- For the hot rod,the wake gives some directional stability,as the transom of a ship does,with the wake drag helping to pull the stern straight back behind the ship.----------------------- With respect to the 107mm radius,at 25mm per inch its a little over 4-inches radius.I'm pretty sure Volkswagen got way with much less on their first-gen Rabbit.---------- The Oscar Meyer Wienermobile that just got posted about has the "ideal" nose and windshield if you ignore the lower portion.

[ECONORAM]

Originally Posted by Cd

Just think - the EV1 had a drastic tear drop shape from not only the sides , but the top as well, a full belly pan, no grill opening, wheel skirts ..etc, yet was only slightly sleeker than this old beat up* '79 Camaro.

* Just look at how rough the edges are below the 'bumper'.

I just don't get it.

Here is another blast from the past that bucks the aero trend: 1970 Dodge Charger Daytona. The Cd was 0.28. The Plymouth Superbird and Dodge Charger Daytona, supercars
I might have to do some digging in my old Intro to Aero book to figure out the blunt nose vs teardrop question...

[jcp123]

The idea of a blunt front end seemed counterintuitive to me until I thought of the raindrop...the "fat" end breaks the air, it's the shape behind it that makes it aerodynamic. It seems to almost make sense now.

[Cd]

Originally Posted by ECONORAM

Here is another blast from the past that bucks the aero trend: 1970 Dodge Charger Daytona. The Cd was 0.28. The Plymouth Superbird and Dodge Charger Daytona, supercars
I might have to do some digging in my old Intro to Aero book to figure out the blunt nose vs teardrop question...

If you remember the Charger 500, it was the car that proceeded the Daytona.
Dodge engineers grafted a SoperBee grille onto the front end of the Charger to get rid of the 'parachute ' effect that the standard front end had.
They also gave the car the flush mounted back window versus the open design.
The car was pretty slick, but they needed it to be even sleeker.
In an all out effort, they gave the car that famous/infamous boat shaped front end that became the Daytona.
If they could have just smoothed the heck out of the front end and plugged it up, versus go with a pointed front end, then you can bet gold that they would have chosen to do that.
But they didn't. Something about that pointed nose worked better than the blunt one.

It certainly wouldbe interesting to see the data on the designs !

You just might find it on this site, since it has lotsof info. from the testing that was done in the wind tunnel on those cars :

Aero Warriors - The G-Series Wind Tunnel Test Report Figures In Thumbnail Format

[Frank Lee]

They needed downforce too.

[winkosmosis]

Birds don't have blunt front ends

[MechEngVT]

Originally Posted by Cd

If they could have just smoothed the heck out of the front end and plugged it up, versus go with a pointed front end, then you can bet gold that they would have chosen to do that.
But they didn't. Something about that pointed nose worked better than the blunt one.

Remember the Charger 500 didn't have the 2 1/2 foot tall rear wing on it either. The bullet nose of the Daytona/Superbird does add front downforce, which would be critical in maintaining handling balance with the obvious amount of downforce that the rear wing could potentially generate.

In addition to that, NASCAR racers of the era probably couldn't tolerate nearly as much of a "grille block" as the current racers typically run, limiting how much smoothing and plugging could be done. With the bullet nose the Daytona/Superbirds were bottom breathers; they had a lower forward-projecting air dam at the bottom of the front end above which was the cooling inlet. Don't forget also that they both had rearward-opening "scoops" on top of the front fenders above the tires that allowed the cooling air to escape from the tops of the fender wells (but only because the fendertop had to be cut open to clear the tires on the race cars).

[Old Mechanic]

I worked for a Chrysler dealership when the winged cars first came out. 18 years old until November 69.

regards
Mech

[aerohead]

Originally Posted by Cd

If you remember the Charger 500, it was the car that proceeded the Daytona.
Dodge engineers grafted a SoperBee grille onto the front end of the Charger to get rid of the 'parachute ' effect that the standard front end had.
They also gave the car the flush mounted back window versus the open design.
The car was pretty slick, but they needed it to be even sleeker.
In an all out effort, they gave the car that famous/infamous boat shaped front end that became the Daytona.
If they could have just smoothed the heck out of the front end and plugged it up, versus go with a pointed front end, then you can bet gold that they would have chosen to do that.
But they didn't. Something about that pointed nose worked better than the blunt one.

It certainly wouldbe interesting to see the data on the designs !

You just might find it on this site, since it has lotsof info. from the testing that was done in the wind tunnel on those cars :

Aero Warriors - The G-Series Wind Tunnel Test Report Figures In Thumbnail Format

The Daytona's nose was developed by Chrysler Aerospace personnel,at the E.Chelsea,MI proving grounds high speed oval track.They duct-taped plywood over angle iron to create the famous nose which also sports Walter Korff's ( Lockheed Aircraft Co.) maximized grille-block,with air-tight,diverging inlet duct.
Also,the rear spoiler is mounted high,where it's in "cleaner" air,and can be made smaller and still produce the required downforce with lower drag.
Smart guys!