Where the aero template came from...

[Frank Lee]

Automobile Traditions Challenged by First Streamlined Stock Cars

[JethroBodine]

Change a few of the dates and this could have been written recently. Most people still know very little about aerodynamics, myself included, especially before I came here.

[aerohead]

I think that image got a lot of people in trouble.The article came out at the time Chrysler was debutting it's Airflow series cars.
Carl Breer already knew the Airflow wasn't living up to the drag numbers developed from scale model wind tunnel investigations.
We haven't out-lived it yet.The nose was okay,but they ended up with what Hucho refers to as the pseudo-Jaray 'fastback' with too-steep slope and attendant longitudinal attached vortices and high drag.
The Schlor Car mimics this profile almost verbadum and suffers higher than necessary drag.
Breer must have known of Walter Lay's research publised in 1933,although the Airflow's design would have been in 'cement' by then.
If you have access to Fachsenfeld's book of 1951,he illustrates Lay's 'pumpkin seed Cd 0.12.It's a dead ringer for the 'StreamliningTemplate.'

[drmiller100]

so, rise over run, both vertically and horizontally.

I am building a car, and want to keep the flow attached.
From the highest part of the car, I come back xx inches, and down yy inches.

Then I come back bb inches, and down cc inches.

If my car is 45 inches at the highest point, what are xx, yy, bb, and cc to be "safe".

[California98Civic]

Originally Posted by drmiller100

so, rise over run, both vertically and horizontally.

I am building a car, and want to keep the flow attached.
From the highest part of the car, I come back xx inches, and down yy inches.

Then I come back bb inches, and down cc inches.

If my car is 45 inches at the highest point, what are xx, yy, bb, and cc to be "safe".

For a project as intense as building a whole car, I think you would want to buy a copy of Hucho's "Aerodynamics of Road Vehicles" the "Bible" of so many on this site. I got a copy through ILL and photocopied key chapters I needed. With all the details you will want to consider, including stability, I imagine it would be very useful to have for ready, authoritative, reference. I think the rule for the slope after the point of highest camber in the roof is 11-14 degrees. The first generation Insight supposedly had both that angle and the taper about perfect for a production car. You could do worse than to imitate it, I imagine.

[drmiller100]

NONE of the cars haved a straight taper.

And 11 to 14 degrees is not realistic for a final number and still have a reasonable length to the car.

is the curve a parabola? hyperbola? exponential?

[aerohead]

Originally Posted by drmiller100

NONE of the cars haved a straight taper.

And 11 to 14 degrees is not realistic for a final number and still have a reasonable length to the car.

is the curve a parabola? hyperbola? exponential?

*If you'll establish a length specification,then you can use the 'Template' to create the curvilinear outline of the body starting from your highest point.
*Follow the 'Template" out to your 'end' and just slice the body off as you would a loaf of bread.
*The tangent angles will be whatever they are at that position.
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As to a description of the curvature,it would be a convex curve associated with a prolate-ellipsoid streamline body of revolution.

[drmiller100]

car is 45 inches tall (Aren't they all?????).

Cockpit is 9 feet long.

Tallest part of the car is right above drivers head (aren't they all?). Behind the driver is 6 feet.

What is drop in car of the first 2 feet behind driver's head? Next 2 feet? Final 2 feet?

I want to do the sides also. Widest part of the car is at the driver's elbows (aren't they all?). which is 40 inches wide. Need the same numbers.

[JethroBodine]

There is a description of how I did the math in my thread (Project) Boat tail-4 Door Sedan VW Mk2 (1990 Jetta GL) in the first post. First generation didn't turn out very good as I was pressed for time. The second stage is a lot closer, but, again, time( winter) snuck up on me. Can't wait to see what you come up with.

[aerohead]

Originally Posted by drmiller100

car is 45 inches tall (Aren't they all?????).

Cockpit is 9 feet long.

Tallest part of the car is right above drivers head (aren't they all?). Behind the driver is 6 feet.

What is drop in car of the first 2 feet behind driver's head? Next 2 feet? Final 2 feet?

I want to do the sides also. Widest part of the car is at the driver's elbows (aren't they all?). which is 40 inches wide. Need the same numbers.

If someone hasn't beat me to the punch by Saturday,I'll try and have you numbers.
You can print off the Aerodynamic Streamlining Template at a convenient scale,then using 45" as your height at the point of max body camber,pick off your elevations at your 2-ft increments.
If your plan taper is beginning at the same 45" position,then you can do identical taper on the sides as on the roof.
If you want to see an example,do a GOOGLE search for the James Bede-designed,'Litestar,'100-mpg,outrigger motorcycle streamliner,circa 1982.