Aerodynamics of a bug

[al_kaholik]

When are we going to see some more of these for sale!

[chug_A_bug]

and when can you Ship over to Canada...

[evilC]

Us Brits first! Then we'll allow some to float over.

Clive

[Gerrelt]

Sorry guys, the United Kingdom was the first on the list...

For everyone that's got an interest in aerodynamics, I strongly advise you to read this chapter of this book
The Automotive Chassis: System design, chapter AN OVERVIEW OF VEHICLE AERODYNAMICS
Skip over the formulas!

I've read it and it was an eye opener, it's really great.

[SilverBullet]

Want to get A few for Singapore!

[Gerrelt]

Sorry guys, I'm still not producing them in bulk. I am creating them by hand, so no big production numbers.

I did do a wool tuft test, with and without the spoiler. See this article on my webpage: VW beetle wool tuft test

A "spoiler" picture... :

[owdlvr]

Read the page, very interesting effects. The one thing I wish you had done, though, is some more tufts right near the vents at the bottom of the window. It would be very interesting to see how the spoiler effects the intake to the engine bay area.

Hmmm....ship some spoilers to Canada and we'll test for you? ;-)

-Dave

[al_kaholik]

Good effort Gerrelt - working even at "low" speed. I'm impressed

[Steve C]

Hi

Very good results, I wonder if anybody with a roof type deflector could do a test, its very clear from your test that the tufts get sucked down without the spoiler so that part of the test wouldn't need to be repeated.

Steve

[Jadewombat]

Also, has anyone considered doing a mod. like this to the front hood? A lot of the 911 guys do it to vent the oil cooler up front up through the hood as well as create more downforce on the front end. I see this on Nobles and some other cars as well. Not quite sure how it works though, creates an air pocket to disrupt the high pressure zone on the front half of the hood vs. low pressure on the back half?

[evilC]

Originally Posted by Jadewombat

Also, has anyone considered doing a mod. like this to the front hood? A lot of the 911 guys do it to vent the oil cooler up front up through the hood as well as create more downforce on the front end. I see this on Nobles and some other cars as well. Not quite sure how it works though, creates an air pocket to disrupt the high pressure zone on the front half of the hood vs. low pressure on the back half?

The Clan Crusader is often modified with this type of duct but it has an adverse effect in that the downfoce at the front is excessive and although the rear is designed for downforce and Kamm rear the imbalance is noticeable and thus ought to have a full rear wing, that in some instances the rules will not allow.
As Wally says the bugs bodyshape doesn't lend itself to this kind of ducting. To get it to fit would result in the outlet being close to the high pressure area at the base of the windscreen reducing the effectiveness of the duct and causing turbulance that will disrupt wiper and vent function. Given this it would seem better to vent the cooler into the wheel arch (fender) and then vent this away down the side of the car. Holes at the base of the arch or better still a louvre section onto the top would create suction to assist.

Clive

[Wally]

I think its a great idea, but maybe less practicle to realise on a Vee-dub body-wise?

[Jadewombat]

Did some testing with the car just a little while ago. No one could help me film the outside of the car so I just stuck my arm out the window to video the left front part of the car. This is all in anticipation of drilling some holes along the back of the fender. So, thoughts?






Where should I drill the holes, would it help aero flow or not matter? This racer from a few pages ago has holes along the bottom back of the front fenders. I also plan on running some fender flares to match the fender edge with the tires better.

[Wally]

Great testing! Kudo's to you!

I would make some vertical slots in the front fenders as near to the body as possible. Might do some to mine.
The overpressure on the inside of the fenders will not show with the wool on the outside though. Still, you'd think that the flared fenders will grab more air then original ones.
For some reason my car seems to have huge drag at speed. Part might be the air grabbing fenders (and wide tires) is my reasoning.

[Gerrelt]

Nice test work Jadewombat!

Like Wally said, you're talking about two different things. Your tests show how the aiflow is over the fender.
The slots in de fenders are for relieving air "pressure" in the wheel wells.

BTW, the airflow shouldn't be attached all the way to the bottom of the fender. Turbulence behind the fender is good, that means the airflow is de-attached from the fender. The angle of the rear of the fender is too steap for good airflow.

I think you could improve the aerodynamics of your beetle by installing wheels that fall inside the fender. Or install wider fenders. Your wheels stick out a couple of cm's, that can't be good for aerodynamics.

Again, nice work on the wool tuft test! I hope more people do this!