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Collaboration: Underbody and wheel Fairings WITH Boat Tail for a MkIV Volkswagen Jetta (and possibly Golf) Answered

The underside of your typical car will not have any skin/covering -- the outer skin of your car is known as a fairing and that is how I'll refer to it from this point forward ;) These open crevasses etc. create a great deal of drag force and turbulence to high speed air. This added drag is significant enough to warrant some manufacturers to install aluminum plates covering the entire undercarriage (which add weight).

My big project over the next few months will be prototyping a partial fairing for the underside of my car. Additionally, I will be constructing wheel fairings for all four wheels an begin construction of a boat tail (likely in a Kammback Style. I am open to feedback, suggestions and comments of any type - that is why I'm posting here and will be updating my progress.

This is a tentative list of things that need to be done - feel free to add.

1. Acquire and install material for rear wheel fairing (Prototype has been Completed)
2. Front Wheel Fairing
3. Start Patchwork Under Tray (This is a huge project)
4. Relocate External Mirrors
5. Cover Front Grille as much as possible
6. Buy ScanGaugeII (I promised myself for my birthday)

1. No Permanent "Stock" body changes (no visible holes etc.)
2. Must Be Removable Within 30 Minutes or so without special tools or lifting vehicle
3. Must Collapse and Fit in Trunk
4. Would like the deadline to be BEFORE a cross country trip (South Florida to San Francisco)

Here's what's on the table:
1. Corrugated Plastic
2. Possibly Fiberglass
3. Flashing (as suggested)
4. Clear Plastic Sheeting (similar to what is use for convertible rear windshields)

I'm current exploring non permanent adhesives and methods of application/removal. This adhesive would be used in tandem with two part snaps. I have also decided on using fold over nuts where applicable.

Why a Partial Fairing
I discovered that some of my exhaust components are the lowest points of my car. Considering the temperatures of these components, extra cost of materials AND the necessary curves to fit these components - I have decided to make this first prototype simple (hopefully all 2-d shapes).

Honestly, I'm in college - a lot of my money goes to tuition and books (and engineering books typically come with a killer price tag). My goal is to make this cost effective so that someone else can mimic my efforts on their car/truck/etc. OR apply this to their MkIV directly. I will supply dimensions of the vehicle AND dimensions of my overall product as completed.

One day, this will become an instructable. If a particular step warrants its own instructable -- I will post it ;) If someone has a MkIV Jetta and wishes to collaborate, please contact me. Having more brain power to come up with robust and unique solutions is a great asset.

The Probe V - Cd= .137
70+mpg Civic Hatch Modifications (Cd estimated around .16)

This photo below is a skid plate available for Mark IV Jettas and Golfs -- cost: $300+. It is made from 3/16" plate aluminum and notice that there are no undercarriage vents. This is good news for me as heat management is a major concern. This plate is available here

As always, I'm open to suggestions etc. It's somewhat of a big project, so I'm taking it slow and steady so I don't burn out with everything else going on :P

Other Updates as of 3/30/07

-Scratched previous task list - replaced with modification task list
-Added boat tail and wheel fairing to overall project
-Added Inspiration Links
-added constraints category
-updated fastener category
-updated materials category



11 years ago

Well, a lot has happened since I originally posted this. I've rearranged my goals, done quite a bit of research and spoken with a lot of people. Please note the changes in the post. So... anyone know of a decent adhesive that won't damage clear coat? :P


11 years ago

I had a MKIV GTI, I thought it had a plastic lower engine bay cover from the factory. It maybe something you could purchse or find in a salvage yard. maybe I'm wrong.

anyways, I have a suggestion for fasteners. here's a link http://www.dfcis.com/st-1200/index.html . they are quarter turn fasteners called Dzus fasteners. I know they are popular in dirt track stock car racing so they will hold up.


Reply 11 years ago

I've used flush dzus fasteners in the past (my avatar -- that shell connects to a frame with 5 of 'em :P). That's actually a good idea -- I could rivet on the male half. But the mount side may be more difficult - I would prefer to not mount them in any permanent fashion :P Thanks for the input ;)

Yes, there is a factory splash shield -- but that only covers a relatively small portion of the undercarriage. That picture of the skid plate was just to show that heat will (hopefully) not be an issue :D


11 years ago

As far as cheap and easily found materials go, you may wish to consider using aluminum flashing. It is still light weigh and it is easy to form into whatever shape you are looking for. Then you can use pop-rivets to create larger sections than the typical 12" width will allow.