Project: making a permanent Metro Kammback extension

[MetroMPG]

Phil: So far the MIB have been leaving me alone. Maybe they feel some affinity to me for driving a black car.

Schultz: good idea. I think I still have the mirror & mount from the red ForkenSwift car.

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Weather was pretty ideal this AM (light winds) so I headed out to my test route for an A-B-A comparison.

Unfortunately, the replacement cruise control crapped out before I finished the B runs. I kid you not. The first unit worked fine for a year (?) before becoming unresponsive; the second one worked for less than an hour. Same symptoms.

So here's the incomplete data @ 55 mph (88.5 km/h), where A = Kammback on; B = Kammback off. Units = mpg (US)

Run ... East ... West ... Average
A1 .... 60.9 ... 57.7 ... 59.3
A2 .... 60.4 ... 59.4 ... 59.9
A3 .... 61.2 ... 56.4 ... 58.8

Average of A runs = 59.3

B1 .... 57.2 ... 56.5 ... 56.9
B2 .... 57.6 ... 54.9 ... 56.3
... cruise control stops working ...

Average of B runs = 56.6

No conclusions should really be drawn from this, because it's incomplete. But looking @ just the available figures, the Kammback runs were 4.9% better than the non-Kammback runs.

I really ought to get something to measure sound as well, because there seemed to be a noticeable difference in wind noise between the A & B runs.

[MazdaMatt]

I'm starting to consider this a plausible addition to my protege5 hatchback... I like the plexi one next door.

[aerohead]

Darin,the incomplete data set looks very promising.I would like to think that after the cruise-control issues(bummer!) are resolved,that the mpg trend will resurface.The Metro looks really good.If bondo lived down the street,he could pull a mold off the back of the car and reproductions could be layed-up for those with Metros that don't have the facility to do it themselves.If I didn't know what was going on,and just saw your car in passing,I'd presume it was an OEM or SEMA aftermarket part.Seamless!

[Big Dave]

Noise can be a surrogate parameter for turbulent drag. Turbulence is noisy.

Much lower noise was how I knew I wason the right track with my bed cover. That funky-looking thing I have is very quiet. An open bed roars at you.

[trebuchet03]

ooo - I totally missed this thread

Metro, some reading for you on moldless sandwich construction by Burt Rutan (you know, the spaceshipOne guy )
http://www.actechbooks.com/products/act431/

Unfortunately, I haven't found a digital copy - check your library.

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As for your earlier comment on the black paint showing ripples and such... You're totally right - it's just more time (and some fairing putty) to get it smooth. Using proper sanding implements (sandpaper glued to a long straight 2x4 and implements that match the curvature of your rounds) helps a whole lot - necessary, even.

Because I'm thinking about it (recently saw this in application) - a cheap way to add stiffeners to compound curves is to use foam tape or adhesive weather stripping - then glass over that. The foam conforms nicely and is available in a bunch of thicknesses (bonus for lightweight and cheap)

It looks great though - congratulations Of course, the creator is also the most critical.

And if you didn't think about this already - you now have a working prototype to make a mold and tool from I'm not precisely sure how big the market would be though

[hamorhead]

could someone do the ideal teardrop thing with a 92-95 civic hatch thats stock (not the aerocivic)