Project: The Anal Probe

[Sven7]

Here the white line would be the top edge of the boattail. The straight one is about 13*. I know the curved one breaks 15*. It's not the final version.

If the lip is necessary to maintain attached flow on the steep rear window, will I need another lip at the very end to maintain flow on the similarly sloped boattail? Maybe I'll just have to tuft test it to find out.

Edit, you know what? If I did just a couple feet of boattail this thing would have almost ZERO wake!


And an idea for the front that I sketched out during class today with a couple crayola markers and pencils. Mounting the headlights lower with an S bracket and putting an acrylic fairing over the whole thing will keep them permanently up and permanently aero. It would also be a good time to extend the nose.

With some quality materials and workmanship this thing could look really cool.

Front mods by Tyler Linner, on Flickr

[MetroMPG]

That is cool! Nice work.

Here the white line would be the top edge of the boattail. The straight one is about 13*. I know the curved one breaks 15*. It's not the final version.

It's OK to exceed even 15 degrees - provided you have clean, attached flow through the full curve. If I recall, you can even break 20 degrees in perfect circumstances.

If the lip is necessary to maintain attached flow on the steep rear window, will I need another lip at the very end to maintain flow on the similarly sloped boattail? Maybe I'll just have to tuft test it to find out.

I'll say no. A (large) downstream lip is a band-aid for up-stream problems (or it may just be "styling"). If you have good, attached flow at the end of the car right now, you should be able to extend it, following the curve, and retain attachment to your new "end", wherever you decide to chop it.

[Sven7]

Thank you! The boattail's going to look awkward either way but with that, the aero front and front wheel skirts I do believe I'd be encroaching on the Aero Civic's Cd.

Wondering how much MPG benefit I'd see from these mods. Basjoos claims the Civic gets 95mpg at 65mph. If I could score 60mpg at any speed I'd be pretty happy.

Providing the fuel pump works, here is a list of things to do, vaguely prioritized:

-rear brake pads
-NGK spark plugs
-full belly pan
-alternator on/off
-boattail
-front wheel skirts
-fixed headlights
-aero nose
-MPGuino (when I get a job)
-skinniest/LRR tires available (when I get a job)

[bertb]

Great post; Subscribed!

[Galane]

What if you do something like copying the back end of the Cobra Daytona 427 Super Coupe? Shelby Cobra Daytona 427 Super Coupe

[Cd]

Sven, since your rear glass swings up, you could always open it to the ' perfect' angle and rig some sort of latch on the end of that decklid to lock it.
The sides would then have a gap that needs to be filled, but you could use some creativity and it would work .

You would of course have to trim away the top section of that decklid if you propped it up and fashion one that has the correct slope.

[Cd]

I don't know a thing about aerodynamics, but I would speculate that you might have better attached flow with the curved spoiler design ( if you kept the stock decklid.)
To me it seems like the airflow would sort of trip over this decklid and would be attached more quickly with the curved version, since it follows the airflow curve after this trip and 'grabs' it better.

[Sven7]

Originally Posted by Galane

What if you do something like copying the back end of the Cobra Daytona 427 Super Coupe? Shelby Cobra Daytona 427 Super Coupe

I'm keeping the hatch where and how it is.

Originally Posted by Cd

I don't know a thing about aerodynamics, but I would speculate that you might have better attached flow with the curved spoiler design ( if you kept the stock decklid.)
To me it seems like the airflow would sort of trip over this decklid and would be attached more quickly with the curved version, since it follows the airflow curve after this trip and 'grabs' it better.

I'm not going to open the hatch to drive it- it already has attached flow on the rear window.

Don't know what you mean about the curved spoiler.

...I'm fine with you guys bouncing ideas off me as long as they stay within the scope of the project!

[MetroMPG]

When in doubt, tuft test it!

Good advice for when you start mocking up your boat tail.

As for those LRR tires in your future, are you running 14 in wheels on the car now? If so, you can do worse than to find a set of 165/65R14 Potenza RE92's: http://ecomodder.com/forum/showthrea...eet-19126.html

[Sven7]

Yes, I'd like to do some cardboard mockups soon. 14's.

Edit: If anybody knows, what kind of angle should I expect to get away with on the bottom side of the tail? It would save me some tufting time.