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Old 04-22-2008, 06:34 PM   #11 (permalink)
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Quote:
Originally Posted by RH77 View Post
So last night I started tinkering with the aero challenges on this car...

I pulled the splash guards and saved them for future use.

Issue: The rear guards were part of the wheel well. Now I have a big hole in the rear 1/3 of the well.

Could this be beneficial to relieve pressure in this area, or could the air get stuck under the rear of the car and create additional drag?

RH77
I can only tell you what I did.

On the Honda Civic the rear bumper is basically the back half of the wheel well, so that area is wide open. I used aluminum sheeting and directed the air more smoothly to the bottom of the bumper. That way it deals with that issue and gains some of the advantages of a rear bellypan. Of course, your car may be different.

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Old 04-22-2008, 06:59 PM   #12 (permalink)
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Actually, that sounds exactly like what I have. On the Passenger side, though, the muffler is in the way. IIRC, most Civic designs were similar. Is this a problem you had to work around?

RH77

Quote:
Originally Posted by Arminius View Post
I can only tell you what I did.

On the Honda Civic the rear bumper is basically the back half of the wheel well, so that area is wide open. I used aluminum sheeting and directed the air more smoothly to the bottom of the bumper. That way it deals with that issue and gains some of the advantages of a rear bellypan. Of course, your car may be different.
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Old 04-22-2008, 07:28 PM   #13 (permalink)
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Quote:
Originally Posted by RH77 View Post
Actually, that sounds exactly like what I have. On the Passenger side, though, the muffler is in the way. IIRC, most Civic designs were similar. Is this a problem you had to work around?

RH77
Yeah, I had to make a much smaller mod on that side.

http://corporate.honda.com/press/art...=2005083040359

If you look at the pick in the link, where is a small (about 4") extension on the wheel well to direct the strongest air, I assume. Behind and below that I added some small mods, including covering areas above the muffler. Basically I started from the bottom of the bumper and sloped upward and forward to one point or another, all along the back.

The gas tank covers the entire middle portion perfectly, so I didn't have to do anything with that.
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Old 04-22-2008, 10:28 PM   #14 (permalink)
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Quote:
Originally Posted by RH77 View Post
I pulled the splash guards and saved them for future use.
Good. That's what I would have done too.

They may come in handy as a base for a boat tail shape behind the wheel later on.
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Old 04-23-2008, 12:17 AM   #15 (permalink)
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I agree with Otto on the wheel boattails.

Splashguard Boattails

I would go to Homedepot and pick up some cheap pink insulation foam (polyurethane I believe). The lightest structure will be one built like a traditional boat: central backbone with ribs, all sheathed with foam stripping.

Sand and shape the sheathing, then apply a thin layer of fiberglass and epoxy resin. Once the outer shell has hardened, remove the skeleton and ribs. Using a depth gauge, sand out the foam sheathing to leave ~1/8-1/4" of material to be used as a core. Apply the same fiberglass layer on the inside as out.

The best method I've come up with for attaching the structure would be to use the original splashguard mounts, lay painters tape trailing the fender sheetmetal to protect the paint and apply tons of hot glue. Bolt up and "stick" the structure to the car and use colored duct tape or gap seal tape to smooth the transition.

Rear Bumper

If you decide to take this route, I would highly suggest using a spare bumper from a junkyard as this mod will be irreversible.

That rear indentation would be dealt with best through removal. If that indentation is gone, you have the perfect spot to create a rear diffuser. This will probably only be worth your while if you create a smooth and contoured underpan that spans the whole vehicle length first. In fact, I wouldn't even consider this mod until wheel skirts, front splitters, wheel boattails, and side skirts had been fully developed.

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Old 04-23-2008, 08:10 AM   #16 (permalink)
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Any pics?

Quote:
Originally Posted by Arminius View Post
I can only tell you what I did.

On the Honda Civic the rear bumper is basically the back half of the wheel well, so that area is wide open. I used aluminum sheeting and directed the air more smoothly to the bottom of the bumper. That way it deals with that issue and gains some of the advantages of a rear bellypan. Of course, your car may be different.
Do you have any pics how you did that ? Did you cover wide open area to the bottom of your rear bumper including the lowest point of bumper (right by the wheel)?
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Old 04-23-2008, 11:33 AM   #17 (permalink)
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Quote:
Originally Posted by LostCause View Post
I agree with Otto on the wheel boattails.

Splashguard Boattails

I would go to Homedepot and pick up some cheap pink insulation foam (polyurethane I believe). The lightest structure will be one built like a traditional boat: central backbone with ribs, all sheathed with foam stripping.

Sand and shape the sheathing, then apply a thin layer of fiberglass and epoxy resin...
Since this is not a structural part, but merely fairs the airflow behind the wheel, you could probably dispense with the fiberglass and epoxy, but rather just spray the foam with black paint and call it a day.

Perhaps Great Stuff foam from a can would work, as it's sculptable and paintable, and is very adhesive by itself. I have not done this yet, but imagine that a simple mould could be made of Coroplast or smooth plastic, then squirt the Great Stuff and let it cure, then peel off the mould, then spray with black paint. If/when the fairing gets whacked, respray and touch up.
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Old 04-23-2008, 01:41 PM   #18 (permalink)
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Quote:
Originally Posted by holypaulie View Post
Do you have any pics how you did that ?
Hi,

I'm working on learning how to post pics. Truth is I'm almost never on the computer, and I've used my digital camera only once. How to coordinate the two is known only to Mrs. Arminius. Yes, I am a caveman, and I like it that way.

Quote:
Did you cover wide open area to the bottom of your rear bumper including the lowest point of bumper (right by the wheel)?
The mods I did were in that area, but I did not cover the entire area, as some have done. My wife doesn't want the car to appear modded, so all the mods I do have to be unnoticeable. This car will be hers when I buy an electric car sometime in the next 3-4 years, so I want to keep it the way she likes it.

In the Civic, like so many other cars, the back bumper is actually just a metal bar covered by a huge piece of plastic. That piece of plastic is what the average person is calling a "bumper," but to ecomodders and hypermilers it's known as "the parachute." What I did was attach the sheeting to the bottom of the bumper, and then up to the bottom of the car, so that it just covered that huge "parachute." In addition, I sloped it forward so that the air hits a 45 degree angle, rather than a vertical wall. I intended to test the mod, but the summer gas formulation came out at the same time, so any tests I would do would also show improved gas mileage because of that, so I can't actually test what I did. Right now I appear to be getting about 80 more miles on this tank, but I'm only 3/4 of the way through it. A couple of unexpected trips in the city could mess it up, so I don't want to jinx it.
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Old 04-23-2008, 01:51 PM   #19 (permalink)
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Oh yeah, take a look at Harpo"s rear bumper in this thread and you will see what my "parachute" looked like.

http://ecomodder.com/forum/showthread.php?t=1601

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