Aeromodability of a VW Bug?

[ecomodded]

I have a roof spoiler on my new beetle, I have deduced this, having the air flow detach above the window not only reduces drag caused by lift but reduces the drag caused by air that no longer passes over the rear window and trunk = Less surface area in the airflow and in the Beetles case less lift.
My car below

[kach22i]

Originally Posted by ecomodded

My car below

Nice car.

Another, more detailed study.

Automobile pictures by kach22i - Photobucket

[Quasimoto]

This post by Phil is right on this subject http://ecomodder.com/forum/showthrea...lips-2685.html

[Frank Lee]

Originally Posted by kach22i

AWESOME!

JMPVW73, very informative posts, a breath of fresh air.

Frank Lee, I'm not going to beat this horse till it's dead. I only ask that you look at the following images and maybe click the link to where the original VW picture is. It takes little imagination and average levels of observation to predict the results of the added horizontal planes, call them wings, spoilers or what ever suits your fancy.

Beetle Aerodynamics / Roofspoiler
Beetle Aerodynamics / Roofspoiler

Gee, with expert advise like that, how could anyone go wrong?

[kach22i]

Originally Posted by Frank Lee

Gee, with expert advise like that, how could anyone go wrong?

Are you talking about the website I provided a link to, or the mark-ups I did? I don't claim to be an expert, but enjoy learning.

Beetle Aerodynamics / Roofspoiler


I like the thinking behind Gerrelt's Garage, and the projects they show.

Creating a roof spoiler

I decided to create my own roofspoiler.................although the goal is to reduce drag, the design must be aesthetically pleasing too!

[Frank Lee]

If you enjoy learning you could maybe give what I said some consideration.

[kach22i]

Originally Posted by Frank Lee

If you enjoy learning you could maybe give what I said some consideration.

I'm learning what you are really about.

If you have something constructive to say, then say it. The negative tone does nothing for me.

I'm sticking to what I first said, the wing posted would do more good over the rear window than under it.

EDIT-1: I think this is related to the same general topic.

http://www.merkurencyclopedia.com/Me.../aerodyne.html

In a nutshell, the information shared with me by the Ford aerodynamic office in Dearborn, (data from the FOG wind tunnel) indicates that there is no negative lift (down force) generated by the bi plane nor the single wing aero package. The bi plane wing is an adaption from Fords first aero research vehicle done in Germany in the mid 70's. It had the biplane wings and the look in the backlite and C pillars. The car also had active aero skirts and front spoilers...etc etc. very very advanced. The bi plane wing is designed purely for reduction of drag only. For its time the XR4 has extremly low drag numbers. .328 for production ride height bone stock car. With a frontal area of 21 sq feet (same as mustang) our cars are rather slippery. The engineers and stylists did an excellent job of working together for some good comprimises.

Merkur XR4Ti biplane spoiler
http://www.curbsideclassic.com/curbs...ats-in-a-name/

[Frank Lee]

Some of you have taken the position that a larger trailing wake is lower drag than a smaller trailing wake. Doesn't make sense to me.

The bi-plane wing is great. Ask yourself why it isn't coming off the top of the window?

If you have something constructive to say, then say it. The negative tone does nothing for me.

Everything I've said is constructive. You are asking me to repeat myself yet you've shown you haven't thought about what I already put out there.

Oh well, I've done what I care to do about it.

[kach22i]

Originally Posted by Frank Lee

Some of you have taken the position that a larger trailing wake is lower drag than a smaller trailing wake. Doesn't make sense to me.

The trailing wake in all examples given starts at the top of the rear window.

From that point we have several options;

1. Roof spoiler, creates vortex which eventually manages to pull the flow downward in a more controlled manner.

2. Plane above the window (should tilt down 10 degrees but is shown flat) which extends the length of the car. A longer car should move through the air better, but with some additional surface drag. This is similar to the aero-mods many people are doing in this forum.

3. A flat plane, marketed as a wing, secured tight to the body below the rear window, and completely out of any known air flow pattern. The pattern we do know about is turbulent and full of drag.

.................................................. ..................

If we could put the VW Beetle though a wind tunnel ourselves and experiment with many different positions and shapes, spoilers, wings and planes, we might come up with something none of us could have ever predicted.

I did this overlay (not to scale) to get an idea of what possibilities may be out there.

Automobile pictures by kach22i - Photobucket

[UFO]

Originally Posted by kach22i

The trailing wake in all examples given starts at the top of the rear window.

From that point we have several options;

1. Roof spoiler, creates vortex which eventually manages to pull the flow downward in a more controlled manner.

That sounds like a "vortex generator", which may induce more drag than it reduces. My understanding of the roof spoiler is to provide a sharper cutoff to the airflow to reduce some of the drag caused by air partially detaching along the steeper back slope. By detaching the air completely you still have the full drag of the entire frontal area.

Originally Posted by kach22i

2. Plane above the window (should tilt down 10 degrees but is shown flat) which extends the length of the car. A longer car should move through the air better, but with some additional surface drag. This is similar to the aero-mods many people are doing in this forum.

Otherwise known as a Kamm back, and if long enough makes a huge difference.

Originally Posted by kach22i

3. A flat plane, marketed as a wing, secured tight to the body below the rear window, and completely out of any known air flow pattern. The pattern we do know about is turbulent and full of drag.

Ernie Rogers did a flat spoiler at the window base on his New Beetle and demonstrated a Cd reduced from 0.39 to 0.30, similar if not slightly better than the VW Golf.