diy vortex generators

[Isaac Zackary]

Ok. But what about compared to a wing?



I'm just looking for an alternative to a boat tail.

[Isaac Zackary]

Originally Posted by ChazInMT

I hope you have fun thinking about these things and I really hope it is a primer for you to really dig in to the fundamentals of aerodynamics so you gain a good understanding of what will work well and what will probably yield only a slight gain.

So I guess it's either boat tail or goat tail.

The main problem with a VW Beetle is the steep rear end. And since it's not a box shape is sure would be hard to do an aero-trailer.

Other than that I figured that I could start with a front spoiler and perhaps wheel skirts. The bottom is already very flat, except around the transaxle. I'm not sure how to deal with the flat windshield.

The main thing I can do is to just drive slower. (Try not to get stuck behind me in traffic .)

[aerohead]

The front of the Bug isn't so bad

Sure you could clean up some things,but the lion's share of drag is due to the roofline.
The Herrod Helper of the 1970s helped a little,providing a little centerline flow reattachment.
Ernie Rogers took it a step further with his 'Bug-Wing' rear spoiler.
Anything to fill in the wake will help.
You can see how Kamm 'fixed' this Adler sedan by lofting the roof up to the streamline pathway

If the roof varies from the streamline pathway any at all,you'll have separation again as in this Citroen

or Z-Car

The doctorate-level aerodynamicists would tell you to attack the back of the Beetle.They've been saying it since 1922.
This VW Student gets to Cd 0.30 in part by keeping to the streamline pathway

For VW's Audi TT,they 'reach up' to the pathway with a spoiler

For a lot more money,VW will push the Audi's roof even higher

For the most amount of money,VW will sell you the 1922 shape!

[Isaac Zackary]

Herod Helpers are still available.



What do you think about the Ron Lummus Racing Street Wing? It costs twice the price but it looks twice as big.



Have you seen those spoiler band things on the backs of German Look Beetles? I wonder if those help at all.



Here's another interesting idea for a Bug:

[freebeard]

The top is too fast, but Porsche used that to advantage the cooling system. If you modify the rear, that may need to be compensated. Maybe with intake scoops over the rear fender, like Tatra.

The middle half of the bottom is relatively flat. The front and rear quarters aren't, and that's half the length. Again, anything done in the rear could potentially affect engine cooling.

If you look under the front, an L-shaped panel on each side would box in most of the underside, but the lower arms and steering linkage runs through that area. In the back a flat diffuser (it should start at the torsion bar housing) could have louvers oriented to pull air up under the transaxle and down under the engine.

Like aerohead says, the windshield is a good compromise for visibility. The fat-fendered sides and the external hinges and drip rails aren't so hot.

One thing I've been thinking about but haven't documented would be a panel or strip that would replace the side chrome trim pieces, using the same mounting holes, that would follow the front fender contour from the parking light and taper to the door handle area, or curve back down to meet the rear fender over an air scoop. With a boxed-in rocker panel it would mimic the Porsche Carrera GT


https://en.wikipedia.org/wiki/Porsche_Carrera_GT

[Isaac Zackary]

I've thought about cooling too. I've heard rumors that the Herod Helper hurts cooling. I like the idea of putting scoops on the rear fenders.

I don't know if the underneath is a good place to get air. I've heard of guys taking away the front fire wall tin thinking that it'll get more air to the fan, only to find out it runs hotter that way. The VW design never took air from underneath. It only expelled hot air there. It seems like an air dam or lowered suspension would cause more vacuum under there. That would be good for sucking out hot air, but not for inducing cool air.

One thing I've always wondered is if it would be practical to direct rammed air from the front into the frame tunnel and into the engine compartment.

[Isaac Zackary]

[freebeard]

One thing I've always wondered is if it would be practical to direct rammed air from the front into the frame tunnel and into the engine compartment.

That would be 1500 cubic feet per minute through a cross section much less than 1 square foot, considering it's full of the shift rod, hand brake cables and gas line. The skin friction and interference drag would choke it.

The louvered diffuser I suggested would only turn over the air trapped under the engine tin. The lower tin would remain (per Bob Hoover) and it offers 1500 cubic feet per minute of activated air to use by any Coanda nozzles that might exist.

Here's my take on the side view you posted. The template is slid back a bit from where you placed it.



Here's another picture with the bike rack that I hadn't posted before:



The Ron Lummus wing will definitely choke a stock cooling system. It's probably intended for running with the hood off.



This is standard race practice. It eventually grows into a rectangular box that completely encloses the engine. But it's for stability rather than low drag, so there is no plan taper, and the side plates are longitudinal instead of tapering off the drip rail.

The rear view out of a half-body of revolution is problematic. I prefer a Tropfenwagen style tail. Here's what happens to the rear view. I made a cone with the same cross-section as the stock back window. The vertex is forward of the rear-view mirror the same distance as reflected to the driver's eye. The intersection with the added tail is flat on the top and bottom and curved on the side as shown, even though the back window's top and bottom are curved.



The visual cone is based on a big back window, even though an oval window is shown.