Honda Fit - My first Aero Mod Project

[botsapper]

I concede not being 'airtight' on the strict boat tail theories. I was intrigued by complex F1 rear airfoil designs. They are entirely 'separate' structures highly sculpted & tuned for down force but they are also used for turbulence control. The deep vertical end plates close a 'loop' around the rear, supposedly to shape & minimize turbulences and vortices. It reminded me of closed box wing designs. Closed wing surfaces has the benefit of minimal wingtip vortices which occur with conventional wings or corner body shapes, associated with induced drag. Closed flow surfaces, eliminates wingtip or corner drag. I also envision a tighter flow @ higher speeds. A hollow boat tail, if you will. Easier to fab & still allow to access rear hatches. Rear lights visibility, iffy.

[aerohead]

Originally Posted by botsapper

I concede not being 'airtight' on the strict boat tail theories. I was intrigued by complex F1 rear airfoil designs. They are entirely 'separate' structures highly sculpted & tuned for down force but they are also used for turbulence control. The deep vertical end plates close a 'loop' around the rear, supposedly to shape & minimize turbulences and vortices. It reminded me of closed box wing designs. Closed wing surfaces has the benefit of minimal wingtip vortices which occur with conventional wings or corner body shapes, associated with induced drag. Closed flow surfaces, eliminates wingtip or corner drag. I also envision a tighter flow @ higher speeds. A hollow boat tail, if you will. Easier to fab & still allow to access rear hatches. Rear lights visibility, iffy.

If I had some loose cash,I'd pay some grad students to model it and put it in a tunnel for investigation.
It has that "OMG I've got to have that!" appeal.
I've seen two aircraft which use the wing design.
NASA even experimented with the 'large eddy breakup device LEBU' although it straddled the fuselage rather than attach at the rear.
I could see the 'fast and the furious set' all over this thing.
If you build it,I recommend you stay away from the San Fernando Valley,you'll need Police protection to keep the chicks off of you!

[Tofuman]

Wow, those photoshop skills are great. Good luck with the Fit.

[wyatt]

Hi stockrex,
15 degrees is the general rule of thumb on taper angle on a boattail-like extension. I have added a SedanKamm to my car, it comes off a good radius at the top, and as it is now, the top half is 10 degrees and the second half is about 13 degrees, and there is good attached flow all the way to the end. It is 4 feet long and it gets me about 6% better FE at 60 mph and 12.5% less drag. I attached it with duct tape. If your car is nicer than my 1994 Suzuki Swift, you may want to consider attaching your boat tail to something more like a bicycle rack that attaches by clips to the edge of your trunk or hatch.
I have considered a "wing" like the ones in the pictures too. I just don't know at what angle the flow will re-attach if there is a sizable gap to see through, or how long I would have to make it so the flow would re-attach... the way I have it now works pretty well, but for a more permanent setup, I would look into something with more strength than duct tape (although I have had this on for a month now, and the duct tape seems to be holding up... original tape too). Look into Basjoos' car (if you haven't already) and see the things he has done. Everyone serious about aeromodding eventually winds up going his route... smooth under belly, wheel skirts, boat tail... If I am getting some looks with the little bit of a tail I have, you can expect a whole lot more with a full out boat tail... like instead of having people look at your car, they might talk to you about it!

[interestingstuff]

I would really like to get "Rear Wheel Covers" aka skirts for my wheels. (I have a Base Fit too.) However, they need to look good and be well-made. I think I'm not the only one who would be interested. I posted a thread on this over at fitfreak.net a while back.. are you a member?

Another (easy) thing you can add to your list is flat hubcaps - like the pizza tins or simple moon caps.

Some people drop their fits ridiculously low.. I'm not into that but I have been thinking about a front air dam. Not sure I would contemplate blocking off the grill.. but hey someone's gotta make the fit version of the aerocivic! Go for it!

Personally I tried over-inflating my stock dunlops and didn't find good results with that.

BTW, Botsapper - you used the sport model for your illustration. The sport has the spoiler (amongst other things like the sideskirts) that the base model doesn't.

[NeilBlanchard]

Botsapper -- your images are indeed a huge asset, as they make good aero look good! You might send a few of the images to Honda to get their creative juices flowing?

A couple of comments from the peanut gallery:

The front wheels, being exposed, should probably not have any openings around the outer part of the rim. The top of a spinning wheel has 2X the forward motion of the rest of the car, and either the openings have to be pointing the "right" way on each side of the car (which necessitates mirrored rims, doubling the cost); or, they should be smooth on the outer part at least, IMO. The aftermarket wheels for a Prius (elsewhere on these pages) have a smooth hole right at the center (and one also for the valve stem) -- I think these are pretty ideal.

The trailing side of the front wheel opening would be better to be treated like the original Insight.

The rear wheel strakes should be made larger, I think. The trailing edges can "link in" to the ring/boattail. My Coroplast (and ugly tape) units seem to be working quite well, and they clear all the curbs I have been around, so far:

[walesjd]

1. Can you say where you got or how you made our smooth rims?

2. Do you know how much fuel economy improvement you got out of each mod?

[kach22i]

I like the design posted, and want to believe fast moving outer air would attach to the wing ring, while other air closer to the body would be sucked inward.

Just a want, and would need to be tested.

Maybe a giant pusher fan would get the job done.

[aerohead]

Originally Posted by kach22i

I like the design posted, and want to believe fast moving outer air would attach to the wing ring, while other air closer to the body would be sucked inward.

Just a want, and would need to be tested.

Maybe a giant pusher fan would get the job done.

Theoretically, as a 'ventilated' structure, the flow is going to separate at the same location. There's no way to isolate the boundary layer from the extreme and sudden positive pressure spike of the truncation.
If it were air-tight, the flow would converge, decelerate as on a box-cavity, and when it did separate at the new trailing edge, be slower, at a much higher pressure, smaller wake, higher base pressure, and lower overall drag.
As she sits, it's an unknown quantity. Beautiful though!

[freebeard]

I need to perfect my attaching skills, as I drive all hwy and don't this to hit someone at 80 mph.
....
ok, how do I attach the pizza pan stuff to the wheels? I took off the stock wheel covers.

Wrong end of the car, but look at the spacing of the fasteners (with fender washers) and how thick the metal in the turnbuckle brackets is.

Best attachment for Moon disks is three Dzus fasteners.

EcoModder Forum > EcoModding > Aerodynamics
> DZUS fastened MOON DISC wheel covers?